阅读说明：本技术 一种光纤传输链路中接收底噪的优化系统及方法 (Optimization system and method for receiving background noise in optical fiber transmission link ) 是由 王波 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种光纤传输链路中接收底噪的优化系统及方法,属于模拟信号的光纤传输技术领域,系统包括发射端和接收端,所述发射端包括用于对信号高频段增益进行补偿的增益补偿电路,所述接收端包括用于对信号高频段增益进行压缩的增益压缩电路。本发明系统发射端包括一增益补偿电路,接收端包括一增益压缩电路,增益补偿电路对信号高频段增益进行补偿,增益压缩电路对信号高频段增益进行压缩,以使高频段的输出底噪相比原光纤链路下降,进而使得系统的信号平坦度小,信噪比高,保证了通信质量。(The invention discloses an optimization system and method for receiving background noise in an optical fiber transmission link, belonging to the technical field of optical fiber transmission of analog signals. The system transmitting end comprises a gain compensation circuit, the receiving end comprises a gain compression circuit, the gain compensation circuit compensates the signal high-frequency band gain, and the gain compression circuit compresses the signal high-frequency band gain so as to reduce the output bottom noise of the high-frequency band compared with the original optical fiber link, thereby ensuring the signal flatness of the system to be small, the signal-to-noise ratio to be high and ensuring the communication quality.)

1. An optimization system for receiving background noise in an optical fiber transmission link is characterized in that: the system comprises a transmitting end and a receiving end, wherein the transmitting end comprises a gain compensation circuit for compensating the signal high-frequency gain, and the receiving end comprises a gain compression circuit for compressing the signal high-frequency gain.

2. The system of claim 1, wherein the system is configured to optimize reception noise in an optical transmission link, and wherein: the gain compensation circuit includes a first broadband amplifier and a first feedback circuit, and the gain compression circuit includes a second broadband amplifier and a second feedback circuit.

3. The system of claim 2, wherein the system is configured to optimize reception noise in an optical transmission link, and further configured to: the first feedback circuit comprises a first resistor, a second resistor and a first capacitor;

one end of the second resistor is connected to the input end of the first broadband amplifier, the other end of the second resistor is connected to one end of the first resistor, the other end of the first resistor is connected to the output end of the first broadband amplifier, and the first capacitor is connected with the first resistor in parallel.

4. The system of claim 2, wherein the system is configured to optimize reception noise in an optical transmission link, and further configured to: the second feedback circuit comprises a third resistor, a fourth resistor and a third capacitor;

one end of the third resistor is connected to the input end of the second broadband amplifier, the other end of the third resistor is connected to the output end of the second broadband amplifier, and the fourth resistor is connected with the third capacitor in series and then connected with the third resistor in parallel.

5. The system of claim 2, wherein the system is configured to optimize reception noise in an optical transmission link, and further configured to: the gain compression circuit further comprises a first temperature-compensated attenuator, and the first temperature-compensated attenuator is arranged at the output end of the second broadband amplifier.

6. The system of claim 1, wherein the system is configured to optimize reception noise in an optical transmission link, and wherein: the gain compensation circuit comprises a third broadband amplifier, an equalizer, a first attenuator and a DC isolator which are connected in sequence; the gain compression circuit comprises a fourth broadband amplifier, a second attenuator and a second temperature compensation attenuator which are connected in sequence.

7. The system of claim 6, wherein the system is configured to optimize reception noise in an optical transmission link, and further comprising: the fourth broadband amplifier comprises an amplifier with flat full-band response and a low-pass filter which are sequentially connected.

8. The system of claim 1, wherein the system is configured to optimize reception noise in an optical transmission link, and wherein: the transmitting terminal further comprises a laser connected with the output end of the gain compensation circuit, the receiving terminal further comprises a photoelectric detector and a low-noise amplifier which are sequentially connected, the output end of the low-noise amplifier is connected with the gain compression circuit, and the transmitting terminal is connected with the receiving terminal through an optical cable.

9. A method for optimizing a system for receiving background noise in an optical fiber transmission link is characterized in that: the method comprises the following steps:

a gain compensation circuit is arranged at the transmitting end and used for compensating the gain of the high-frequency band of the signal;

and a gain compression circuit is arranged at the receiving end and is used for compressing the signal high-frequency band gain.

