阅读说明：本技术 信号发送装置和信号发送方法 (Signal transmission device and signal transmission method ) 是由 吴自强 陈卓 黄嘉琦 张深茂 敖学渊 王忠忠 杨奇 于 2019-09-30 设计创作，主要内容包括：提供了一种信号发送装置和信号发送方法。所述信号发送装置包括：信号生成器,被配置为生成传输信号、第一载波以及与第一载波相位相差90度的第二载波,其中,第一载波与第二载波均为基于delta-sigma调制生成的信号；IQ调制器,被配置为基于传输信号与第一载波进行IQ调制以生成第一发送信号,以及基于所述传输信号与第二载波进行IQ调制以生成第二发送信号；以及发射器,被配置为在第一时隙发送所述第一发送信号,并在第二时隙发送所述第二发送信号。上述信号发送装置可以具有简单的结构,并且通过上述信号发送装置和信号发送方法,能够在接收端采用直接检测的方法恢复信号,使接收端具有更简单的结构。(A signal transmission apparatus and a signal transmission method are provided. The signal transmission device includes: a signal generator configured to generate a transmission signal, a first carrier, and a second carrier that is 90 degrees out of phase with the first carrier, wherein the first carrier and the second carrier are both signals generated based on delta-sigma modulation; an IQ modulator configured to perform IQ modulation with a first carrier based on a transmission signal to generate a first transmission signal, and to perform IQ modulation with a second carrier based on the transmission signal to generate a second transmission signal; and a transmitter configured to transmit the first transmission signal in a first time slot and transmit the second transmission signal in a second time slot. The signal transmitting apparatus may have a simple configuration, and the signal transmitting apparatus and the signal transmitting method may recover a signal at a receiving end by using a direct detection method, so that the receiving end has a simpler configuration.)

1. A signal transmission apparatus comprising:

a signal generator configured to generate a transmission signal, a first carrier, and a second carrier that is 90 degrees out of phase with the first carrier, wherein the first carrier and the second carrier are both signals generated based on delta-sigma modulation;

an IQ modulator configured to perform IQ modulation with a first carrier based on a transmission signal to generate a first transmission signal, and to perform IQ modulation with a second carrier based on the transmission signal to generate a second transmission signal; and

a transmitter configured to transmit the first transmission signal in a first time slot and transmit the second transmission signal in a second time slot.

2. The signal transmission apparatus of claim 1, wherein each of the first carrier and the second carrier includes a sine signal portion and a cosine signal portion,

and wherein the signal generator comprises:

a digital input/output interface configured to receive a first digital signal corresponding to a cosine signal and a second digital signal corresponding to a sine signal generated based on delta-sigma modulation; and

a low pass filter configured to low pass filter the first and second digital signals, respectively, to generate the cosine signal portion and the sine signal portion to generate the first and second carriers.

3. The signal transmission apparatus of claim 2, wherein the first and second digital signals are generated by simulation.

4. The signal transmission apparatus according to claim 2 or 3, wherein the transmission signal includes a first transmission signal and a second transmission signal, and wherein the first digital signal and the second digital signal are N bits, the first transmission signal and the second transmission signal are N bits, where N is an integer greater than or equal to 1.

5. The signal transmission apparatus of claim 4, wherein the signal generator further comprises an attenuator for attenuating the first transmission signal and the second transmission signal.

6. The signal transmission apparatus according to claim 4, further comprising:

a combiner configured to combine the first and second transmission signals with cosine and sine signal portions of a first carrier, respectively, to generate first and second combined signals, and to combine the first and second transmission signals with sine and cosine signal portions of a second carrier, respectively, to generate third and fourth combined signals;

wherein the IQ modulator is configured to IQ modulate the first and second combined signals to generate a first transmit signal, and IQ modulate the third and fourth combined signals to generate a second transmit signal.

7. A method of signaling, comprising:

generating a transmission signal and a first carrier, wherein the first carrier is a signal generated based on delta-sigma modulation,

performing IQ modulation on the transmission signal and a first carrier to generate a first transmission signal, and transmitting the first transmission signal at a first time slot;

generating a second carrier 90 degrees out of phase with said first carrier, wherein the second carrier is a signal generated based on delta-sigma modulation,

IQ-modulating the transmission signal with a second carrier to generate a second transmission signal, and transmitting the second transmission signal in a second time slot.

