阅读说明：本技术 光接收装置、站侧装置、pon系统、前置放大器、光接收方法及积分器的输出反转抑制方法 (Optical receiver, station-side device, PON system, preamplifier, optical receiving method, and method for suppressing output inversion of integrator ) 是由 田中成斗 于 2020-06-08 设计创作，主要内容包括：一种接收突发式的光信号的光接收装置,包括：受光元件,接收光信号；放大器,接收并放大基于来自受光元件的输入电流的电流；直流调整电路,与从受光元件到放大器的输入电路连接,去除输入电流中包含的失调电流；交流调整电路,与输入电路连接,输入电流的一部分流过所述交流调整电路；及控制部,基于放大器的输出及参考电压来控制直流调整电路及交流调整电路,控制部包括：积分器,对放大器的输出进行积分,并输出到正相及反相的两个电路；及反转抑制电路,在积分器的输出的反相电位高于正相电位时,以向正相注入电流且从反相抽出电流的方式进行动作。(An optical receiving device for receiving a burst-mode optical signal, comprising: a light receiving element that receives a light signal; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, for removing an offset current included in the input current; an alternating current adjustment circuit connected to the input circuit, wherein a part of the input current flows through the alternating current adjustment circuit; and a control unit for controlling the DC adjustment circuit and the AC adjustment circuit based on the output of the amplifier and the reference voltage, the control unit including: an integrator for integrating the output of the amplifier and outputting the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when the negative phase potential of the output of the integrator is higher than the positive phase potential.)

1. An optical receiving device for receiving burst optical signals, wherein,

the light receiving device includes:

a light receiving element that receives the optical signal;

an amplifier that receives and amplifies a current based on an input current from the light receiving element;

a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current;

an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and

a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage,

the control section includes:

an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and

and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

2. The light receiving device according to claim 1,

the inversion suppressing circuit injects a current and extracts a current equal to each other.

3. The light receiving device according to claim 1 or 2,

the inversion suppressing circuit includes:

a transconductance amplifier converting a voltage based on the positive-phase and negative-phase potential difference output from the integrator into a current and outputting the current; and

and a current mirror circuit that generates a current to be injected into the positive phase and a current to be extracted from the negative phase based on an output of the transconductance amplifier.

4. The light receiving device according to any one of claims 1 to 3,

adding a negative offset voltage to the reference voltage.

5. The light receiving device according to any one of claims 1 to 4,

when the positive-phase potential is higher than the negative-phase potential, the inversion suppressing circuit does not perform an operation of injecting a current into the positive phase and extracting a current from the negative phase.

6. A station-side device connected to a plurality of terminal devices via an optical transmission path using an optical fiber,

the station-side device includes:

a light receiving element for receiving a burst optical signal from the terminal device;

an amplifier that receives and amplifies a current based on an input current from the light receiving element;

a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current;

an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and

a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage,

the control section includes:

an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and

and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

7. A PON system is provided with:

a plurality of terminal devices;

an optical transmission path using an optical fiber; and

a station-side device that communicates with the plurality of terminal devices via the optical transmission path, wherein,

the light receiving device mounted on at least the station-side device of the terminal device and the station-side device includes:

a light receiving element for receiving a burst optical signal from the terminal device;

an amplifier that receives and amplifies a current based on an input current from the light receiving element;

a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current;

an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and

a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage,

the control section includes:

an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and

and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

8. A preamplifier is provided with:

an amplifier that receives and amplifies a current based on an input current from a light receiving element that receives a burst-type optical signal;

a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current;

an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and

a control unit that controls the DC adjustment circuit and the AC adjustment circuit based on an output of the amplifier and a reference voltage,

the control section includes:

an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and

and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

9. An optical receiving method for receiving burst optical signals, wherein, in a pre-amplification stage,

receiving a current based on an input current from a light receiving element that receives the optical signal and amplifying the current by an amplifier,

removing an offset current included in the input current and discharging a part of the input current based on an output of the amplifier and a reference voltage,

the output of the amplifier is integrated by an integrator and is output to two circuits of a positive phase and a negative phase, and when a potential of the negative phase output to the two circuits is higher than a potential of the positive phase, a current is injected into the positive phase and a current is extracted from the negative phase.

