WO2011023083A1

WO2011023083A1 - Optical transmitter and method for generating optical signals

Info

Publication number: WO2011023083A1
Application number: PCT/CN2010/076228
Authority: WO
Inventors: 胡小锋; 张亮; 苏翼凯; 熊前进
Original assignee: 华为技术有限公司; 上海交通大学
Priority date: 2009-08-31
Filing date: 2010-08-23
Publication date: 2011-03-03
Also published as: CN101997608B; CN101997608A

Abstract

The present invention relates to the technical field of optical signal processing. In order to resolve the problems of great accumulative insertion loss and high cost, which are caused by the usage of multiple cascaded modulators in prior art, an optical transmitter and a method for generating optical signals are provided in the embodiments of the present invention, wherein the optical transmitter includes: an optical source, used for transmitting optical carrier; a dual-parallel Mach-Zender Modulator(MZM), used for receiving the first binary electrical signals and the second binary electrical signals, and modulating said optical carriers to obtain a quaternary optical signals according to the first and the second binary electrical signals; a dual-drive MZM, used for receiving the third binary electrical signals and the fourth binary electrical signals, and modulating said quaternary optical signals to obtain hexadecimal optical signals according to the third and the fourth binary electrical signals. The beneficial effect of the present invention is that less modulators are needed, the synchronization between the optical signals and electrical signals is easy, the insertion loss is low, and integration is easy.

Description

Optical transmitter and method for generating optical signal

This application claims priority to Chinese Patent Application No. 200910169691.7, entitled "A Method for Producing Optical Transmitters and Optical Signals", filed on August 31, 2009, the entire contents of which are incorporated by reference. In this application.

Technical field

The present invention relates to the field of communications, and more particularly to an optical transmitter and a method for generating an optical signal. Background technique

With the popularity of high-speed Ethernet and the booming of multimedia services, higher requirements have been placed on the communication capacity that can be supported by existing digital optical fiber communication systems based on Wavelength Division Multiplexing (WDM) technology. From an economic point of view, relying on the equipment and devices of the existing communication system, there are currently two options for improving the communication capacity of the WDM communication system: First, increase the symbol rate of the transmitted signal, such as 100 Gb/s. However, this solution has the great disadvantage of requiring high-speed optoelectronic devices, which are expensive and easily damaged at the current level of device fabrication. Another solution is to use a multi-ary modulation pattern without changing the symbol rate of the signal transmission, so that the bit rate of the binary pattern is obtained several times at the same symbol rate, and the communication capacity of the communication system is improved. Compared with the binary pattern, the multi-ary modulation pattern has a high spectrum utilization rate, and the frequency band occupied at the same bit rate is narrow, so it has a good resistance to Chromatic Dispersion (CD), polarization mode. Polarization Mode Dispersion (PMD) and the ability to nonlinear noise.

Researchers began research on multi-ary modulation patterns a few years ago, mainly quadrature phase shift keying.

(Quarature Phase-shift Keying, QPSK) signal. At present, research on various aspects of QPSK modulation patterns has been basically mature, and researchers have begun to test the performance of higher-order patterns, such as octal phase-shift keying signals (8PSK), hexadecimal quadrature amplitude modulation signals. ( 16 Quadrature Amplitude Modulation, 16QAM ). Each symbol of the 8PSK modulation pattern carries 3 bits, and each symbol of the 16QAM modulation pattern carries 4 bits of information, and their spectrum utilization ratio is improved and better than the QPSK pattern. Chromatic dispersion tolerance and polarization mode dispersion tolerance. 16QAM is mainly divided into three categories, namely Square- 16 Quadrature Amplitude Modulation (square- 16QAM), Star- 16 Quadrature Amplitude Modulation (Star- 16 Quadrature Amplitude Modulation, star-16QAM ) and sixteen 16 Amplitude Phase Modulation (16APSK). With the development of high-speed digital signal processing technology in recent years, the phase-light communication technology has recently attracted people's attention. Compared with the differential phase-demodulation technology, the phase-demodulation receiver has a simple structure and high system sensitivity. And can equalize and compensate the received signal on the electrical domain. As the modulation order increases, its advantages become more apparent.

Based on the coherent reception technology, designing a multi-format multi-level transmitter scheme has obvious practical significance for improving the capacity of the fiber-optic communication system.

In the prior art, a plurality of cascaded phase modulators (PM) and a Mach-Zender Modulator (MZM) are used to generate a star-16QAM optical signal, the implementation of which is shown in FIG. Using 3 cascaded phase modulators, an 8PSK signal is generated, then an MZM is used for intensity modulation, and the intensity modulated signal is controlled to generate the desired star-16QAM signal.

However, the above prior art has the following disadvantages: four modulators are required, the system structure is complicated, and the cost is high; the precise synchronization between the four modulator drive signals is required, and the adjustment is complicated; the cumulative insertion loss of the four modulators is large. The noise on the electrical signal is directly mapped to the phase of the optical signal, affecting the signal. Summary of the invention

The embodiment of the invention provides a method for generating an optical transmitter and an optical signal, which is used for solving the problem of large cumulative insertion loss and high cost caused by using a plurality of modulators in the prior art.