8. The signal transmission method of claim 7, wherein each of the first carrier and the second carrier comprises a sine signal portion and a cosine signal portion, and wherein,

generating the first carrier or the second carrier includes:

receiving a first digital signal corresponding to a cosine signal and a second digital signal corresponding to a sine signal generated based on delta-sigma modulation, an

Low pass filtering the first and second digital signals, respectively, to generate the cosine signal portion and the sine signal portion to generate the first or second carrier.

9. The signal transmission method according to claim 8, wherein the first and second digital signals are generated by simulation.

10. The signal transmission method according to claim 8 or 9, wherein the transmission signal includes a first transmission signal and a second transmission signal, and wherein the first digital signal and the second digital signal are N bits, and the first transmission signal and the second transmission signal are N bits, where N is an integer greater than or equal to 1.

11. The signal transmission method of claim 10, wherein the generating a transmission signal further comprises:

the first transmission signal and the second transmission signal are attenuated.

12. The signal transmission method of claim 10, further comprising:

combining the first transmission signal and the second transmission signal with a cosine signal part and a sine signal part of the first carrier, respectively, to generate a first combined signal and a second combined signal, an

Combining the first transmission signal and the second transmission signal with a sine signal part and a cosine signal part of a second carrier, respectively, to generate a third combined signal and a fourth combined signal;

wherein performing IQ modulation based on the transmission signal and the first carrier to generate a first transmission signal comprises: IQ modulating the first combined signal and the second combined signal to generate a first transmit signal; and wherein the step of (a) is,

performing IQ modulation on the transmission signal and a second carrier to generate a second transmission signal includes: the third sum signal and the fourth combined signal are IQ modulated to generate a second transmission signal.

Technical Field

The present invention relates to the field of optical communications, and in particular to a signal transmission apparatus and a signal transmission method for use in an optical communication system, and a corresponding signal reception apparatus and a signal reception method.

Technical Field

In the field of optical communications, with the rapidly growing demand for metro and data center services, there is a need to implement low cost high performance coherent and non-coherent systems with data rates greater than 100Gb/s and transmission distances greater than 100 km. Considering Digital Signal Processing (DSP), power consumption and cost together, a direct detection scheme using a single wavelength and a single Photodetector (PD) is proposed. However, fading caused by dispersion causes signals with a rate of over 25Gb/s to be difficult to transmit over 80 km. To achieve medium and long distance transmission, various self-coherent detection techniques are proposed to detect complex signals in a direct detection manner. However, in these techniques, it is often necessary to employ high speed digital-to-analog converters or optical frequency shifters, which can add significant cost and complexity to the system.

Disclosure of Invention

The present invention has been made in view of the above problems. An object of the present invention is to provide a signal transmission apparatus and a signal transmission method.

According to an aspect of the present disclosure, there is provided a signal transmission apparatus including: a signal generator configured to generate a transmission signal, a first carrier, and a second carrier that is 90 degrees out of phase with the first carrier, wherein the first carrier and the second carrier are both signals generated based on delta-sigma modulation; an IQ modulator configured to perform IQ modulation with a first carrier based on a transmission signal to generate a first transmission signal, and to perform IQ modulation with a second carrier based on the transmission signal to generate a second transmission signal; and a transmitter configured to transmit the first transmission signal in a first time slot and transmit the second transmission signal in a second time slot.

According to another aspect of the present disclosure, there is provided a signal transmission method including: generating a transmission signal and a first carrier, wherein the first carrier is a signal generated based on delta-sigma modulation, performing IQ modulation based on the transmission signal and the first carrier to generate a first transmission signal, and transmitting the first transmission signal at a first time slot; generating a second carrier which is a signal generated based on delta-sigma modulation and is 90 degrees out of phase with the first carrier, performing IQ modulation based on the transmission signal and the second carrier to generate a second transmission signal, and transmitting the second transmission signal in a second time slot.

In the signal transmitting apparatus and the signal transmitting method according to the above aspects of the present invention, the same transmission signal is combined and transmitted with the carrier signal having a phase difference of 90 degrees generated based on the delta-sigma modulation principle in two adjacent time slots, respectively, so that the structure of the signal transmitting apparatus can be simplified, and the original transmission signal can be recovered at the receiving end simply by a direct detection method, thereby reducing the complexity of the receiving end.

Drawings

The above and other objects, features, and advantages of the present invention will become more apparent by describing in detail embodiments thereof with reference to the attached drawings in which:

fig. 1(a) shows a schematic diagram of a signal resulting from oversampling and noise shaping a sine signal or a cosine signal.

