WO2014206249A1

WO2014206249A1 - Device and method for improving modulation performance of mz modulator, and storage medium

Info

Publication number: WO2014206249A1
Application number: PCT/CN2014/080429
Authority: WO
Inventors: 周伟勤; 陈雪; 孟小波; 闫峥
Original assignee: 中兴通讯股份有限公司
Priority date: 2013-06-27
Filing date: 2014-06-20
Publication date: 2014-12-31
Also published as: CN104253654A

Abstract

Disclosed in an embodiment of the present invention are a device and method for improving the modulation performance of an MZ modulator, and a storage medium, the device comprising a laser, and further comprising: an arcsin transformation unit for conducting arcsin preprocessing on the input digital signal of an MZ modulator so as to allow the preprocessed signal to operate in an MZM nonlinear area without distortion; an digital-to-analog conversion (DAC) unit for converting the digital electrical signal processed by the arcsin transformation module into an analog electrical signal; an MZM unit for modulating the optical carrier outputted by the laser using the analog electrical signal converted by the DAC unit. Also disclosed is a method for improving the modulation performance of an MZ modulator. Through arcsin preprocessing of a digital signal, the technical solution of the present application can effectively inhibit the impact of the nonlinearity of MZ on-site modulation, thus increasing the output optical power of a transmitter.

Description

Apparatus and method for improving modulation performance of MZ modulator, storage medium

The invention relates to optical fiber communication, especially to coherent optical communication technology, and particularly relates to preprocessing of an originating signal and a modulation mechanism of a Mach-Zehnder modulator. Background technique

The coherent optical communication system based on the high-order modulation format adapts to the development of the current optical network, and constructs a high-speed, high-capacity, low-cost optical transmission network. Coherent optical communication systems based on high-order modulation formats are widely used in MZM for optical transmitter I/Q modulation. MZM is a non-linear modulator. When the amplitude of the drive signal is very small, MZM cannot achieve linear field modulation due to the extinction ratio. When the signal amplitude is increased to eliminate the effect of the undesired extinction ratio, if the signal amplitude exceeds the MZM linear field modulation interval, the signal will also introduce irreversible distortion, resulting in deterioration of the system bit error rate performance.

In a coherent optical communication system based on a high-order modulation format, the amplitude of the signal varies widely for a signal having a relatively large peak average power. When using MZM to linearly modulate a peak-to-average power ratio (PAP) signal, the drive signal cannot be controlled too small to avoid deterioration of modulation performance due to undesired extinction ratio. Since the signal has a high PAP, it is inevitable that some high-peak drive signals will fall in the nonlinear region, causing nonlinear distortion of the modulated signal. Therefore, how to overcome the impact of PAPR on MZM has become an urgent problem to be solved. Summary of the invention

The technical problem to be solved by the embodiments of the present invention is to provide an apparatus and method for improving the modulation performance of an MZ modulator and a storage medium to degrade the influence of the MZ field modulation nonlinearity. In order to solve the above technical problem, an embodiment of the present invention discloses an apparatus for improving the modulation performance of an MZ modulator, including a laser, and the apparatus further includes:

The inverse sine function transform unit performs an inverse sine function preprocessing on the input digital signal of the MZ modulator, so that the preprocessed signal operates in the MZM nonlinear region without distortion;

An analog-to-digital conversion (DAC) unit that converts the digital electrical signal processed by the inverse sine function transformation module into an analog electrical signal;

The MZM unit modulates the optical carrier of the laser output by using an analog electrical signal converted by the DAC unit.

Preferably, in the above apparatus, the inverse sine function preprocessing of the input digital signal of the MZ modulator means:

The inverse sine function transform unit performs a corresponding inverse transform on the input signal according to the signal response characteristic of the MZM.

Preferably, in the above apparatus, the inverse sine function conversion unit performs an inverse sine function preprocessing on the input digital signal according to the following formula:

In the above formula, for inputting a digital signal, ^ is a half-wave voltage of ΜΖΜ, and / is a coefficient for controlling the magnitude of the driving signal, and is an output digital signal preprocessed by an inverse sine function.