10. A method for suppressing output inversion of an integrator in a preamplifier for light reception,

receiving and amplifying a current based on an input current from a light receiving element that receives a burst-type optical signal,

removing an offset current included in the input current based on the amplified output and a reference voltage, and releasing a part of the input current,

the output is integrated by the integrator and output to two circuits of a positive phase and a negative phase, and when a potential of the negative phase output to the two circuits is higher than a potential of the positive phase, a current is injected into the positive phase and a current is extracted from the negative phase.

Technical Field

The present disclosure relates to a light receiving device, a station-side device, a PON system, a preamplifier, a light receiving method, and an output inversion suppressing method for an integrator.

The present application claims priority of japanese application No. 2019-110446, which was filed on 6/13/2019, and cites the entire contents of the description in said japanese application.

Background

In a light receiving device for receiving light, a burst-type optical signal received by a photodiode is output as a differential signal via a preamplifier (TIA: trans Amplifier) (see, for example, patent document 1). A station-side device of a PON (Passive Optical Network) system is connected to a plurality of terminal devices (home-side devices) via Optical fibers. Therefore, the distance from the terminal device to the station-side device is not uniform, and the intensity of the optical signal reaching the optical receiving device mounted on the station-side device greatly varies for each terminal device.

Therefore, an adjustment circuit is provided that discharges (or extracts) a part of the current converted by the photodiode, and when the intensity of the optical signal is high, the adjustment circuit discharges a part of the current, and when the intensity of the optical signal is weak, the adjustment circuit stops the discharging function (see, for example, patent documents 2 and 3). It is considered that in order to stop the release, it can be realized by applying a negative offset voltage to the reference voltage so as to be lower than the output of the amplification stage. When a part of the current is discharged, the closed-loop control is performed, and when the discharge function is stopped, the open-loop control is performed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-250137

Patent document 2: japanese patent laid-open publication No. 2012 and 60436

Patent document 3: international publication WO2016/035374A1

Disclosure of Invention

Means for solving the problems

The present disclosure includes the following inventions. However, the invention is defined by the claims.

(light receiving device)

The present disclosure relates to an optical receiving device for receiving a burst-type optical signal, the optical receiving device including: a light receiving element that receives the optical signal; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

(standing side device)

The present disclosure is a station-side device connected to a plurality of terminal devices via an optical transmission path using an optical fiber, the station-side device including: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

(PON System)

The disclosed PON system is provided with: a plurality of terminal devices; an optical transmission path using an optical fiber; and a station-side device that communicates with the plurality of terminal devices via the optical transmission path, wherein at least the station-side device of the terminal devices and the station-side device includes: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

(Pre-amplifier)

The disclosed preamplifier is provided with: an amplifier that receives and amplifies a current based on an input current from a light receiving element that receives a burst-type optical signal; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

(light receiving method)

An optical receiving method for receiving a burst-type optical signal, wherein, in a pre-amplification stage, a current based on an input current from a light receiving element is received and amplified by an amplifier, the light receiving element receives the optical signal, an offset current included in the input current is removed based on an output of the amplifier and a reference voltage, a part of the input current is discharged, an output of the amplifier is integrated by an integrator and output to two circuits of a positive phase and a negative phase, and when a reverse phase potential output to the two circuits is higher than a positive phase potential, a current is injected into the positive phase and a current is extracted from the reverse phase.

(output inversion suppressing method of integrator)

The present disclosure relates to a method for suppressing output inversion of an integrator in a preamplifier for optical reception, wherein a current based on an input current from a light receiving element is received and amplified, the light receiving element receives a burst optical signal, an offset current included in the input current is removed based on an amplified output and a reference voltage, a part of the input current is discharged, the output is integrated by the integrator and output to two circuits of a positive phase and a negative phase, and when a reverse phase potential output to the two circuits is higher than a positive phase potential, a current is injected into the positive phase and a current is extracted from the reverse phase.