An embodiment of the present invention provides an optical transmitter, including:

a light source for generating an optical carrier;

a dual parallel Mach-Zengde MZM modulator for receiving a first binary electrical signal and a second binary electrical signal, according to the first binary electrical signal and the second way The power signal modulates the optical carrier to obtain a 4-ary optical signal;

a dual-drive MZM modulator for receiving a third binary electrical signal and a fourth binary electrical signal, according to the third binary electrical signal and the fourth binary electrical signal pair The 4-ary optical signal is modulated to obtain a hexadecimal optical signal.

The embodiment of the invention further provides an optical signal transmitting method, including:

Generating an optical carrier; Receiving a first binary electrical signal and a second binary electrical signal, and utilizing double parallel Mach-Zengde MZM modulation according to the first binary electrical signal and the second binary electrical signal Modulating the optical carrier to obtain a 4-ary optical signal;

Receiving a third binary electrical signal and a fourth binary electrical signal, according to the third binary electrical signal and the fourth binary electrical signal using a dual drive MZM modulator The 4-ary optical signal is modulated to obtain a hexadecimal optical signal.

An advantageous effect of the embodiment of the present invention is that a dual parallel MZM modulator modulates an optical carrier emitted by a light source into a 4-ary optical signal according to the first and second binary electrical signals, and then passes through the dual-drive MZM modulator. Modulating the 4-ary optical signal into a hexadecimal optical signal according to the third and fourth electrical signals, requiring fewer modulators, and synchronizing between the optical signal and the electrical signal is easier, and the insertion loss is smaller. Low and easy to integrate.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

1 is a schematic diagram showing the structure of an optical transmitter of a plurality of cascaded modulators in the prior art;

2 is a schematic structural diagram of an optical transmitter according to an embodiment of the present invention; FIG. 3 is a flowchart of a method for generating an optical signal according to an embodiment of the present invention;

4 is a structural diagram of an optical transmitter for generating a star-16QAM optical signal according to an embodiment of the present invention; FIG. 5 is a structural diagram of an optical transmitter for generating a square-16QAM optical signal according to an embodiment of the present invention;

FIG. 6 is a structural diagram of an optical transmitter for generating a 16APSK optical signal according to an embodiment of the present invention; FIG. 7 is a schematic structural diagram of a feedback control module according to an embodiment of the present invention.

detailed description

The technical solution in the embodiment of the present invention will be clarified in the following with reference to the accompanying drawings in the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is apparent that the described embodiments are only a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without departing from the inventive scope are the scope of the present invention.

FIG. 2 is a schematic structural diagram of an optical transmitter according to an embodiment of the present invention.

A light source 301, a dual parallel MZM modulator 302, and a dual drive MZM modulator 303 are included.

The light source 301 is configured to generate an optical carrier.

The dual parallel MZM modulator 302 is configured to receive a first binary electrical signal and a second binary electrical signal, according to the first binary electrical signal and the second binary binary An electrical signal modulates the optical carrier to obtain a 4-ary optical signal.

The dual-drive MZM modulator 303 is configured to receive a third binary electrical signal and a fourth binary electrical signal, according to the third binary electrical signal and the fourth binary The electrical signal modulates the quaternary optical signal to obtain a hexadecimal optical signal.

As an embodiment of the present invention, the light source 301 may include a laser.

As an embodiment of the present invention, the dual parallel MZM modulator 302 includes three bias terminals, wherein the two bias terminals are used to adjust the bias points of two MZM modulators in the dual parallel MZM modulator 302, respectively. The third bias terminal is configured to adjust a phase difference between the two MZM modulators such that the dual parallel MZM modulator generates different quaternary optical signals.

As an embodiment of the present invention, the method further includes a first amplifier for adjusting a high level and a low level of the first binary electrical signal, and a second amplifier for adjusting The high and low levels of the second binary electrical signal. As an alternative embodiment, the first amplifier and the second amplifier may be independent of the two MZM modulators or may be integrated into the two MZM modulators, respectively.

As an embodiment of the present invention, the dual-drive MZM modulator 303 includes two offset terminals, wherein the two bias terminals are respectively used to adjust two PMs in the dual-drive MZM modulator 303 (Phase Modulator) a bias point of the modulator to adjust a phase difference between the two PM modulators such that the dual-drive MZM modulator is based on the third binary electrical signal and the fourth binary The electrical signal modulates the 4-ary optical signal into different hexadecimal optical signals.

As an embodiment of the present invention, a third amplifier and a fourth amplifier are further included, the third amplifier is configured to adjust a high level and a low level of the third binary electric signal, and the fourth amplifier is used for adjusting The high and low levels of the fourth binary signal. As an optional embodiment, the third amplification The fourth amplifier and the fourth amplifier may be independent of the two PM modulators, or may be separately integrated into the two PM modulators.

As an embodiment of the present invention, an adjustable delay line is further provided between the dual parallel MZM modulator 302 and the dual drive MZM modulator 303 for the dual parallel MZM modulator 302 and the dual drive MZM modulator The optical signals between 303 are synchronized. The adjustable delay line can delay the 4-ary optical signal output by the dual parallel MZM modulator 302 by a predefined delay time, thereby synchronizing the dual parallel MZM modulator 302 and the dual drive MZM modulator 303, or The power of the fundamental frequency component is obtained by using the hexadecimal optical signal output by the dual-drive MZM modulator 303, and the feedback control signal generated by the power of the fundamental frequency component is used to synchronize between the dual parallel MZM modulator and the dual drive MZM modulator. Light signal.