Preferably, in the above apparatus, the inverse sine function transformation unit includes one or more inverse sine function transformation modules.

Preferably, in the above apparatus, when the inverse sine function transformation unit includes a plurality of inverse sine function transformation modules, the analog-to-digital conversion (DAC) unit includes as many DACs as the number of inverse sine function transformation modules, The ΜΖΜ unit includes as many ΜΖΜ as the number of inverse sine function transformation modules. Preferably, in the above apparatus, when the inverse sine function transformation unit includes two inverse sine function transformation modules, the input digital signal is divided into I road and Q road, and two inverse sine function transformation modules respectively pair I and Q. The input digital signal of the circuit is subjected to an inverse sine function preprocessing, and the processed digital electrical signal is separately sent to a corresponding DAC in the analog-to-digital conversion (DAC) unit and a corresponding MZM in the MZM unit for processing.

Preferably, in the above apparatus, when the inverse sine function transformation unit includes two inverse sine function transformation modules, the two inverse sine function transformation modules respectively perform an inverse sine function on the input digital signals of the I and Q channels according to the following formula: Preprocessing: . Rek}| ≤ l 7. Re{ > 1 . Im{, < 1 lm{3⁄4}| > l

Among them, Re J , Im{5 „} are the input digital signals of I and Q in I/Q modulation process respectively, ^ is the half-wave voltage of MZM, and / is the coefficient of controlling the size of MZM driving signal, Rek} ' And Imk} ' are the output digital signals preprocessed by the inverse sine function of I and Q, respectively.

The invention also discloses a method for improving the modulation performance of an MZ modulator, comprising: performing an inverse sine function preprocessing on an input digital signal of the MZ modulator, so that the preprocessed signal works in a nonlinear region of the MZM without distortion, and then Converting the digital electrical signal preprocessed by the inverse sine function into an analog electrical signal;

The converted optical carrier is modulated by the converted analog electrical signal.

Preferably, in the above method, performing an inverse sine function on the input digital signal of the MZ modulator means:

According to the signal response characteristics of MZM, the input signal is inversely transformed accordingly. Preferably, in the above method, the input digital signal is subjected to an inverse sine function preprocessing according to the following formula:

— - arcsin(l), η - s \ > 1

In the above equation, for the input digital signal, ^ is the half-wave voltage of MZM, and / is the coefficient for controlling the magnitude of the MZM drive signal, which is the output digital signal preprocessed by the inverse sine function.

Preferably, the above method further includes:

The input digital signal of the MZ modulator is divided into one or more signals for processing.

Preferably, in the above method, when the input digital signal of the MZ modulator is divided into two signals for processing, the input digital signal is divided into I and Q channels, and the input digital signals of the I and Q channels are respectively corrected anyway. The string function is preprocessed, and the processed digital electrical signals are respectively converted into analog signals, and the converted optical signals output by the laser are modulated by the converted two analog electrical signals.

Preferably, in the above method, when the input digital signal of the MZ modulator is divided into two signals for processing, the inverse digital sine function preprocessing is performed on the input digital signals of the I and Q channels according to the following formula:

Among them, Rek}, Im{5„} are the input digital signals of I and Q, respectively, in the I/Q modulation process, ^ is the half-wave voltage of MZM, and / is the coefficient controlling the size of the MZM drive signal, Re } ' And Imk} ' are the output digital signals preprocessed by the inverse sine function of I and Q, respectively. A storage medium having stored therein a computer program configured to perform the aforementioned method of improving modulation performance of an MZ modulator.

The technical solution of the embodiment of the present invention performs the Arcsin (anti-sinusoidal function) preprocessing on the digital signal, thereby effectively suppressing the influence of the MZ field modulation nonlinearity and improving the output optical power of the transmitter. DRAWINGS

1 is a schematic structural diagram of an apparatus for improving MZM field modulation performance in a preferred embodiment of the present invention; FIG. 2 is a schematic diagram of the MZM field modulation performance of the 16QAM-CO-OFDM transmission system improved by the apparatus shown in FIG.