Drawings

Fig. 1 is a connection diagram of a PON system according to an embodiment.

Fig. 2 is a diagram showing an example of a circuit configuration of the light receiving device, and particularly, a diagram centering on a preamplifier portion.

Fig. 3 is a diagram showing an internal circuit of the inversion suppressing circuit of fig. 2.

Fig. 4 is a graph showing an example of integrator output inversion in the open loop as a result of DC analysis (static characteristic analysis).

Fig. 5 is a graph showing an example of a delay in transient response due to inversion of integrator output as a result of transient analysis.

Fig. 6 is a graph showing an example of integrator output inversion in the open loop as a result of DC analysis (static characteristic analysis).

Fig. 7 is a graph showing an example of the result of transient analysis.

Fig. 8 is an example of a graph showing how the amplification factor of the amplifier to which the inversion suppression circuit is added exhibits frequency characteristics with respect to input currents of various magnitudes.

Detailed Description

[ problems to be solved by the present disclosure ]

When the negative offset voltage applied to the reference voltage is increased, the positive and negative outputs of the integrator may be inverted, and the potential difference may be increased. In such a case, there are cases where transient response to a burst is delayed and normal reception of an optical signal fails.

In view of the above problem, an object of the present disclosure is to suppress inversion of an output of an integrator in an optical receiving device that receives a burst optical signal.

[ Effect of the present disclosure ]

According to the present disclosure, it is possible to suppress inversion of the output of the integrator in the optical receiving device that receives the burst optical signal.

[ description of embodiments of the present disclosure ]

The embodiments of the present disclosure include at least the following as the gist thereof.

(1) Disclosed as an optical receiving device is an optical receiving device that receives a burst-mode optical signal, and that is provided with: a light receiving element that receives the optical signal; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

In such a light receiving device, when the output of the integrator is inverted and the reverse-phase potential is higher than the normal-phase potential, the inversion suppressing circuit can operate to inject a current into the normal phase and extract a current from the reverse phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator in the optical receiving device that receives the burst optical signal can be suppressed.

(2) In the light receiving device described in (1), it is preferable that the inversion suppressing circuit injects a current and extracts a current equal to each other.

In this case, since the injected current and the extracted current are equal to each other, the common potential of the output of the integrator does not change.

(3) In the optical receiving device according to the above (1) or (2), the inversion suppressing circuit may include: a transconductance amplifier converting a voltage based on the positive-phase and negative-phase potential difference output from the integrator into a current and outputting the current; and a current mirror circuit that generates a current to be injected into the positive phase and a current to be extracted from the negative phase based on an output of the transconductance amplifier.

In this case, when the positive-phase potential is higher than the negative-phase potential of the output of the integrator, the inversion suppression circuit neither injects nor extracts a current. When a state in which the inverted potential of the output of the integrator is higher than the positive potential, that is, when inversion of the potential starts to occur, a current for suppressing the state can be immediately generated by the current mirror circuit.

(4) In the light receiving device described in any one of (1) to (3), for example, a negative offset voltage is added to the reference voltage.

If there is a difference in intensity, for example, if the intensity is relatively weak, in the burst-type optical signal, if a negative offset voltage is not applied to the reference voltage, even if the positive offset voltage slightly increases, the noise may increase due to the current drawn by the dc adjustment circuit. Therefore, it is not preferable to lower the negative offset voltage, and it is preferable to apply a sufficient negative offset voltage.

(5) In the light receiving device described in any one of (1) to (4), for example, when the positive phase potential is higher than the negative phase potential, the inversion suppressing circuit does not perform an operation of injecting a current into the positive phase and extracting a current from the negative phase.

When the positive-phase potential is higher than the negative-phase potential, the inversion suppression circuit does not perform an unnecessary operation.