Fig. 1(b) shows a schematic diagram of the signal resulting after low pass filtering the signal shown in fig. 1 (a).

Fig. 1(c) shows a schematic diagram of a sampling waveform of the delta-sigma bitstream.

Fig. 1(d) shows a schematic diagram of a sinusoidal signal resulting from low-pass filtering the delta-sigma bitstream shown in fig. 1 (c).

Fig. 2 shows a schematic diagram of a block-wise phase switching (block-wise phase switching) transmission technique.

Fig. 3 shows a block diagram of a signal transmission apparatus according to an embodiment of the present invention.

Fig. 4 is an exemplary manner of the signal generator 110 according to the signal transmission apparatus shown in fig. 3.

Fig. 5 is a diagram schematically showing an example implementation of a signal transmission apparatus according to an embodiment of the present invention.

Fig. 6 shows a block diagram of a signal receiving apparatus for receiving an optical signal transmitted by the signal transmitting apparatus.

Fig. 7 shows a flowchart of a signal transmission method according to an embodiment of the present invention.

Fig. 8 shows a flowchart of a signal receiving method for receiving an optical signal transmitted according to the signal transmitting method shown in fig. 7.

Detailed Description

Embodiments of the present disclosure will be described in detail so that those skilled in the art can easily perform them with reference to the following drawings. However, one or more embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. For clarity, portions that are not relevant to the description will be omitted.

The terms used in the present specification are those general terms currently widely used in the art in consideration of functions related to the present disclosure, but they may be changed according to the intention of a person having ordinary skill in the art, precedent, or new technology in the art. Also, specific terms may be selected by the applicant, and in this case, their detailed meanings will be described in the detailed description of the present disclosure. Therefore, the terms used in the specification should not be construed as simple names but based on the meanings of the terms and the overall description of the present disclosure.

In the embodiment of the invention, the delta-sigma modulation and the block-by-block phase switching (block-by-block phase switching) transmission technology are combined, so that the device structures of a transmitting end and a receiving end can be simplified, and the complexity of the whole communication system is reduced.

First, the principle of the delta-sigma modulation technique is briefly described.

delta-sigma modulation is a technique that can modulate an analog signal using one quantization bit, which includes oversampling analog-to-digital conversion, noise shaping, and low-pass filtering. By this technique, an analog sine signal or an analog cosine signal can be converted into a data stream of one bit.

Specifically, in delta-sigma modulation, the sine signal or the cosine signal is first oversampled. Nyquist sampling limited by the number of quantization bits generates quantization noise in the nyquist zone. By oversampling, the nyquist zone can be extended and the quantization noise extended to a larger range. The oversampled signal is then noise shaped to transfer the quantization noise energy from the low frequency end to the high frequency end, which will significantly reduce the low frequency noise. Fig. 1(a) shows a schematic diagram of a signal resulting from oversampling and noise shaping a sine signal or a cosine signal. The noise-shaped signal is then filtered using a low-pass filter to filter out high-frequency noise, thereby producing a digital signal stream quantized using one bit. Fig. 1(b) shows a schematic diagram of the signal resulting after low pass filtering the signal shown in fig. 1 (a). Thus, delta-sigma modulation corresponds to analog-to-digital conversion, which can convert an analog signal to a digital signal stream output at a sample rate. It should be noted that although the delta-sigma modulation is described above by taking one bit as an example, this is not restrictive, and the signal may be quantized by a plurality of bits to generate a digital signal stream of a plurality of bits.

The digital signal stream generated by delta-sigma modulation can be restored to the original analog sine signal or cosine signal by passing through a low-pass filter. Fig. 1(c) shows a schematic diagram of a sampling waveform of the delta-sigma bitstream, and fig. 1(d) shows a schematic diagram of a sine signal and a cosine signal generated by low-pass filtering the delta-sigma bitstream shown in fig. 1 (c).

In the embodiment of the patent, this property is utilized to generate sine signals and cosine signals through delta-sigma modulation instead of generating the sine signals and the cosine signals through a digital-to-analog converter in the traditional way. Specifically, because delta-sigma modulation can be performed using computer simulation, a digital signal stream can be generated based on delta-sigma modulation in a simulation manner. Then, the digital signal stream is received through a high-speed digital input/output (I/O) interface and converted into an analog signal through a low-pass filter, thereby eliminating the need for a digital-to-analog converter, i.e., equivalent to replacing the originally required digital-to-analog converter with a low-pass filter, whereby the structure of the transmitting apparatus can be simplified.