3 is a functional table diagram of a digital domain Arcsin transform unit implemented by the apparatus of FIG. 1. FIG. 4 is a flow chart of a method for improving MZM field modulation performance in accordance with a preferred embodiment of the present invention. detailed description

In order to make the objects, technical solutions and advantages of the present invention more comprehensible, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings. It should be noted that, in the case of no conflict, the features in the embodiments and the embodiments of the present application may be combined with each other arbitrarily.

Example 1

The present embodiment provides an apparatus for improving the modulation performance of an MZM. The apparatus includes a laser, an Arcsin transform unit, a DAC unit, and an MZM unit. The working principles of the various parts are described below.

a laser that provides an optical carrier;

The Arcsin transform module unit is used for Arcsin preprocessing of the digital signal input to the MZ modulator. The preprocessed signal can operate in the MZM nonlinear region without distortion.

Among them, the above Arcsin transformation module's Arcsin calculation method includes a table lookup method, but it is not limited to the table lookup method.

The above Arcsin transform module unit performs an inverse sine on the input digital signal of the MZ modulator. The function preprocessing refers to: The Arcsin transform unit performs corresponding inverse transformation on the input signal according to the signal response characteristic of the MZM.

In this embodiment, the Arcsin transform module can perform Arcsin preprocessing on the input digital signal according to the following formula:

In the above formula, for inputting a digital signal, ^ is a half-wave voltage of ΜΖΜ, and / is a coefficient for controlling the size of the driving signal, and is an output digital signal preprocessed by Arcsin.

After modulation according to the above formula, the input signal is linear with the output signal without being affected by the nonlinearity of the MZM.

The data input by the above Arcsin transform unit needs to be valued within the range [1 - ¹ ' ¹ ].

In addition, the DAC unit is configured to convert the digital electrical signal processed by the Arcsin transform module into an analog electrical signal.

The MZM unit is configured to modulate the optical carrier output by the laser by an analog electrical signal converted by the DAC unit for electrical/optical conversion.

Example 2

This embodiment provides a method for improving the modulation performance of an MZ modulator, which may be implemented by, but not limited to, the apparatus of the above Embodiment 1, which operates as follows:

Arcsin preprocessing is performed on the input digital signal of the MZ modulator, so that the preprocessed signal operates in the nonlinear region of the MZM without distortion, and then the digital electrical signal preprocessed by Arcsin is converted into an analog electrical signal;

Among them, the Arcsin preprocessing of the input digital signal of the MZ modulator is: according to the signal response characteristic of the MZM, the input signal is inversely transformed accordingly. In this embodiment, the input digital signal can be subjected to Arcsin preprocessing according to the following formula:

V.

— -arcsin (^-5 ), J <1

π

„,

■arcsi inn(l), Vl-

In the above formula, for the input digital signal, ^ is the half-wave voltage of MZM, and / is the coefficient for controlling the size of the MZM drive signal, which is the output digital signal preprocessed by Arcsin. It should be noted that, in practical applications, the input digital signal of the MZ modulator can be divided into one or multiple signals for processing.

Example 3

This embodiment provides a preferred apparatus for improving the MZM modulation performance, which is mainly optimized on the basis of the above-described Embodiment 1. It mainly focuses on the modulation mode of 16QAM, and proposes to divide the input signal into two signals of I and Q. At this time, the Arcsin transform module unit in the MZM modulation performance device can include two Arcsin transform modules, and the DAC unit includes The two DAC and MZM units include two MZMs, the structure of which is shown in Figure 1. The two Arcsin transform modules perform Arcsin preprocessing on the input digital signals of the I and Q channels of the input signal, respectively, which can be calculated according to the following formula.