(6) A station-side apparatus connected to a plurality of terminal apparatuses via an optical transmission path using an optical fiber, the station-side apparatus comprising: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

In such a station-side device, when the output of the integrator is inverted to a state in which the inverted potential is higher than the normal-phase potential, the inversion suppression circuit can operate to inject a current into the normal phase and extract a current from the inverted phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator in the station-side device that receives the burst optical signal can be suppressed.

(7) The PON system includes: a plurality of terminal devices; an optical transmission path using an optical fiber; and a station-side device that communicates with the plurality of terminal devices via the optical transmission path, wherein at least the station-side device of the terminal devices and the station-side device includes: a light receiving element for receiving a burst optical signal from the terminal device; an amplifier that receives and amplifies a current based on an input current from the light receiving element; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

In such a PON system, in the optical receiving apparatus in the station-side apparatus, when the output of the integrator is inverted to a state in which the inverted potential is higher than the normal-phase potential, the inversion suppressing circuit can operate so as to inject a current into the normal phase and extract a current from the inverted phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator in the optical receiving device that receives the burst optical signal can be suppressed.

(8) The preamplifier includes: an amplifier that receives and amplifies a current based on an input current from a light receiving element that receives a burst-type optical signal; a direct current adjustment circuit connected to an input circuit from the light receiving element to the amplifier, the direct current adjustment circuit removing an offset current included in the input current; an ac adjustment circuit connected to the input circuit, wherein a part of the input current flows through the ac adjustment circuit; and a control unit that controls the dc adjustment circuit and the ac adjustment circuit based on an output of the amplifier and a reference voltage, the control unit including: an integrator that integrates the output of the amplifier and outputs the integrated output to two circuits of a positive phase and a negative phase; and an inversion suppressing circuit that operates to inject a current into the positive phase and extract a current from the negative phase when a negative phase potential of an output of the integrator is higher than a positive phase potential.

In such a preamplifier, when the output of the integrator is inverted to a state in which the inverted potential is higher than the normal-phase potential, the inversion suppressing circuit can operate to inject a current into the normal phase and extract a current from the inverted phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator when receiving the burst optical signal can be suppressed.

(9) The optical receiving method is an optical receiving method for receiving a burst-type optical signal, wherein, in a pre-amplification stage, a current based on an input current from a light receiving element is received and amplified by an amplifier, the light receiving element receives the optical signal, an offset current included in the input current is removed based on an output of the amplifier and a reference voltage, a part of the input current is discharged, an output of the amplifier is integrated by an integrator and output to two circuits of a positive phase and a negative phase, and when a reverse phase potential output to the two circuits is higher than a positive phase potential, a current is injected into the positive phase and a current is extracted from the reverse phase.

According to such a light receiving method, when the output of the integrator is inverted and the inverted potential is higher than the normal phase potential, it is possible to inject a current into the normal phase and extract a current from the inverted phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator when receiving the burst optical signal can be suppressed.

(10) An output inversion suppressing method of an integrator in a pre-amplifier for optical reception includes receiving and amplifying a current based on an input current from a light receiving element that receives a burst optical signal, removing an offset current included in the input current based on an amplified output and a reference voltage, discharging a part of the input current, integrating the output by the integrator, outputting the integrated output to two circuits of a positive phase and a negative phase, and injecting a current into the positive phase and extracting a current from the negative phase when a negative phase potential output to the two circuits is higher than a positive phase potential.

According to such an output inversion suppressing method, when the output of the integrator is inverted and the inverted potential is higher than the normal phase potential, it is possible to inject a current into the normal phase and extract a current from the inverted phase. Thereby, inversion of the output of the integrator is suppressed. Therefore, even when a sufficient negative offset voltage is applied, the inversion and expansion of the potential difference of the output of the integrator can be suppressed. In this way, inversion of the output of the integrator when receiving the burst optical signal can be suppressed.

[ details of embodiments of the present disclosure ]

Specific examples of the present disclosure are described below with reference to the drawings.