Next, the principle of a block-wise phase switching (block-wise phase switching) transmission technique is described.

In the block-by-block phase switching transmission technique, signals are transmitted in time slots, and the signal transmitted per time slot is referred to as one "block". The signal of each "block" consists of two parts, one being the transmission signal and one being the carrier wave. The transmission signals of two consecutive blocks are identical but the carriers of the two blocks have a phase difference of 90, i.e. the phase is switched between the carriers of two consecutive blocks, as shown in fig. 2. Here, the "carrier wave" may also be referred to as a "virtual carrier wave" which is a signal combined with a transmission signal before the transmission signal is actually modulated and transmitted. In the present invention, 90 degree phase switching of the carrier can be easily achieved by the delta-sigma modulation principle.

Take QPSK signal as an example. The transmission signal of the "block" transmitted in the first time slot can be expressed as

E_S＝E_I+j×E_Q，

Wherein E is_SRepresents the transmission signal, E_IAnd E_QRespectively representing the I component (which may also be referred to as the first transmission signal) and the Q component (which may also be referred to as the second transmission signal) of the transmission signal. The carrier of this "block" may be denoted as E_c＝A(cosωt+j×sinωt)，

Wherein E is_cRepresenting the carrier wave, ω is the frequency of the carrier wave and a is the amplitude of the carrier wave, and therefore the carrier wave comprises two parts, namely a cosine signal part Acos ω t and a sine signal part Asin ω t.

By using the block-by-block phase switching transmission technique at the transmitting end, the structure and operation of the receiving end can be simplified. Specifically, at the receiving end, the current I obtained by detecting the received optical signal₁Watch capable of showingShown as follows:

I₁＝|E_c+E_s|²＝E_I ²+E_Q ²+A²+2E_IAcosωt+2E_QAsinωt，

for QPSK signals, E_I ²+E_Q ²Is a constant quantity, so E_I ²+E_Q ²+A²Can be simply filtered off, so that can be obtained

I₁'＝2E_IAcosωt+2E_QAsinωt

The transmission signal of the "block" transmitted at the 2 nd slot may be expressed as

E_S＝E_I+j×E_Q，

Which is identical to the transmission signal of the "block" transmitted at the 1 st slot. The carrier of the "block" transmitted in the 2 nd slot may be denoted as E_c'＝j×E_c＝A(-sinωt+j×cosωt)

Which is 90 degrees different from the carrier of the "block" transmitted in the 1 st slot. The carrier wave comprises two parts, a sine signal part-Asin ω t and a cosine signal part Acos ω t.

For the second time slot, in the case of a QPSK signal, at the receiving end, the current I obtained by detecting the received optical signal is obtained₂Can be expressed as:

I₂＝|j×E_c+E_s|²＝E_I ²+E_Q ²+A²+2E_QAcosωt-2E_IAsinωt，

thus, the current with constant filtered can be obtained

I₂'＝2E_QAcosωt-2E_IAsinωt

From I₁' and I₂' it can be calculated:

that is, the original signal can be recovered.

For the conventional QPSK signal, coherent demodulation is used to recover the signal, and by using the block-by-block phase-switching transmission technique, the original signal can be recovered by direct detection. Greatly simplifying the complexity of the receiving end and reducing the cost of the receiver.

Hereinafter, a signal transmission apparatus according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

Fig. 3 is a block diagram illustrating a signal transmission apparatus according to an exemplary embodiment of the present invention.

Referring to fig. 3, the signal transmission apparatus 100 according to the exemplary embodiment of the present invention includes a signal generator 110, an IQ modulator 120, and a transmitter 130.

The signal generator 110 is configured to generate a transmission signal, a first carrier, and a second carrier that is 90 degrees out of phase with the first carrier, wherein the first carrier and the second carrier are both signals generated based on delta-sigma modulation.

The transmission signal is a signal, such as a digital signal, to be transmitted to a receiving end. The transmission signal may include a first transmission signal of N bits (N is an integer greater than or equal to 1) and a second transmission signal of N bits. As described above, the transmission signal may be a complex signal, wherein the first transmission signal may be an I component of the transmission signal and the second transmission signal may be a Q component of the transmission signal.