10. The method of claim 9, wherein the method comprises the steps of: the gain compensation circuit comprises a first broadband amplifier and a first feedback circuit, the gain compression circuit comprises a second broadband amplifier and a second feedback circuit, and the method further comprises:

and adjusting parameters of the first feedback circuit and the second feedback circuit to make the gain slope of the gain compensation circuit and the gain slope of the gain compensation circuit be opposite numbers.

Technical Field

The invention relates to the technical field of optical fiber transmission of analog signals, in particular to a system and a method for optimizing receiving background noise in an optical fiber transmission link.

Background

In modern communication technology, the bandwidth requirements for analog electrical signals in optical fiber transmission links are increasing, reaching hundreds of megahertz or even gigahertz. The wider the bandwidth is, the higher the sum of the received background noises, especially the background noises in the high frequency band have the greatest influence. However, the background noise of the laser device in the high frequency band is higher than that in the medium and low frequency bands, and generally in a link with a bandwidth of gigahertz order, the background noise in the high frequency band is higher than that in the low frequency band by several decibels, so that optimizing the noise in the high frequency band has an important significance on the background noise of the system, especially in the test application of a complex electromagnetic field environment with higher requirements.

In the existing optical fiber transmission link, the optimization of the bottom noise is realized by simultaneously reducing the bottom noise of the whole frequency band at the receiving end, for example, a low-noise broadband amplifier, a device for reducing the transmitting optical power and the like are adopted to optimize the bottom noise of the whole frequency band at the receiving end so as to ensure that the flatness of a system signal is low and achieve a better signal-to-noise ratio, and only a technical scheme aiming at the high-frequency-band receiving low noise in the optical fiber transmission link is not proposed temporarily, on the basis, the invention provides an optimization system and a method aiming at the high-frequency-band bottom noise of the optical fiber transmission link.

Disclosure of Invention

The invention aims to solve the problem that the prior art can not optimize the medium-high frequency band receiving low noise in an optical fiber transmission link, and provides an optimization system for receiving the background noise in the optical fiber transmission link.

The purpose of the invention is realized by the following technical scheme: the system specifically comprises a transmitting end and a receiving end, wherein the transmitting end comprises a gain compensation circuit for compensating the signal high-frequency band gain, and the receiving end comprises a gain compression circuit for compressing the signal high-frequency band gain.

Specifically, the gain compensation circuit includes a first broadband amplifier and a first feedback circuit, and the gain compression circuit includes a second broadband amplifier and a second feedback circuit.

Specifically, the first feedback circuit comprises a first resistor, a second resistor and a first capacitor; one end of the second resistor is connected to the input end of the first broadband amplifier, the other end of the second resistor is connected to one end of the first resistor, the other end of the first resistor is connected to the output end of the first broadband amplifier, and the first capacitor is connected with the first resistor in parallel.

Specifically, the second feedback circuit includes a third resistor, a fourth resistor, and a third capacitor; one end of the third resistor is connected to the input end of the second broadband amplifier, the other end of the third resistor is connected to the output end of the second broadband amplifier, and the fourth resistor is connected with the third capacitor in series and then connected with the third resistor in parallel.

Specifically, the gain compression circuit further comprises a first temperature-compensated attenuator, and the first temperature-compensated attenuator is arranged at the output end of the second broadband amplifier.

Specifically, as another embodiment, the gain compensation circuit of the system of the present invention includes a third wideband amplifier, an equalizer, a first attenuator, and a dc-blocking device, which are connected in sequence; the gain compression circuit of the system comprises a fourth broadband amplifier, a second attenuator and a second temperature compensation attenuator which are connected in sequence. Specifically, the fourth broadband amplifier comprises an amplifier with a flat full-band response and a low-pass filter which are connected in sequence.

Specifically, the transmitting end further comprises a laser connected with the output end of the gain compensation circuit, the receiving end further comprises a photoelectric detector and a low-noise amplifier which are sequentially connected, the output end of the low-noise amplifier is connected with the gain compression circuit, and the transmitting end is connected with the receiving end through an optical cable.

The invention also includes a method for optimizing the system for receiving the background noise in the optical fiber transmission link, which specifically includes:

a gain compensation circuit is arranged at the transmitting end and used for compensating the gain of the high-frequency band of the signal;

and a gain compression circuit is arranged at the receiving end and is used for compressing the signal high-frequency band gain.

Specifically, the gain compensation circuit includes a first wideband amplifier and a first feedback circuit, the gain compression circuit includes a second wideband amplifier and a second feedback circuit, and the method further includes:

and adjusting parameters of the first feedback circuit and the second feedback circuit to make the gain slope of the gain compensation circuit and the gain slope of the gain compensation circuit be opposite numbers.