PON System

Fig. 1 is a connection diagram of a PON system 100 according to an embodiment. In the figure, a station side device (OLT: Optical Line Terminal) 1 is set as an aggregation station for a plurality of end devices (ONU: Optical Network Unit: 2, 3, 4 connected in a relationship of P2MP (Point to Multipoint). The terminal apparatuses 2, 3, and 4 are installed in the respective subscriber houses of the PON system 100. In this system, an optical fiber network is configured in which 1 optical fiber (trunk) 5 connected to a station-side device 1 is branched into a plurality of optical fibers (branch fibers) 7, 8, and 9 via an optical coupler 6. The number of terminal devices is merely an example for convenience of illustration, and is actually larger.

Between the station-side apparatus 1 and the terminal apparatuses 2, 3, and 4, uplink communication from the terminal apparatuses 2, 3, and 4 to the station-side apparatus 1 and downlink communication from the station-side apparatus 1 to the terminal apparatuses 2, 3, and 4 are possible. The distances from the optical coupler 6 to the respective terminal devices 2, 3, and 4 are not uniform, and have a difference in distance. Therefore, the optical signals arriving from the terminal devices 2, 3, and 4 at the station-side device 1 have a difference in intensity. The station-side device 1 is mounted with a line card 1a including an optical receiver.

Optical receiver

Fig. 2 is a diagram showing an example of the circuit configuration of the light receiving device 10, and particularly, is a diagram centering on the preamplifier 11. The light receiving device 10 is a device that receives burst-type optical signals (hereinafter, simply referred to as bursts) transmitted from the terminal devices 2, 3, and 4, and includes an avalanche photodiode 12 as a light receiving element, an amplifier 13, a dc adjustment circuit 14, an ac adjustment circuit 15, a control unit 16, a differential circuit 17, a detection circuit 18, and a reference potential generation circuit 19. The outputs (Vout, Voutb) of the preamplifier 11 are transmitted to the subsequent-stage circuit 21 via the AC coupling of the capacitor 2.

The avalanche photodiode 12, to which the voltage VPD is applied to the cathode, converts the optical signal into a current. The amplifier 13 receives and amplifies a current based on an input current from the avalanche photodiode 12, and outputs a voltage Va. The dc adjustment circuit 14 connected to the input circuit L from the avalanche photodiode 12 to the amplifier 13 has a current mirror circuit of MOSFETs (Metal-Oxide-Semiconductor-Field-Effect-transistors, hereinafter referred to as MOS transistors) M0, M1.

The dc adjustment circuit 14 removes the offset current Iaoc from the input current Iin from the avalanche photodiode 12. Similarly, the ac adjustment circuit 15 connected to the input circuit L includes a MOS transistor M3. The ac adjustment circuit 15 has a function of flowing (discharging) a part of the current Iin (current Iagc) input from the avalanche photodiode 12 without sending it to the amplifier 13. Thus, the current Iin is divided into a current Iaoc, a current Iagc, and an input current to the amplifier 13.

The control unit 16 includes an integrator 161, an inversion suppressing circuit 162, a Transconductance amplifier (hereinafter referred to as ota (operational transmission amplifier)) 163, a current control unit 164, and a MOS transistor M2. A reference voltage including a negative offset voltage is supplied from the reference potential generating circuit 19 to the integrator 161, the differential circuit 17, and the MOS transistors M2 and M3. The negative offset voltage allows the ac regulator circuit 15 and the dc regulator circuit 14 to operate for a strong input burst, but prevents the ac regulator circuit 15 and the dc regulator circuit 14 from operating for a weak input burst.

The integrator 161 integrates the output of the amplifier 13 and outputs the integrated output to two circuits of a positive phase P and a negative phase N. The output of integrator 161 is provided to current control section 164 via OTA 163. OTA163 has circuitry that changes the amplification according to the input. The current control unit 164 sets an input current range for adjustment of the amplification degree. The detection circuit 18 has a function of detecting an output from the differential circuit 17 and switching a time constant of the integrator 161 in order to cope with a strong input burst. The current control unit 164 controls the current mirror circuits of the MOS transistors M2 and M3 and the current mirror circuits of the MOS transistors M0 and M1.