As an embodiment of the present invention, the dual parallel MZM modulator 302 is further configured to synchronously input the first binary electrical signal and the second binary electrical signal, and the dual driving MZM modulator 303 The third binary electrical signal and the fourth binary electrical signal are also used for synchronous input.

Through the above embodiment, the optical carrier is modulated by the dual parallel MZM modulator according to the two binary electrical signals to generate a 4-ary optical signal, and then the dual-drive MZM modulator is used according to the third binary electrical signal and The fourth binary electric signal modulates the quaternary optical signal, and finally generates a hexadecimal optical signal, which requires fewer modulators, and the synchronization between the optical signal and the electrical signal is easy, and the insertion loss is low, and It is easy to integrate and has strong practicability. At the same time, this solution only needs four-way binary electric signal to drive the signal, which overcomes the inter-symbol interference problem caused by the 4-digit electrical signal and ensures the performance of the system.

FIG. 3 is a flowchart of a method for transmitting an optical signal according to an embodiment of the present invention.

Including step 401, an optical carrier is generated.

Step 402: Receive a first binary electrical signal and a second binary electrical signal, and use a dual parallel Mach-Zengde MZM according to the first binary electrical signal and the second binary electrical signal. The modulator modulates the optical carrier to obtain a 4-ary optical signal.

Step 403: Receive a third binary electrical signal and a fourth binary electrical signal, and use a dual-drive MZM modulator according to the third binary electrical signal and the fourth binary electrical signal. The quaternary optical signal is modulated to obtain a hexadecimal optical signal.

As an embodiment of the present invention, the light source may include a laser, and it is understood that the light source of the embodiment of the present invention may select a laser but is not limited thereto.

As an embodiment of the present invention, in step 402, adjusting the dual parallel MZM modulator The phase difference between the bias points of the two MZM modulators and the two MZM modulators causes the dual parallel MZM modulator to generate different quaternary optical signals.

As an embodiment of the present invention, the adjusting a phase difference between a bias point of two MZM modulators in the dual parallel MZM modulator and the two MZM modulators causes the dual parallel MZM modulator to generate Different 4-digit optical signals, including:

Adjusting the amplitude difference between the high level and the low level of the first binary electric signal to 2Vp, and adjusting the amplitude difference between the high level and the low level of the second binary electric signal to be 2Vp. Vp is a half-wave voltage of the dual parallel MZM modulator, for example, adjusting a high level of the first binary electrical signal and the second binary electrical signal to a half wave of the dual parallel MZM modulator Voltage (Vp), adjusting the low level of the first binary electrical signal and the second binary electrical signal to -Vp;

Setting the two bias points at a lowest point of a corresponding MZM modulator transmission curve such that the two MZM modulators generate a first binary phase shift keying signal (BPSK1) and a second binary phase shift key, respectively Control signal (BPSK2);

Adjusting a phase difference between the two MZM modulators to be π /2 such that a phase difference between the BPSK1 and the BPSK2 is π/2;

BPSK1 and BPSK2 with a phase difference of π /2 are combined to obtain a QPSK optical signal with constellation points in four quadrants.

As an embodiment of the present invention, the adjusting a phase difference between a bias point of two ΜΖΜ modulators in a dual parallel ΜΖΜ modulator and the two ΜΖΜ modulators causes the dual parallel ΜΖΜ modulator to generate Different 4-digit optical signals, including:

Adjusting the amplitude difference between the high level and the low level of the first binary electric signal to be Vp/2, and adjusting the amplitude difference between the high level and the low level of the second binary electric signal to be Vp/ 2. For example, amplifying the high level of the first and second binary electrical signals to Vp/4, and amplifying the low level of the first and second binary electrical signals to - Vp/4;

Setting the two bias points at π /2 of the corresponding MZM modulator transmission curve, so that the two ΜΖΜ modulators respectively generate two-phase amplitude shift keying signal 1 ( 2ASK1 ) and two-phase amplitude shift keying Signal 2 ( 2ASK2 );

Adjusting a phase difference between the two ΜΖΜ modulators to be π /2 such that a phase difference between the 2ASK1 and the 2ASK2 is π /2;

When 2ASK1 and 2ASK2 with a phase difference of π /2 are combined, the constellation points are all in the same quadrant. The QPSK optical signal, for example, is the QPSK optical signal located in the first quadrant.

Adjusting a difference between a high level and a low level of the first binary electric signal as Vp, wherein the Vp is a half wave voltage value of the dual parallel MZM modulator, and adjusting the second binary electric signal The amplitude difference between the high level and the low level is Vp/2, for example, the high level of the first binary electric signal is amplified to Vp/2, and the low level is amplified to -Vp/2, and the second way is The high level of the binary electrical signal is amplified to Vp/4 low level and amplified to -Vp/4;

Adjusting a phase difference between the two ΜΖΜ modulators to 0 such that a phase difference between the 2ASK1 and the 2ASK2 is 0;

The 2ASK1 and 2ASK2 with the phase difference of 0 are combined to obtain the 4 ASK amplitude-shift keyed 4ASK optical signal whose constellation points are all on the same coordinate axis.