Compared with the prior art, the invention has the beneficial effects that:

(1) the system transmitting end comprises a gain compensation circuit, the receiving end comprises a gain compression circuit, the gain compensation circuit compensates the signal high-frequency band gain, and the gain compression circuit compresses the signal high-frequency band gain so as to reduce the output bottom noise of the high-frequency band compared with the original optical fiber link, thereby ensuring the signal flatness of the system to be small, the signal-to-noise ratio to be high and ensuring the communication quality.

(2) The first broadband amplifier is used for providing compensation gain, the first feedback circuit is used for adjusting the gain compensation quantity of the full-band signal, so that the low-band gain is lower, the high-band gain is high, and the compensation of the high-band gain of the signal is realized; the second broadband amplifier is used for amplifying weak signals, the second feedback circuit is used for adjusting the gain compensation quantity of full-band signals, the low-band gain is high, the high-band gain is reduced linearly, the output bottom noise of a high frequency band is reduced compared with that of an original optical fiber link, and the signal flatness of the system is small.

(3) The first resistor and the second resistor of the first feedback circuit are used for adjusting the static operating point of the first broadband amplifier so that the first broadband amplifier works in an amplifying state; the first capacitor is used for adjusting the gain slope, so that the gain of the low frequency band of the signal is lower, and the gain of the high frequency band of the signal is high.

(4) The third resistor in the second feedback circuit is used for adjusting the static working point of the second broadband amplifier so that the second broadband amplifier works in an amplification state, and meanwhile, the third resistor is also used for adjusting the full-band average gain; the fourth resistor is connected with the third capacitor in series and used for adjusting the gain slope, and the fourth resistor is used for reducing the Q value, so that the signal can be in a state of enabling the low-frequency-band gain to be high and enabling the high-frequency-band gain to be linearly reduced after passing through the gain compression circuit.

(5) The gain compression circuit also comprises a first temperature compensation attenuator which is used for compensating fluctuation influence of temperature change on the bottom noise.

(6) The gain compensation circuit comprises a third broadband amplifier, an equalizer, a first attenuator and a DC blocking device which are sequentially connected, wherein the third broadband amplifier is used for providing compensation gain, the equalizer attenuates a low frequency band greatly and attenuates a high frequency band little so as to ensure the gain compensation of a high frequency band of a signal, the first attenuator is used for enabling the gain compensation circuit to present a good impedance matching circuit, and the DC blocking device is used for protecting a static working point of a laser; the gain compression circuit comprises a fourth broadband amplifier, a second attenuator and a second temperature compensation attenuator which are sequentially connected, the fourth broadband amplifier is used for amplifying signals, the whole gain compression circuit has the frequency response characteristic that the gain at the low frequency end is higher and the gain at the high frequency end is linearly reduced, the second attenuator is used for enabling the gain compression circuit to have a good impedance matching circuit, and the second temperature compensation attenuator is used for compensating the fluctuation of bottom noise caused by high and low temperatures and improving the high and low temperature performance of the system gain.

(7) The fourth broadband amplifier comprises an amplifier with flat full-band response and a low-pass filter which are sequentially connected, and is beneficial to adjusting the gain of full-band signals, so that the whole gain compression circuit has the frequency response characteristic that the gain at a low frequency end is higher and the gain at a high frequency end is linearly reduced.

(8) The method comprises the steps that a gain compensation circuit is arranged at a transmitting end, a gain compression circuit is arranged at a receiving end, the gain compensation circuit compensates the gain of the high frequency band of the signal, and the gain compression circuit compresses the gain of the high frequency band of the signal, so that the output bottom noise of the high frequency band is reduced compared with that of the original optical fiber link, the signal flatness of the system is small, the signal-to-noise ratio is high, and the communication quality is guaranteed.