Fig. 3 is a diagram showing an internal circuit of the inversion suppressing circuit 162 in fig. 2. In fig. 3, the inversion suppressing circuit 162 includes an OTA162A, PNP MOS transistors M11, M12, and M13 constituting a current mirror circuit 162B, and NPN MOS transistors M14 and M15 constituting another current mirror circuit 162C. The control power supply voltage Vcc is supplied to the source sides of the MOS transistors M14, M15. The source sides of the MOS transistors M11, M12, M13 are connected to GND.

The OTA162A operates according to the positive phase potential Vp and the negative phase potential Vn input from the integrator 161. Specifically, when Vp is greater than or equal to Vn, OTA162A does not operate. When the reverse potential Vn is higher than the normal potential Vp and the reverse potential difference exceeds a predetermined reference value, the OTA162A operates. This operation is to generate a positive output current proportional to the potential difference obtained by subtracting the reference value from the reversed potential difference. According to the generated current, the current Ip is injected into the positive phase P and the current In is extracted from the negative phase N by the current mirror circuit 162B based on the MOS transistors M11, M12, and M13 and the current mirror circuit 162C based on the MOS transistors M14 and M15.

In the light receiving device 10 including such an inversion suppressing circuit 162, when the output of the integrator 161 is inverted and the inverted potential Vn is higher than the normal phase potential Vp (strictly speaking, a state higher than the reference value), the inversion suppressing circuit 162 operates to inject a current into the normal phase P and extract a current from the inverted phase N. Thereby, inversion of the output of the integrator 161 is suppressed. Therefore, even when a sufficient negative offset voltage is applied to the reference voltage generated by the reference potential generation circuit 19, the inversion and expansion of the potential difference of the output of the integrator 161 can be suppressed.

In addition, the same current In flows through the MOS transistors M11, M12, and M13 by the operation of the current mirror circuit 162B based on the MOS transistors M11, M12, and M13. As a result, the same amount of current Ip as the current In flows also to the MOS transistor M14, and the current Ip flows to the MOS transistor M15 by the operation of the current mirror circuit 162C based on the MOS transistors M14 and M15. That is, the current Ip injected into the positive phase P by the inversion suppressing circuit 162 and the current In extracted from the negative phase N are equal to each other. Thus, since the injected current and the extracted current are equal to each other, the common potential of the output of the integrator 161 does not change.

In addition, the OTA162A of the inversion suppressing circuit 162 converts the voltage based on the potential difference of the positive phase and the negative phase output from the integrator 161 into a current and outputs the current. Current mirror circuits 162B, 162C generate a current injected into the positive phase and a current extracted from the negative phase based on the output of OTA 162A. In this case, when the positive-phase potential Vp is higher than the negative-phase potential Vn output from the integrator 161, the inversion suppression circuit 162 neither injects nor extracts a current. In other words, no useless operation is performed. When a state in which the reverse-phase potential Vn of the output of the integrator 161 is higher than the normal-phase potential Vp, that is, when inversion of the potential starts to occur, a current for suppressing this can be immediately generated by the current mirror circuits 162B and 162C.

The operation and effect of the inversion suppressing circuit 162 will be described below with reference to a graph. First, for comparison, a case where the inversion suppressing circuit 162 is not provided will be described.

"case without inversion suppressing Circuit

(inversion of integrator output in open Loop)

Fig. 4 is a graph showing an example of integrator output inversion in the open loop as a result of DC analysis (static characteristic analysis). (a) The voltage (dotted line) output from the amplifier 13 and the reference voltage (solid line) to which the negative offset voltage (40mV) is added are shown. (b) A positive phase potential (solid line) and a negative phase potential (broken line) representing the output of the integrator 161. (c) The gate potential (broken line) of the MOS transistor M3 of the ac adjustment circuit 15 and the gate potentials (solid line) of the MOS transistors M0 and M1 of the dc adjustment circuit 14 are shown. (d) Representing the offset current of the removed direct current. The horizontal axis is a logarithmic scale of the input current (Iin) common from (a) to (d).