V„,

.arcsin (77.Re{s"}) .Rek}|≤l

π

Re{3⁄4}'

R {^„} V _pi Re{^„} V _t

Arcsin „}|>1 ;/.Ιηψ„}|≤1

In the above formula, Re } , 2

\m{s _n is the input digital signal of I and Q, respectively, during I/Q modulation, V _p , is the half-wave voltage of MZM, ; / is the coefficient controlling the size of MZM drive signal, Re } ' and Imk} 'The output digital signals are preprocessed by Arcsin for I and Q respectively. It should be emphasized that the apparatus proposed in this embodiment is not limited to the scene use of the 16QAM-OFDM input signal. Depending on the scenario, adjustments can be made as appropriate.

The following describes how the preferred embodiment improves the MZM field modulation performance of the 16QAM-CO-OFDM system through the Arcsin transform module in conjunction with FIG. Preferably, the means for MZM modulation performance comprises a laser 18, a 16-QAM constellation mapping unit 10, a serial-to-parallel changing unit 11, an IFFT unit 12, a parallel string unit 13, a real Arcsin unit 14 and an imaginary part Arcsin unit 15, DAC unit 16 17, MZM unit 19, 20, and phase shifter 21. Among them, the real Arcsin unit 14 and the imaginary Arcsin unit 15 can be realized by look-up table method, as shown in Figure 3.

Example 4

The present embodiment provides a method for improving the MZM optical modulation performance of the 16QAM-CO-OFDM system based on the Arcsin transform. The implementation of the method may be implemented by the apparatus of the embodiment 3, and the specific implementation includes the following steps 400 to 406:

Step 400: The binary bit stream enters the 16QAM constellation mapping unit 10 to generate a 16QAM symbol ^s ". Step 401, the 16QAM symbol forms multiple parallel data through the serial-to-parallel transform unit 11. Step 402, the multiplex parallel data forms an OFDM signal through the IFFT unit 12. .

Step 403, the parallel OFDM signal data is subjected to serial-to-serial conversion unit 13 to form serial data. Step 404, the OFDM signals outputted by the serial-to-parallel transform unit 13 respectively obtain the real part and the imaginary part, and input the real part Arcsin unit 14 and the imaginary part Arcsin unit 15, and perform the following changes. „}|≤1

Re{3⁄4}'

Rek}| > l

^arcsin(^ Im{3⁄4}) ' |^ Im{3⁄4}|≤l

^Im i ^S n ^V P.

T ~~ ~Τ _a a _r rcsi _n H

n lj _ -τ- ^I ~ ^m ~i-^i ^V P.

Ττ-— I _T , 1 ₁

\n lm s„ \\>\

|lmk}| π |lm{5„}| 2 > " l Step 405, real part Arcsin transform unit 14 and imaginary part The digital signal output from the Arcsin transform unit 15 is subjected to analog-to-digital conversion via the DAC units 16, 17.

Step 406, the data output by the DAC unit 16, 17 is input to the MZM unit 19, 20 to modulate the optical carrier generated by the laser.

The key of the system solution is the Arcsin transformation of the digital domain, which can be implemented by using the look-up table method, specifically:

In the digital domain, the Arcsin transform can be performed by using the look-up table method. Firstly, the Arcsin table in the look-up table method is set. Different digits can be selected according to the accuracy requirement. Here, the N-bit Arcsin table is taken as an example. Figure 3 shows the Arcsin operation. The operation result corresponding to the input data of the unit.

The real Arcsin unit 14 and the imaginary Arcsin unit 15 signal are converted by the DAC unit 16, 17 and then enter the MZM unit 19, 20 as a drive signal. At this time, the output signals of the MZM unit 19, 20 are:

E _out = Ε _ιη · sin (-^ · Re{.(t)}') = Ε _ιη ^ Rc{s _n }

Pi

^E out = ^E , _n · sin (^- · Ιπψ )}') = E _m · η · {s _n )

Pi

It can be seen that the Arcsin transform method can make MZM meet the requirements of linear field modulation under the high PAPR of 16QAM-CO-OFDM system.