As an embodiment of the present invention, in step 403, the phase difference between the two ΡΜ modulators is adjusted by adjusting the bias points of the two ΡΜ modulators in the dual drive ΜΖΜ modulator, the dual drive ΜΖΜ The modulator modulates the ternary optical signal according to the received third binary electrical signal and the fourth binary electrical signal to obtain different hexadecimal optical signals.

As an embodiment of the present invention, when the 4-ary optical signal is a QPSK optical signal whose constellation points are respectively located in four quadrants, the bias point of two ΡΜ modulators in the dual-drive ΜΖΜ modulator is adjusted, Adjusting a phase difference between the two ΡΜ modulators, the dual drive ΜΖΜ modulator according to the received third binary ternary electrical signal and the fourth binary electrical signal The 4-ary optical signal is modulated to obtain different hexadecimal optical signals, including:

The amplitude difference between the high level and the low level of the third binary electric signal is adjusted to Vq/2, and the difference between the high level and the low level of the fourth binary electric signal is adjusted to Vq, wherein Vq is the half-wave voltage of the dual-drive MZM modulator;

Adjusting the phase difference between the two PM modulators to π /4;

Combining the optical signals output by the two ΡΜ modulators with a phase difference of π /4 to obtain a star sixteen The quadrature amplitude modulation star- 16QAM optical signal.

As an embodiment of the present invention, when the 4-ary optical signal is a QPSK optical signal whose constellation points are all located in the same quadrant, the adjustment is performed by adjusting a bias point of two PM modulators in the dual-drive MZM modulator. a phase difference between the two PM modulators, the dual-drive MZM modulator according to the received third binary binary electrical signal and the fourth binary electrical signal, to the 4 The hexadecimal optical signal is modulated to obtain different hexadecimal optical signals including:

Adjusting the amplitude difference between the high level and the low level of the third binary electric signal to 2Vq, and the difference between the high level and the low level of the fourth binary electric signal is adjusted to 2Vq, wherein Vq is the half-wave voltage of the dual-drive MZM modulator;

Adjusting the phase difference between the two PM modulators to π /2;

The optical signals output by the two ΡΜ modulators with a phase difference of π /2 are combined to obtain a square hexadecimal quadrature amplitude modulation square- 16QAM optical signal.

As an embodiment of the present invention, when the 4-ary optical signal is a 4ASK optical signal whose constellation points are all located on the same coordinate axis, the bias point of the two PM modulators in the dual-drive MZM modulator is adjusted, Adjusting a phase difference between the two PM modulators, the dual-drive MZM modulator according to the received third binary binary electrical signal and the fourth binary electrical signal The 4-ary optical signal is modulated to obtain different hexadecimal optical signals, including:

Adjust the amplitude difference between the high level and the low level of the third binary electric signal to 2Vq, and adjust the amplitude of the high level and the low level of the second binary electric signal to 2Vq, where Vq is The half-wave voltage of the dual-drive MZM modulator;

Adjusting the phase difference between the two PM modulators to π /2;

The optical signals output by the two ΡΜ modulators having a phase difference of π /2 are combined to obtain a hexadecimal amplitude phase combined modulation 16APSK optical signal.

As an embodiment of the present invention, before the step 403, the optical signal between the dual parallel ΜΖΜ modulator and the dual drive ΜΖΜ modulator is synchronized by using an adjustable delay line.

After the step 403, the method further includes: analyzing a power level of the fundamental frequency component in the hexadecimal optical signal, or controlling the adjustable delay line, and predefining the delay of the 4-ary optical signal output by the dual parallel ΜΖΜ modulator The time to synchronize the optical signal between the dual parallel ΜΖΜ modulator and the dual drive modulator. According to the above embodiment, the dual-parallel MZM modulator modulates the light source into a 4-ary optical signal according to the first binary electrical signal and the second binary electrical signal, and uses the dual-drive MZM modulator according to the third path. The binary electrical signal and the fourth binary electrical signal modulate the quaternary optical signal to generate a hexadecimal optical signal, which requires fewer modulators, and the synchronization between the optical signal and the electrical signal is easy. The insertion loss is low, and it is easy to integrate. It has strong practicability. At the same time, the scheme only needs four binary electric signals, which overcomes the intersymbol interference caused by the 4-digit electrical signals and ensures the performance of the system. .

FIG. 4 is a structural diagram of an optical transmitter for modulating a star-16QAM optical signal according to an embodiment of the present invention. This embodiment includes: a laser 501, a dual parallel MZM modulator 502, an adjustable delay line 503, and a dual drive MZM modulator 504.

The four channels of data to be transmitted are the first binary electrical signal data1, the second binary electrical signal data2, the third binary electrical signal data3, and the fourth binary electrical signal data4, which are divided into two. For two groups, datal and data2—group, data3 and data4—groups, where datal, data2, data3, and data4 are binary electrical signals.

After the optical carrier is emitted from the laser 501, it enters the dual parallel MZM modulator 502 for spectral processing and is input to MZM1 and MZM2, respectively.