In the current range (from 10) with small input current^-5[A]A vertical one-dot chain line in the figure), a negative offset voltage acts, the direct current adjustment circuit 14 and the alternating current adjustment circuit 15 do not function, and current extraction from AC and DC from the input current is not performed (hereinafter, the extracted current is referred to as "current extraction"). ). The dc adjustment circuit 14 and the ac adjustment circuit 15 draw out a current for an input current equal to or larger than the dashed-dotted line. Here, as can be seen from the graph of (b), when the input current is smaller than the one-dot chain line, the output of the integrator 161 existsThe positive phase potential and the negative phase potential are largely inverted.

Next, fig. 5 is a graph showing an example of a delay in transient response due to inversion of the integrator output as a result of transient analysis. In the figure, (a) shows an input current (Iin) from the avalanche photodiode 12 when an optical signal coming from a weak input burst after a strong input burst is received. (b) The inverted amplified output (burst waveform) of the amplifier 13 with respect to the input voltage and-40 mV (linear portion) as a reference voltage are shown. (c) A positive phase potential (solid line) and a negative phase potential (broken line) representing the output of the integrator 161. (d) The upper line of the two lines is the source voltage of the AC current extracting MOS transistor M3, and the two lower lines, which are visible as an overlap, are the gate voltage of the AC current extracting MOS transistor M3 and the gate voltages of the DC current extracting MOS transistors M0 and M1. The lower line is the level of GND. (e) The two lines are always substantially overlapped, one of the lines accompanied by vertical minute vibration is a DC extraction current, and the other of the lines is an AC extraction current. (f) Which represents the input voltage to the subsequent stage circuit 21. The horizontal axis represents time common from (a) to (f).

When attention is paid to fig. 5 (c), the state is always in the inverted state, and as indicated by the broken line of the ellipse, the burst ends in a state where the strong input burst cannot be disengaged from the inverted state. Therefore, the light receiving device 10 is in a state where the ring is always open. When focusing on (d), the lower line is attached to GND, and current extraction is not performed. When focusing on (e), the current extraction is also substantially not performed. According to fig. 5, when the output of the integrator 161 is inverted, the output cannot be deviated from the inversion, and a delay in transient response may occur.

In addition, when a negative offset Voltage is not applied to the reference Voltage, even in a weak input burst under PVT (Process-Voltage-Temperature) condition in which a positive offset Voltage slightly increases, current extraction occurs in a closed loop, and noise may increase. Therefore, it is not preferable to lower the negative offset voltage, and it is preferable to apply a sufficient negative offset voltage. Further, a function is required that does not expand the reverse potential difference between the positive phase potential and the negative phase potential of the output of the integrator 161 even if a sufficient negative offset voltage is supplied. The inversion suppression circuit 162 is a countermeasure against this demand.

Case where there is an inversion suppressing circuit

Fig. 6 is a graph showing an example of integrator output inversion in the open loop as a result of DC analysis (static characteristic analysis). (a) The voltage (dotted line) output from the amplifier 13 and the reference voltage (solid line) to which the negative offset voltage (40mV) is added are shown. (b) A positive phase potential (solid line) and a negative phase potential (broken line) representing the output of the integrator 161. (c) The gate potential (broken line) of the MOS transistor M3 of the ac adjustment circuit 15 and the gate potentials (solid line) of the MOS transistors M0 and M1 of the dc adjustment circuit 14 are shown. (d) Representing the offset current of the removed direct current. (e) A current (solid line) injected into the positive phase and a current (broken line, merging with the solid line from the middle) extracted from the negative phase in order to suppress the reverse rotation of the output of the integrator 161 are shown. The horizontal axis is a logarithmic scale of the input current (Iin) common from (a) to (e). The vertical one-dot chain line in the figure indicates the position of the input current of about 90 μ a.

As shown in FIG. 6 (e), a current of 10 μ A (10) is inputted^-5A) In the weak input range of 90 μ a, a current is injected into the positive phase, and an equal amount of current is extracted from the negative phase. As a result, as seen from the waveform of (b), even in the case where a negative offset voltage is applied, large inversion of the output of the integrator 161 in a weak input range is suppressed.