(9) The gain slope of the gain compensation circuit and the gain slope of the gain compensation circuit are opposite numbers, so that the gain flatness of the broadband signal is ensured, and the communication quality of the system is ensured.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the figure:

fig. 1 is a schematic circuit diagram of a gain compensation circuit according to embodiment 1 of the present invention;

fig. 2 is a schematic circuit diagram of a gain compression circuit according to embodiment 1 of the present invention;

FIG. 3 is a block diagram of a system according to embodiment 1 of the present invention;

fig. 4 is a schematic circuit diagram of a gain compensation circuit according to embodiment 2 of the present invention;

fig. 5 is a schematic circuit diagram of a gain compression circuit according to embodiment 2 of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like are directions or positional relationships described based on the drawings, and are only for convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

This implementation is for solving among the prior art can't receive the problem that low noise carries out the optimization to the high frequency channel in the optical transmission link, provide the optimization system that receives the end noise in the optical transmission link, the system includes transmitting terminal and receiving terminal, the transmitting terminal includes the gain compensating circuit who is used for carrying out the compensation to signal high frequency channel gain, make the low frequency channel gain lower, the high frequency channel gain is high, the receiving terminal includes the gain compression circuit who is used for carrying out the compression to signal high frequency channel gain, even the low frequency channel gain is high, the high frequency channel gain linearity reduces, make the output end noise of high frequency channel compare the former optical fiber link decline, full frequency channel low noise presents the flat trend, gain flatness has been guaranteed, it is little to make system signal flatness, the signal-to-noise ratio is high, communication quality has been guaranteed.

As an option, the gain compensation circuit includes a first broadband amplifier a1 and a first feedback circuit, and the gain compression circuit includes a second broadband amplifier a2 and a second feedback circuit. Specifically, the first broadband amplifier a1 is configured to provide a compensation gain amount, and the first feedback circuit is configured to adjust a gain compensation amount of a full-band signal, so that a low-band gain is relatively low, a high-band gain is high, and compensation of a high-band gain of the signal is achieved; the second broadband amplifier A2 is used for amplifying weak signals, and the second feedback circuit is used for adjusting the gain compensation quantity of full-band signals, so that the low-band gain is high, the high-band gain is linearly reduced, the output bottom noise of the high-band is reduced compared with the original optical fiber link, and the signal flatness of the system is small.

As an option, the wideband amplifier is embodied as a radio frequency transistor ATF54143 for providing an appropriate amount of compensation gain.

Further, as shown in fig. 1, the first feedback circuit includes a first resistor R1, a second resistor R2, and a first capacitor C1. Specifically, one end of a second resistor R2 is connected to the input end of the first broadband amplifier a1, the other end of the second resistor R2 is connected to one end of a first resistor R1, the other end of the first resistor R1 is connected to the output end of the first broadband amplifier a1, and a first capacitor C1 is connected in parallel with the first resistor R1. Specifically, the first resistor R1 and the second resistor R2 of the first feedback circuit are used for adjusting the static operating point of the first broadband amplifier a1, so that the first broadband amplifier a1 operates in an amplifying state; the first capacitor C1 is used to adjust the gain slope, so that the gain in the low frequency band is low and the gain in the high frequency band is high, and certainly, in order to ensure the gain flatness of the wideband signal, the gain slope of the gain compression circuit and the gain slope of the gain compensation circuit are opposite. More specifically, the value range of the first capacitor C1 is 20-200pF, as a preferred embodiment, the first capacitor C1 is 100pF, the first resistor R1 is 50 Ω, and the second resistor R2 is 120 Ω, and accordingly, the gain of the high-frequency band 3G frequency point in the gain compensation circuit is improved by about 4.5dB compared with the gain of the 0.5G frequency point.

It should be further noted that when determining the gain slope of the gain compensation circuit and the gain compression circuit, the gain slope depends on the improvement amount required by the high-frequency band noise floor, and the larger the slope, the larger the noise floor improvement amount. However, the large slope indicates that the compression amount of the high-band gain is large, and the excessive compression amount affects the power linearity (P-1dB) index of the system output. The margin of the original system power linearity (P-1dB) is set as P, the high-frequency band bottom noise improvement amount is set as S, the available high-frequency band gain compression amount or compensation amount is set as G, and the three index units are dB. If P is larger than or equal to S, determining that G is S; if P is less than or equal to S, G is P.