The transmission signal may be generated in a variety of implementations. In one implementation, the signal generator may include a digital I/O interface for receiving the transmission signal from the outside, as shown in fig. 4. For example, the signal generator may include two digital I/O interfaces for receiving the first transmission signal and the second transmission signal from the outside, respectively. Optionally, the digital I/O interface is a high speed digital I/O interface adapted to the rate of the transmission signal. In another implementation, the signal generator may directly generate the transmission signal. Optionally, as shown in fig. 4, the signal generator may further include an Attenuator (ATT) for attenuating the transmission signal to achieve a better carrier signal power ratio.

The first carrier may be a carrier of a signal block transmitted in the first time slot as described above, and the second carrier may be a carrier of a signal block transmitted in the second time slot as described above. The first time slot and the second time slot may be two consecutive time slots or two adjacent time slots. It should be noted that the time slots are merely examples, and the time unit for transmitting the signal may be other time units besides the time slots.

As described above, each of the first carrier and the second carrier includes a sine signal portion and a cosine signal portion. In one implementation, the signal generator may include an additional digital I/O interface, and a Low Pass Filter (LPF), as shown in fig. 4. The digital I/O interface is used for receiving a first digital signal corresponding to a cosine signal and a second digital signal corresponding to a sine signal which are generated based on delta-sigma modulation. Optionally, the digital I/O interface is a high speed digital I/O interface adapted to the rate of the first and second digital signals. The first and second digital signals may be generated based on delta-sigma modulation by simulation. The simulation may be performed by a computing device provided outside the signal transmission device. Alternatively, the computing means may be located within the signaling means, for example within a digital I/O interface.

In particular, for the simulation, a cosine signal may be generated by the calculation means, and then a digital signal corresponding to the cosine signal, i.e. said first digital signal, is generated by delta-sigma modulating the cosine signal in the manner described above. Likewise, a sinusoidal signal may be generated by the calculation means, and then a digital signal corresponding to this sinusoidal signal, i.e. said second digital signal, is generated by delta-sigma modulating the sinusoidal signal in the manner described above. The first digital signal and the second digital signal are then received into a signal transmitting device via the digital I/O interface, e.g., two digital I/O interfaces. Then, the first digital signal may be low-pass filtered using the low-pass filter to generate a cosine signal as the cosine signal portion, and the second digital signal may be low-pass filtered using the low-pass filter to generate a sine signal as the sine signal portion. Thus, a first carrier to be transmitted in a first time slot and a second carrier to be transmitted in a second time slot may be generated in accordance with Ec and Ec' described above.

Returning to fig. 3, the IQ modulator 120 is configured to IQ modulate a transmission signal with a first carrier to generate a first transmission signal, and IQ modulate the transmission signal with a second carrier to generate a second transmission signal.

As an example, the signal transmitting apparatus further includes a combiner 140, as shown in fig. 3, configured to provide the IQ modulator 120 with a signal to be modulated generated based on the transmission signal and the first carrier, and a signal to be modulated generated based on the transmission signal and the second carrier. The combiner 140 may be, for example, an adder. Specifically, for the first time slot, the combiner 140 combines (e.g., adds) the first transmission signal with the cosine signal portion of the first carrier to generate a first combined signal, and combines (e.g., adds) the second transmission signal with the sine signal portion of the first carrier to generate a second combined signal. The first combined signal and the second combined signal are signals to be modulated. Similarly, for the second time slot, the combiner 140 combines (e.g., subtracts) the first transmission signal from the sinusoidal signal portion of the second carrier to generate a third combined signal, and combines (e.g., adds) the second transmission signal to the cosine signal portion of the second carrier to generate a fourth combined signal. The third combined signal and the fourth combined signal are signals to be modulated.

As another example, the combiner 140 may be located inside the IQ modulator 120, and when the modulator 120 receives the transmission signal and the first carrier or the second carrier, the combiner 140 may be utilized to generate the first combined signal and the second combined signal to be modulated based on the transmission signal and the first carrier, and generate the third combined signal and the fourth combined signal to be modulated based on the transmission signal and the second carrier in the manner described above.

Then, the IQ modulator 120 may IQ modulate the first combined signal and the second combined signal to generate a first transmit signal for transmission at the first time slot, and IQ modulate the third combined signal and the fourth combined signal to generate a second transmit signal for transmission at the second time slot.