The dual parallel MZM modulator 502 internally integrates two parallel Mach-Zehnder modulators (MZM1 and MZM2) having the same performance. The dual parallel MZM modulator 502 has three bias terminals, namely, bias1, bias2, and bias3. Among them, bias1 and bias2 are used to adjust the bias points of MZM1 and MZM2, respectively, and bias3 is used to adjust the phase difference between MZM1 and MZM2. Datal and data2 each pass through the amplifier so that their high level is Vp and low level is -Vp. Vp is the half-wave voltage value of the double parallel MZM. Alternatively, the amplifier can be integrated into MZM1 and MZM2. Inside.

The amplified two electrical signals are loaded into the two RF ports of the dual parallel MZM modulator 502, respectively, to drive the two Mach-Zehnder modulators inside the dual parallel MZM modulator 502. Adjust the biasl, set the bias point of MZM1 to the lowest point of the MZM transmission curve, and load the amplified datal to obtain the BPSK1 optical signal (the constellation diagram of the BPSK1 optical signal is shown in Figure 4), and adjust the bias2 in the same way. Set the bias point of MZM2 to the lowest point of the MZM transmission curve, load the amplified data2, and obtain the BPSK2 optical signal, and then adjust the bias3 so that the phase difference between MZM1 and MZM2 is π/2. The constellation diagram of the BPSK2 optical signal with the phase difference of π /2 phase of the BPSK1 optical signal output by MZM 1 is as shown in FIG. 4). Thus, after combining BPSK1 and BPSK2 with a phase difference of π/2, a QPSK optical signal is obtained. The constellation diagram of the QPSK optical signal is as shown in FIG. 4, and the constellation points are respectively located in four quadrants. The QPSK optical signal, the combined output optical signal is the 4-ary optical signal, which in this example is a QPSK optical signal, and the optical signal is a 4-ary optical signal.

The QPSK signal from the dual parallel MZM modulator 502 is then synchronized by the adjustable delay line 503 for input to the dual drive MZM modulator 504.

Dual drive MZM integrates two parallel phase modulators with the same performance (PM1 and

PM2). Data3 passes through the amplifier so that its amplitude difference between high level and low level is Vq/2. Similarly, data4 passes through the amplifier, so that its amplitude difference between high level and low level is Vq, and Vq is half of double drive MZM. Wave voltage value. Optionally, when the PM1 receives the data3 electrical signal, the amplitude difference between the high level and the low level is changed to Vq/2 by the amplifier integrated in the PM1, and the PM2 is integrated into the PM1 when receiving the data4 electrical signal. The amplifier changes the amplitude difference between the high level and the low level to Vq.

The amplified data3 and data4 are loaded to the two RF ports of the dual-drive MZM modulator 504, and the phase difference between PM 1 and PM2 is π / by adjusting the bias terminals bias 1 and bias 2 of the dual-drive MZM modulator 504. 4. The optical signal generated by PM1 and the optical signal generated by ΡΜ2 are combined, and the modulator outputs a star-16QAM signal. The constellation diagram is as shown in FIG. Composition. ; , , ^ . , ' ' , ' , , This embodiment includes: a laser 501, a dual parallel MZM modulator 502, an adjustable delay line 503, and a dual drive MZM modulator 504.

After the datal passes through the amplifier, an electric signal with a high level of Vp/4 and a low level of -Vp/4 is obtained. The signal is used to drive the MZM1 of the dual parallel MZM modulator 502, and the baisl is adjusted, and the bias point of the MZM1 is set at The MZM transmission curve is π/2, so that the 2ASK1 optical signal with a certain extinction ratio can be obtained. Similarly, after the data2 passes through the amplifier, an electric signal with a high level of Vp/4 and a low level of -Vp/4 is obtained. The signal is used to drive the MZM2 of the dual parallel MZM modulator 502, and the bais2 is adjusted, and the bias point of the MZM2 is set at π/2, so that a 2ASK2 optical signal having a certain extinction ratio can be obtained, and the constellation of the 2ASK1 optical signal is obtained. The figure is shown in Figure 5; then by adjusting bias3, a 90 is produced between 2ASK1 and 2ASK2. The phase difference is 90 degrees out of phase with 2ASK1. The constellation diagram of the phase 2ASK2 is shown in Figure 5, so that 2ASK1 and 2ASK2 are vector superimposed to obtain the QPSK signal with the center point offset in the first quadrant.

The center point is biased in the first quadrant of the QPSK signal and then passed through the dual drive MZM to obtain the square-16QAM signal. The change for the dual drive MZM modulator 504 is that the data3 is amplified After the low level is -Vq, the high level is the electrical signal of Vq. Similarly, after the data4 is amplified, an electric signal with a high level of Vq and a low level of -Vq is obtained, and then the dual-drive MZM modulator 504 is jointly adjusted. The phase difference between the two PM modulators is 90. The PM1 modulator and the optical signal output by the PM2 modulator are combined, and after such adjustment, the square-16QAM signal can be obtained, and the constellation diagram is as shown in the figure.

FIG. 6 is a structural diagram of an optical transmitter for generating a 16APSK optical signal according to an embodiment of the present invention. This embodiment includes: a laser 501, a dual parallel MZM modulator 502, an adjustable delay line 503, and a dual drive MZM modulator 504.