Further, as shown in fig. 2, the second feedback circuit includes a third resistor R3, a fourth resistor R4, and a third capacitor C3. Specifically, one end of a third resistor R3 is connected to the input end of the second broadband amplifier a2, the other end of the third resistor R3 is connected to the output end of the second broadband amplifier a2, and a fourth resistor R4 is connected in series with the third capacitor C3 and then connected in parallel with the third resistor R3, that is, one end of the fourth resistor R4 is connected to the input end of the second broadband amplifier a2, and one end of the third resistor R3 is connected to the output end of the second broadband amplifier a 2. Specifically, the third resistor R3 in the second feedback circuit is used to adjust the quiescent operating point of the second wideband amplifier a2, so that the second wideband amplifier a2 operates in the amplification state, and at the same time, the third resistor R3 is also used to adjust the full-band average gain; the fourth resistor R4 is connected in series with the third capacitor C3 for adjusting the gain slope, and the fourth resistor R4 is used for reducing the Q value, so that the signal can be ensured to be in a state of enabling the low-frequency gain to be high and enabling the high-frequency gain to be linearly reduced after passing through the gain compression circuit. More specifically, the value range of the third capacitor C3 is 5pF-20pF, and the value range of the fourth resistor R4 is 100-1000 Ω. As a preferred embodiment, the third resistor R3 is 2k Ω, the fourth resistor R4 is 510 Ω, and the third capacitor C3 is 10pF, and accordingly, the gain of the high-frequency band 3G frequency point in the gain compression circuit is reduced by about 4.5dB compared with the gain of the 0.5G frequency point.

As an option, the gain compression circuit further includes a first temperature-compensated attenuator TA1 and a fourth grounded capacitor C4, the fourth grounded capacitor C4 is connected to the output end of the second broadband amplifier a2, the first temperature-compensated attenuator TA1 is cascaded behind the fourth grounded capacitor C4, that is, the first end of the fourth grounded capacitor C4 is connected to the output end of the second broadband amplifier a2, the second end of the fourth grounded capacitor C4 is grounded, and the first end of the fourth grounded capacitor C4 is connected to the first temperature-compensated attenuator TA 1. Specifically, the fourth grounded capacitor C4 is used to achieve fine tuning of the gain slope; because the gain of the broadband amplifier changes with the temperature and directly affects the magnitude of the output noise floor, the first temperature-compensated attenuator TA1 can effectively compensate the noise floor fluctuation caused by high and low temperatures and improve the performance of the system gain at high and low temperatures. More specifically, the value range of the fourth ground capacitance is 0.3pF-1pF, as a preferred embodiment, the fourth ground capacitance is specifically 0.5pF, and the model of the first temperature-compensated attenuator TA1 is specifically TCA0604N 9.

Further, as shown in fig. 3, the transmitting end of the system further includes a laser connected to the output end of the gain compensation circuit, the receiving end further includes a photodetector and a low noise amplifier connected in sequence, the output end of the low noise amplifier is connected to the gain compression circuit, and the transmitting end is connected to the receiving end via an optical cable.

As an option, the output end of the gain compensation circuit is further connected with a second capacitor C2 for isolating direct current and direct current, and the output end of the first broadband amplifier a1 is connected with the laser through the second capacitor C2, so as to protect the static operating point of the laser. In one embodiment, the second capacitor C2 is 100 pF.

The embodiment 1 of the invention realizes the optimization of the background noise of the analog signal transmission system from 0.5G to 3G, the background noise of 0.5GHz is about-136 dBm/Hz, the background noise of 2GHz is about-134 dBm/Hz, and the background noise of 3GHz is about-132 dBm/Hz in the original non-optimized analog signal transmission system, and after the low-noise optimization is carried out by the gain compensation circuit and the gain compression circuit of the system, the background noise of 0.5GHz-3GHz is-136 +/-0.5 dBm/Hz, and the signal flatness is small.

The receiving end of the invention linearly reduces the gain of the high frequency band, namely the higher the frequency is, the lower the gain is, the higher the frequency is, the higher the noise is, the characteristic of the receiving end is just balanced with the characteristic that the higher the frequency is, the higher the noise is, therefore, the output noise of the high frequency band is reduced compared with the original fiber link, and the circuit can adjust the noise to be consistent with the low frequency band. The transmitting end is used for compensating the gain reduced by the high-frequency section of the receiving end, although the gain of the high-frequency section is relatively improved, the influence of the gain on the output background noise can be ignored, because the compensated gain is in front of the laser, according to the noise cascade principle, the positive gain is increased at the front stage of the system, which is beneficial to improving the system noise, and because the attenuation noise of the laser is extremely large, the influence of the laser on the background noise is far greater than that of the front stage, on the basis, the signal flatness of the whole system is small, and the communication quality is ensured.