Fig. 7 is a graph showing an example of the result of transient analysis. In the figure, (a) shows an input current (Iin) from the avalanche photodiode 12 when an optical signal coming from a weak input burst after a strong input burst is received. (b) The inverted amplified output (burst waveform) of the amplifier 13 with respect to the input voltage and-40 mV (linear portion) as a reference voltage are shown. (c) shows the positive phase potential (solid line) and the negative phase potential (broken line) of the output of the integrator 161. In (d), the upper line is the source voltage of the AC current extracting MOS transistor M3, the middle line is the gate voltage of the DC current extracting MOS transistors M0, M1, and the lower line is the gate voltage of the AC current extracting MOS transistor M3. (e) The upper line has a large change in the DC extraction current, and the lower line has an AC extraction current. And (f) represents an input voltage to the subsequent stage circuit 21. The horizontal axis represents time common from (a) to (f).

In fig. 7, focusing on (c), the burst is deviated from the inverted state within about 0.2 μ sec (200 n sec) from the beginning of the first burst, which is indicated by a dashed circle mark. As can be seen from comparison with fig. 5, which cannot be disengaged from the inverted state before the burst, the delay of the transient response is significantly improved and reduced.

Then, the inversion state of the integrator output is generated for the weak input burst, but the gate voltages of the MOS transistors M0 and M1 of the dc adjustment circuit 14 are maintained, and the closed loop is maintained. In (e), the DC extraction current is reduced with respect to the weak input burst, converging to a few μ a, but maintaining a closed loop.

Fig. 8 is an example of a graph showing how the amplification factor of the amplifier 13 after the inversion suppressing circuit 162 is added exhibits frequency characteristics with respect to input currents of various magnitudes. The upper double-dashed box is enlarged to show the lower diagram. The portion enclosed by the dashed ellipse in the lower graph indicates that feedback is applied (closed loop) even for weak input bursts smaller than 50 μ a.

Further, regarding the noise characteristics, when the closed-loop operation is completely performed without adding a negative offset voltage to the input current (Iin)24 μ a which is an integrated value of the frequency band 25GHz, the effective value of the noise is 1.71 μ Arms. When the negative offset voltage is added without providing the inversion suppression circuit 162, the voltage becomes 1.52 μ Arms, and noise is reduced.

On the other hand, when the inversion suppression circuit 162 is provided, the effective value of noise is 1.54 μ a for the same input current. Therefore, even if the inversion suppression circuit 162 is provided, the noise is sufficiently reduced by only 0.02 μ Arms compared to the case where the closed-loop operation is completely performed. This is considered to be that, when the loop is closed using the inversion suppressing circuit 162, the DC extraction current is small as several μ a, which has an influence.

As described above, by providing the inversion suppressing circuit 162, it is possible to reduce the delay of the transient response and to continue the closed loop without increasing the noise under the condition that the reference voltage to which the negative offset voltage is added is lower than the output voltage of the amplifier 13.

(others)

The light receiving device 10 disclosed above is provided in the station-side device 1, but may be provided in the terminal devices 2, 3, and 4.

Supplement to memory

The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Description of the reference numerals

1 station side device

1a line card

2. 3, 4 terminal device

5 optical fiber

6 optical coupler

7. 8, 9 optical fiber

10 light receiving device

11 preamplifier

12 avalanche photodiode

13 Amplifier

14 DC regulation circuit

15 AC regulating circuit

16 control part

17 differential circuit

18 detection circuit

19 reference potential generating circuit

20 capacitor

21 latter stage circuit

100 PON system

161 integrator

162 inversion suppression circuit

162A transconductance amplifier (OTA)

162B, 162C current mirror circuit

163 transconductance amplifier (OTA)

164 Current control part

L input circuit

M0, M1, M2 and M3 MOS transistors

M11, M12, M13, M14 and M15 MOS transistors

N inverse phase

P normal phase