After the datal passes through the amplifier, an electric signal with a high level of Vp/2 and a low level of -Vp/2 is obtained, and the signal is used to drive the MZM1 of the dual parallel MZM modulator 502, and the baisl is adjusted, so that the bias point of the MZM1 is set at π /2 of the transmission curve of MZM, so that the 2ASK1 optical signal with the extinction ratio of infinity can be obtained; after the data2 passes through the amplifier, the electric signal with the high level is Vp/4 and the low level is -Vp/4. The signal drives the MZM2 of the dual parallel MZM modulator 502, and adjusts bais2 such that the bias point of the MZM2 is at π/2, so that a 2ASK2 optical signal having a certain extinction ratio can be obtained, and the constellation diagram of the 2ASK1 optical signal is as shown in the figure. 6 is shown; then by adjusting bias3, the phase difference between 2ASK1 and 2ASK2 is 0, and the constellation of 2ASK2 which is 0 phase out of 2ASK1 is as shown in Fig. 6, so that 2ASK1 and 2ASK2 are vector superimposed. A 4ASK signal can be obtained. The constellation diagram of the 4ASK optical signal is as shown in FIG. 6, and the four constellation points are located on the positive half axis of the X-axis.

The 4ASK signal with the constellation point on the positive half of the X-axis is then subjected to the dual-drive MZM to obtain the 16APSK signal. The change for the dual-drive MZM modulator 504 is that the data3 is amplified to obtain an electrical signal with a low level of -Vq and a high level of Vq. Similarly, the data4 is amplified to obtain a low level of -Vq, a high level. The electrical signal, which is Vq, then jointly adjusts bias1 and bias2 of the dual-drive MZM modulator 504 such that the phase difference between PM1 and PM2 is 90. The optical signals output by PM1 and PM2 are combined, and the dual-drive MZM modulator 504 outputs a 16APSK signal. The constellation diagram is as shown in FIG. 6.

The optical transmitter of the structure shown in FIG. 4, FIG. 5 and FIG. 6 further includes a feedback control module, and the feedback control module is configured to obtain the power of the fundamental frequency component according to the hexadecimal optical signal output by the dual-drive MZM modulator. And generating a feedback control signal according to the power of the fundamental frequency component to control the adjustable delay line. The structure of the feedback control module, as shown in Figure 7, includes:

Photoelectric conversion unit 801, filtering unit 802, power detecting unit 803, inverter 804, amplifier

805.

From the spectrum point of view, if the dual parallel MZM modulator and the dual drive MZM modulator output optical signal If the number is accurately synchronized, a strong fundamental frequency signal component will appear on the spectral components. Conversely, when the synchronization condition is not satisfied, the fundamental frequency signal component will be weak, so the strength of the fundamental frequency signal component can be used as the feedback signal. Drive the adjustable delay line.

The photoelectric conversion unit 801 is connected to the output end of the hexadecimal optical signal of FIG. 5, FIG. 6 or FIG. 7 , that is, connected to the output end of the dual-drive MZM modulator, and converts the output optical signal into Electrical signals, such as photoelectric conversion using a PIN tube.

The filtering unit 802 is connected to the photoelectric conversion unit 801 to filter out a signal of a fundamental frequency component of the electrical signal, for example, using a high quality filter.

The power detecting unit 803 is connected to the filtering unit 802 to detect the power level of the filtered fundamental frequency component.

The inverter 804 is connected to the power detecting unit 803 to invert the fundamental frequency component detected by the power detecting unit 803. When the synchronization is very unsatisfactory, the power signal of the fundamental frequency component detected by the power detecting unit 803 is very small. At this time, a large signal is obtained through the inverter, and the signal is used to adjust the adjustable delay line in a wide range, thereby achieving synchronization as soon as possible. The purpose of the synchronization; conversely, when the synchronization has been ideal, the power signal of the fundamental frequency component detected by the power detecting unit 803 is relatively large, and a small signal is obtained through the inverter, and the adjustable delay line can be finely adjusted by the signal to achieve synchronization. Claim.

An amplifier 805, coupled to the inverter 804, for amplifying the output of the inverter 804 as a feedback control signal to control the adjustable delay line to synchronize between the dual parallel MZM modulator and the dual drive MZM modulator Optical signal.

The optical transmitter of the embodiment of the present invention can be applied to an optical communication device such as a base station using optical communication technology or the like.

The beneficial effects of the embodiments of the present invention are that the embodiments of the present invention implement the modulation of three different signals of Star-16QAM, 16APSK and Square-16QAM by using the same device, so that the cost of the optical transmitter is greatly reduced, and the existing transmission network is used. Among them, users have a wide variety of services, so the modulation format can be determined according to different services. The multi-format pattern modulation modulated by the embodiment of the present invention can carry a plurality of bit information through one symbol information, thereby improving the use efficiency and frequency band utilization of the optical fiber link and the amplifier, and the present invention is compared with the binary modulation pattern. Embodiments have better resistance to chromatic dispersion, polarization mode dispersion, and nonlinear noise. The optical transmitter embodiment of the present invention requires only a dual parallel MZM modulator and a dual drive MZM modulator. The system has a simple structure, low cost, and low insertion loss; and only requires four binary level signals (datal, data2). Data3 and data4), easy to generate, Will not cause serious ISI problems. The embodiment of the invention uses a small number of modulators and a single structure, so it is easy to integrate and has high use value.