With continued reference to fig. 3, the transmitter 130 transmits a first transmission signal in a first time slot and a second transmission signal in a second time slot. Optionally, the optical signal may also be amplified by an optical amplifier before being transmitted.

The signal transmission apparatus shown in fig. 3 may have various implementations, and one example implementation of the signal transmission apparatus will be described below.

Fig. 5 is a diagram schematically showing an example implementation of a signal transmission apparatus according to an embodiment of the present invention.

Referring to fig. 5, the signal transmission apparatus 100 according to the exemplary embodiment of the present invention includes a signal generator 110, an IQ modulator 120, and a transmitter 130.

The signal generator 110 includes four I/O interfaces 1-4, which transmit digital signals of N bits. Taking the first time slot as an example, I/O interfaces 1 and 3 respectively transmit the first transmission signal dataI and the second transmission signal dataQ described above, and I/O interfaces 2 and 4 respectively transmit the first digital signal toneI and the second digital signal toneQ described above. The first transmission signal dataI and the second transmission signal dataQ may first be passed through the attenuator ATT, respectively, to obtain a better case carrier to signal power ratio. The first digital signal toneI and the second digital signal toneQ are passed through a low pass filter LPF to generate a cosine signal portion and a sine signal portion of the first carrier as described above, thereby generating a first carrier signal. Next, the combiner 140 combines (e.g., adds) the first transmission signal dataI and the cosine signal portion of the first carrier signal to generate a first combined signal as described above, and combines (e.g., adds) the second transmission signal dataQ and the sine signal portion of the first carrier signal to generate a second combined signal as described above, and the first and second combined signals are IQ-modulated by an IQ modulator to generate a first transmission signal and transmitted by the transmitter. The first transmission signal may also be amplified by an optical amplifier OA before it is transmitted. Similarly, for a second time slot, I/O interfaces 1 and 3 transmit said first transmission signal dataI and said second transmission signal dataQ, respectively, and I/O interfaces 2 and 4 transmit said first digital signal toneI and said second digital signal toneQ, respectively. The first transmission signal dataI and the second transmission signal dataQ may be first attenuated by the attenuator ATT, respectively. The first digital signal toneI and the second digital signal toneQ are passed through a low pass filter LPF to generate the cosine signal part and the sine signal part of the second carrier as described above, thereby generating a second carrier signal. Next, the combiner 140 combines (e.g., subtracts) the first transmission signal dataI and the sine signal part of the second carrier to generate said third combined signal, and combines (e.g., adds) the second transmission signal dataQ and the cosine signal part of the second carrier to generate the fourth combined signal described above, and finally the third and fourth combined signals are modulated by the IQ modulator to generate a second transmission signal and transmitted by the transmitter. The second transmission signal may also be amplified by an optical amplifier OA before it is transmitted.

The optical signal reaches a signal receiving device through an optical fiber, and the signal receiving device processes the optical signal and recovers a transmission signal sent by a sending end.

Next, a signal receiving apparatus according to an embodiment of the present invention will be described.

Fig. 6 is a block diagram of a signal receiving apparatus 600 for receiving an optical signal transmitted by the signal transmitting apparatus. As shown in fig. 6, the signal receiving apparatus 600 includes a detector 610 and a processor 620.

The detector 610 is used to detect the received optical signal to convert it into a current. For example, the detector610 may be a Photodiode (PD). As described above, for the first time slot, the current detected by the detector 610 can be represented as I described above₁＝|E_c+E_s|²＝E_I ²+E_Q ²+A²+2E_IAcosωt+2E_QAsin ω t, the signal detected by the detector 610 may be represented as I as described above for the second time slot₂＝|j×E_c+E_s|²＝E_I ²+E_Q ²+A²+2E_QAcosωt-2E_IAsin ω t. Here, the detector 610 may be a PD having an ac coupling function that detects the current I₁And I₂Then its DC component is filtered out to output I 'as described above'₁And l'₂. Alternatively, the detector 610 may output the current I directly₁And I₂And in a subsequent step its dc component is filtered out by processor 620 to produce I 'as described above'₁And l'₂。

The processor 620 processes the output signal of the detector 610 in two time slots to recover the digital signal transmitted at the transmitting end. The processor may be, for example, a Digital Signal Processor (DSP). Specifically, the signal I 'from which the DC component is filtered out is used'₁And l'₂The processor 620 may calculateAndthat is, the first transmission signal and the second transmission signal described above can be obtained. It should be noted that the processing performed by the DSP may further include synchronization, complex signal reconstruction, dispersion compensation, CMA, residual phase compensation, and constellation construction and decision, which are not described herein again.