Example 2

The present embodiment provides an optimization system for receiving bottom noise in an optical fiber transmission link, which solves the problem that in the prior art, the optimization cannot be performed for receiving low noise in a high frequency band in the optical fiber transmission link, and the system has the same inventive concept as that in embodiment 1, the system includes a transmitting end and a receiving end, the transmitting end includes a gain compensation circuit for compensating for a signal high frequency band gain, even if the low frequency band gain is low and the high frequency band gain is high, the receiving end includes a gain compression circuit for compressing the signal high frequency band gain, even if the low frequency band gain is high and the high frequency band gain is linearly reduced, the output bottom noise in the high frequency band is reduced compared with the original optical fiber link, the full frequency band low noise shows a flat trend, the gain flatness is ensured, the system signal flatness is small, the signal-to-noise ratio is high, and the communication quality is ensured.

Specifically, as shown in fig. 4, the gain compensation circuit includes a third wideband amplifier a11, a gain equalizer E1, a first attenuator AT1, and a dc block B1, which are connected in sequence, so that the adjustment process of the feedback circuit, which is difficult for the gain compensation circuit in embodiment 1, can be omitted; as shown in fig. 5, the gain compression circuit includes a fourth broadband amplifier a22, a second attenuator AT2, and a second temperature-dependent attenuator TA2 connected in sequence. Specifically, the first broadband amplifier a11 is used to provide compensation gain, the gain equalizer E1 attenuates the low frequency band greatly and attenuates the high frequency band less to ensure gain compensation of the high frequency band of the signal, the first attenuator AT1 is specifically a resistive attenuator which is used to make the gain compensation circuit present a good impedance matching circuit, and the B1 dc-blocking device is used to protect the quiescent operating point of the laser; the fourth broadband amplifier a22 in the gain compression circuit is used for amplifying signals, so that the whole gain compression circuit presents a frequency response characteristic that the gain AT the low frequency end is high and the gain AT the high frequency end is linearly reduced, the second attenuator AT2 is specifically a resistive attenuator and is used for presenting a good impedance matching circuit to the gain compression circuit, and the second temperature-compensated attenuator TA2 is used for compensating the noise fluctuation caused by high and low temperatures and improving the performance of the high and low temperatures of the system gain.

As an option, in an actual application scenario, the fourth wideband amplifier a22 has no suitable amplifier model, and does not achieve an ideal signal amplification effect, the fourth wideband amplifier a22 may be split into a combination form in which an amplifier with a flat full-band response is connected in series with a low-pass filter, that is, the fourth wideband amplifier a22 includes an amplifier with a flat full-band response and a low-pass filter which are connected in sequence, and the frequency response of the filter is adjusted to make the entire gain compression circuit exhibit a frequency response characteristic in which the gain at the low frequency end is higher and the gain at the high frequency end is linearly reduced.

Example 3

The present embodiment provides an optimization method for receiving background noise in an optical fiber transmission link, which is the same as the inventive concept in embodiment 1, and the method includes:

the gain compensation circuit is arranged at the transmitting end, the gain compression circuit is arranged at the receiving end, the gain compensation circuit compensates the gain of the signal high frequency band, and the gain compression circuit compresses the gain of the signal high frequency band, so that the output bottom noise of the high frequency band is reduced compared with the original optical fiber link, the signal flatness of the system is small, the signal-to-noise ratio is high, and the communication quality is guaranteed.

Further, the gain compensation circuit is specifically the gain compensation circuit in embodiment 1, and the gain compression circuit is specifically the gain compression circuit in embodiment 1, and the value of the first capacitor C1 in the first feedback circuit, the value of the fourth resistor R4 in the second feedback circuit, and the value of the third capacitor C3 in the second feedback circuit are changed, so that the gain slope of the gain compensation circuit and the gain slope of the gain compensation circuit are opposite numbers, so as to ensure the gain flatness of the broadband signal, and ensure the communication quality of the system. As a preferred embodiment, the first capacitor C1 is specifically 100pF, the fourth resistor R4 is 510 Ω, and the third capacitor C3 is 10pF, and accordingly, the gain of the high-frequency band 3G frequency point in the gain compensation circuit is increased by about 4.5dB compared with the gain of the 0.5G frequency point, and the gain of the high-frequency band 3G frequency point in the gain compression circuit is decreased by about 4.5dB compared with the gain of the 0.5G frequency point.

Further, the value of the fourth ground capacitor C4 in the second feedback circuit is adjusted to fine tune the slope of the gain compression circuit. As a preferred embodiment, the fourth ground capacitor C4 is 0.5 pF.

The above detailed description is for the purpose of describing the invention in detail, and it should not be construed that the detailed description is limited to the description, and it will be apparent to those skilled in the art that various modifications and substitutions can be made without departing from the spirit of the invention.