It will be understood by those skilled in the art that all or part of the steps of implementing the foregoing embodiments may be performed by hardware related to program instructions. The foregoing program may be stored in a computer readable storage medium, and when executed, the program includes The foregoing steps of the method embodiment; and the foregoing storage medium includes: a medium that can store program codes, such as a ROM, a RAM, a magnetic disk, or an optical disk.

It should be noted that the above embodiments are only for explaining the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: The technical solutions described in the foregoing embodiments are modified, or the equivalents of the technical features are replaced by the same. However, the modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

Rights request

An optical transmitter characterized by comprising:

a light source for generating an optical carrier;

The optical transmitter according to claim 1, wherein the dual parallel MZM modulator comprises three bias terminals, wherein two bias terminals are respectively used to adjust the double parallel MZM modulator The bias point of the two MZM modulators, the third biasing terminal is used to adjust the phase difference between the two MZM modulators such that the dual parallel MZM modulator generates different quaternary optical signals.

The optical transmitter according to claim 2, further comprising a first amplifier and a second amplifier, wherein the first amplifier is configured to adjust a high level and a low level of the first binary electric signal Level, the second amplifier is configured to adjust a high level and a low level of the second binary electric signal.

The optical transmitter according to any one of claims 1 to 3, characterized in that the dual-drive MZM modulator comprises two bias terminals, wherein the two bias terminals are respectively used for adjusting the dual-drive MZM modulator a bias point of the two phase modulators PM to adjust a phase difference between the two PMs such that the dual-drive MZM modulator is based on the third-way binary electrical signal and the fourth path 2 The hexadecimal electrical signal modulates the quaternary optical signal into different hexadecimal optical signals.

The optical transmitter according to claim 4, further comprising a third amplifier and a fourth amplifier, wherein the third amplifier is configured to adjust a high level and a low level of the third binary electric signal Level, the fourth amplifier is configured to adjust a high level and a low level of the fourth binary electric signal.

The optical transmitter according to claim 4 or 5, further comprising an adjustable delay line between the dual parallel MZM modulator and the dual drive MZM modulator, for the dual parallel MZM The optical signal between the modulator and the dual drive MZM modulator is synchronized.

The optical transmitter according to claim 6, further comprising:

And a feedback control unit, configured to acquire power of the fundamental frequency component according to the hexadecimal optical signal, and generate a feedback control signal according to the power of the fundamental frequency component to control the adjustable delay line.

The optical transmitter according to claim 7, wherein the feedback control unit comprises: a photoelectric conversion unit that converts an optical signal output by the dual-drive MZM modulator into an electrical signal; and a filtering unit that filters out a fundamental frequency component of the electrical signal output by the photoelectric conversion unit;

a power detecting unit, configured to detect a power level of the filtered fundamental frequency component;

An inverter for inverting a power of a fundamental frequency component detected by the power detecting unit; an amplifier for amplifying an output of the inverter as a feedback control signal to control the adjustable delay line.

A method of generating an optical signal, comprising:

Generating an optical carrier;

Receiving a first binary electrical signal and a second binary electrical signal, and utilizing double parallel Mach-Zengde MZM modulation according to the first binary electrical signal and the second binary electrical signal Modulating the optical carrier to obtain a 4-ary optical signal;

The method according to claim 9, wherein the receiving the first binary electrical signal and the second binary electrical signal, according to the first binary electrical signal and the The second binary electrical signal modulates the optical carrier by using a dual parallel Mach-Zehnder MZM modulator to obtain a 4-ary optical signal comprising:

The phase difference between the bias points of the two MZM modulators in the dual parallel MZM modulator and the two MZM modulators is adjusted such that the dual parallel MZM modulators generate different quaternary optical signals.

The method according to claim 10, wherein the adjusting a phase difference between a bias point of two MZM modulators in the dual parallel MZM modulator and the two MZM modulators is such that The dual parallel MZM modulator generates different quaternary optical signals, including:

Adjusting the amplitude difference between the high level and the low level of the first binary electric signal to be 2Vp, and adjusting the amplitude difference between the high level and the low level of the second binary electric signal to be 2Vp, Vp is the half-wave voltage value of the dual parallel MZM modulator;

Setting the two bias points at the lowest point of the corresponding MZM modulator transmission curve, so that the two MZM modulators respectively generate the first binary phase shift keying signal BPSK1 and the second binary phase shift keying signal BPSK2; Adjusting a phase difference between the two MZM modulators to be π /2 such that a phase difference between the BPSK1 and the BPSK2 is π II;

The BPSK1 and the BPSK2 having a phase difference of π /2 are combined to obtain a QPSK optical signal in which the constellation points are respectively located in four quadrants.