For the traditional QPSK signal, a coherent demodulation mode needs to be used to recover the signal, but the system according to the embodiment of the present invention only needs to directly detect the signal by a single PD and then recover the original signal by DSP processing, which greatly reduces the complexity of the receiving end.

A signal transmission method according to an embodiment of the present invention is described below. Fig. 7 is a flowchart illustrating a signal transmission method according to an embodiment of the present invention. The method may be performed by the signaling device described in fig. 3 or fig. 5. Since various details of the method have been mentioned in describing the signal transmission apparatus according to the embodiment of the present invention, only the method will be briefly described herein.

Referring to fig. 7, at step S710, a transmission signal and a first carrier are generated, wherein the first carrier is a signal generated based on delta-sigma modulation. Here, the transmission signal includes a first transmission signal of N bits and a second transmission signal of N bits, and as described above, the first carrier includes sine signal and cosine signal portions. Generating the first carrier includes receiving a first digital signal corresponding to a cosine signal and a second digital signal corresponding to a sine signal generated based on delta-sigma modulation, and low-pass filtering the first digital signal and the second digital signal, respectively, to generate the cosine signal portion and the sine signal portion, thereby generating the first carrier.

With continued reference to fig. 7, at step S720, IQ modulation is performed based on the transmission signal and the first carrier to generate a first transmission signal, and then the first transmission signal is transmitted at the first time slot. Specifically, a first transmission signal and a second transmission signal are combined with a cosine signal part and a sine signal part of a first carrier, respectively, to generate a first combined signal and a second combined signal, and then the first combined signal and the second combined signal are IQ-modulated to generate a first transmission signal.

At step S730, a second carrier that is 90 degrees out of phase with the first carrier at S710 is generated. Here, as described above, the second carrier wave also includes a sine signal portion and a cosine signal portion. And the generation of the sine signal part and the cosine signal part is the same as step S710.

At step S740, IQ-modulating based on the transmission signal and the second carrier to generate a second transmission signal, and transmitting the second transmission signal in the second time slot. Here, the first transmission signal and the second transmission signal are combined with a sine signal part and a cosine signal part of the second carrier, respectively, to generate a third combined signal and a fourth combined signal, and then the third combined signal and the fourth combined signal are IQ-modulated to generate a second transmission signal.

Fig. 8 shows a flowchart of a signal receiving method for receiving an optical signal transmitted according to the signal transmitting method shown in fig. 7. The method may be performed by the receiving device described above.

Since the specific steps of the receiving end have been described in detail in the description of the receiving apparatus in fig. 6, they are briefly introduced here.

The received optical signal is detected to be converted into a current at step S810. Alternatively, since the signal is attenuated by the transmission process, the received optical signal may be amplified and then detected. As described above, for the first time slot, the detected current may be represented as I as described above₁For the second time slot, the detected current may be represented as I as described above₂. The current may then be filtered to remove a DC component, producing I 'as described above'₁And l'₂。

Next, at step S820, the two time-slot signals I 'obtained at step S810 are processed'₁And l'₂Processing is performed so as to recover the digital signals transmitted at the transmitting end, i.e., the first transmission signal and the second transmission signal described above. Specifically, in step S820, I 'may be passed according to the formula described above'₁And l'₂Can calculate E_IAnd E_QThereby obtaining the first transmission signal and the second transmission signal described above, thereby recovering the transmitted signals.

In contrast to conventional optical communication systems that require coherent demodulation to recover the signal, the method of the present invention, in which the original signal is recovered by using a block-by-block phase-switching transmission technique, requires only direct detection. Greatly simplifying the complexity of the receiving end and reducing the cost of the receiver. In addition, the delta-sigma modulation is used for generating sine signals and cosine signals, the traditional mode of generating sine signals and cosine signals through a digital-to-analog converter is replaced, the requirement for the digital-to-analog converter is eliminated, namely, the low-pass filter is used for replacing the originally required digital-to-analog converter, and therefore the structure of the transmitting device can be simplified.

Although the present invention has been described in the present embodiment with respect to the field of optical signal transmission, it should be understood that the present invention is not limited thereto, and is also applicable to the field of wireless communication in which signal transmission is performed using electromagnetic waves.

While example embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope and spirit of the invention as defined by the appended claims and their equivalents.