The method according to claim 10, wherein the adjusting a phase difference between a bias point of two ΜΖΜ modulators of the dual parallel ΜΖΜ modulator and the two ΜΖΜ modulators is such that The dual parallel ΜΖΜ modulator generates different quaternary optical signals, including:

Adjusting the amplitude difference between the high level and the low level of the first binary electric signal to be Vp/2, and adjusting the amplitude difference between the high level and the low level of the second binary electric signal to be Vp/ 2, the Vp is a half-wave voltage value of the dual parallel MZM modulator;

Setting the two bias points at π /2 of the corresponding MZM modulator transmission curve such that the two ΜΖΜ modulators generate a first binary amplitude shift keying signal 2ASK1 and a second binary amplitude, respectively Shift key signal 2ASK2;

The 2ASK1 and the 2ASK2 having a phase difference of π /2 are combined to obtain a QPSK optical signal in which the constellation points are both located in the same quadrant.

Adjusting the amplitude difference between the high level and the low level of the first binary electric signal to be Vp, and adjusting the amplitude difference between the high level and the low level of the second binary electric signal to be Vp/2, The Vp is a half-wave voltage value of the dual parallel MZM modulator;

Setting the two bias points at π /2 of the corresponding MZM modulator transmission curve such that the two ΜΖΜ modulators respectively generate the first two-phase amplitude shift keying signal 2ASK1 and the second two-phase amplitude shift key Control signal 2ASK2;

The 2ASK1 and the 2ASK2 with a phase difference of 0 are combined to obtain a 4-ary amplitude shift keying 4ASK optical signal whose constellation points are all located on the same coordinate axis.

The method according to any one of claims 9 to 13, wherein the receiving the third binary electric signal and the fourth binary electric signal according to the third binary The electrical signal and the fourth binary electrical signal are modulated by the dual-drive MZM modulator to obtain the hexadecimal optical signal, including:

Adjusting a phase difference between the two PMs by adjusting a bias point of two phase modulators PM in the dual drive MZM modulator, the dual drive MZM modulator according to the received third pass binary The electrical signal and the fourth binary electrical signal modulate the quaternary optical signal to obtain different hexadecimal optical signals.

The method according to claim 14, wherein when the 4-ary optical signal is a QPSK optical signal whose constellation points are respectively located in four quadrants, the two PMs in the dual-drive MZM modulator are adjusted Offset point, adjusting a phase difference between the two PMs, the dual-drive MZM modulator according to the received third binary electrical signal and the fourth binary electrical signal, Modulating the quaternary optical signal to obtain different hexadecimal optical signals specifically includes:

Adjusting the amplitude difference between the high level and the low level of the third binary electric signal to Vq/2, and adjusting the difference between the high level and the low level of the fourth binary electric signal to Vq Where Vq is the half-wave voltage value of the dual-drive MZM modulator;

Adjusting the phase difference between the two PMs to π /4;

The two ΡΜ output optical signals with a phase difference of π /4 are combined to obtain a star hexadecimal orthogonal amplitude modulated star- 16QAM optical signal.

The method according to claim 14, wherein when the quaternary optical signal is a QPSK optical signal whose constellation points are all located in the same quadrant, the two of the dual-drive MZM modulators are adjusted by the adjustment.

a bias point of the PM, adjusting a phase difference between the two PMs, the dual-drive MZM modulator according to the received third binary binary electrical signal and the fourth binary electrical signal Modulating the quaternary optical signal to obtain different hexadecimal optical signals, including:

Adjusting a difference between a high level and a low level of the third binary electric signal to 2Vq, and adjusting a difference between a high level and a low level of the fourth binary electric signal to 2Vq Where Vq is the half-wave voltage value of the dual-drive MZM modulator;

Adjusting the phase difference between the two PMs to π /2;

The two ΡΜ output optical signals with a phase difference of π /2 are combined to obtain a square hexadecimal quadrature amplitude modulation square- 16QAM optical signal.

The method according to claim 14, wherein when the 4-ary optical signal is a 4ASK optical signal whose constellation points are all located on the same coordinate axis, the two PMs in the dual-drive MZM modulator are adjusted. Offset point, adjusting a phase difference between the two PMs, the dual-drive MZM modulator according to the received third binary electrical signal and the fourth binary electrical signal, Modulating the quaternary optical signal to obtain different hexadecimal optical signals, specifically including:

Adjusting the phase difference between the two PMs to π /2;

The two ΡΜ output optical signals having a phase difference of π /2 are combined to obtain a hexadecimal amplitude phase combined modulation 16APSK optical signal.

The method according to any one of claims 14 to 17, wherein the receiving the third binary electrical signal and the fourth binary electrical signal according to the third binary The electrical signal and the fourth binary electrical signal are modulated by the dual drive ΜΖΜ modulator to obtain the hexadecimal optical signal, and the hexadecimal optical signal is obtained before:

The optical signal between the dual parallel ΜΖΜ modulator and the dual drive ΜΖΜ modulator is synchronized using an adjustable delay line.

The method according to claim 18, wherein the receiving a third binary electrical signal and a fourth binary electrical signal, according to the third binary electrical signal and the The fourth binary electronic signal is modulated by the dual-drive ΜΖΜ modulator to obtain the hexadecimal optical signal, and after the hexadecimal optical signal is obtained, the method further includes:

The power of the fundamental frequency component in the 16-ary optical signal is analyzed, and the analysis result is fed back to the adjustable delay line for synchronous control.