It can be seen from the above embodiment that the technical solution of the present invention uses the Arcsin transform operation unit to preprocess the signal before the originating DAC, so that the transmitted signal can work in the MZM field modulation nonlinear region, thereby avoiding the MZM working in the field modulation nonlinear region. The resulting system error rate is degraded and the system's efficiency in using the transmitter laser power is improved.

One of ordinary skill in the art can understand that all or part of the steps in the above methods can pass the process. The instructions are completed by instruction related hardware, and the program may be stored in a computer readable storage medium such as a read only memory, a magnetic disk or an optical disk. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the above embodiment may be implemented in the form of hardware or in the form of a software function module. This application is not limited to any specific combination of hardware and software.

Embodiments of the present invention also describe a storage medium in which a computer program is stored, the computer program being configured to perform the method of improving the modulation performance of the MZ modulator of the foregoing embodiment.

The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Industrial applicability

The invention performs Arcsin (anti-sinusoidal function) preprocessing on the digital signal, thereby effectively suppressing the influence of the MZ field modulation nonlinearity and improving the output optical power of the transmitter.

Claims

Claim

A device for improving the modulation performance of an MZ modulator, comprising a laser, the device further comprising: an inverse sine function transform unit for performing an inverse sine function preprocessing on the input digital signal of the MZ modulator, so that the preprocessed signal operates MZM nonlinear region without distortion;

2. The apparatus of claim 1, wherein the inverse sine function preprocessing of the input digital signal of the MZ modulator is:

3. The apparatus according to claim 2, wherein the inverse sine function transformation unit is preprocessed according to a lower chord function:

The apparatus according to any one of claims 1 to 3, wherein the inverse sine function transformation unit comprises one or more inverse sine function transformation modules.

5. The apparatus according to claim 4, wherein, when the inverse sine function transform unit includes a plurality of inverse sine function transform modules, the analog-to-digital conversion (DAC) unit includes as many as the inverse sine function transform module The DAC, the ΜΖΜ unit includes as many ΜΖΜ as the number of inverse sine function transformation modules.

6. The apparatus of claim 5, wherein the inverse sine function transformation unit comprises two When the inverse sine function transformation module divides the input digital signal into I and Q channels, the two inverse sine function transformation modules respectively perform inverse sine function preprocessing on the input digital signals of I and Q, respectively, and then process the processed The digital electrical signals are respectively sent to corresponding DACs in the analog-to-digital conversion (DAC) unit and corresponding MZMs in the MZM unit for processing.

7. The apparatus according to claim 6, wherein, when the inverse sine function transformation unit comprises two inverse sine function transformation modules, the two inverse sine function transformation modules respectively input the input numbers of the I and Q channels according to the following formula: The signal is preprocessed with an inverse sine function:

^arcsin(^ Re{3⁄4}) , |^ Re{3⁄4}|≤l π . ^rcSm(1) —国. ' ^ 〉 ¹

!!mk}| ^π | ^Im k}|

Among them, Re J , \m{s _n are the input digital signals of I and Q channels in I/Q modulation process respectively, ^ is the half-wave voltage of MZM, and / is the coefficient of controlling the size of MZM driving signal, Rek}' And Imk}' are the output digital signals preprocessed by the I and Q paths through the inverse sine function.

8. A method of improving the modulation performance of an MZ modulator, comprising:

The input digital signal of the MZ modulator is subjected to an inverse sine function preprocessing, so that the preprocessed signal operates in the nonlinear region of the MZM without distortion, and then the digital electrical signal preprocessed by the inverse sine function is converted into an analog electrical signal;

9. The method of claim 8, wherein the inverse sine function preprocessing of the input digital signal of the MZ modulator is:

According to the signal response characteristics of MZM, the input signal is inversely transformed accordingly.

10. The method of claim 9, wherein the input digital signal is subjected to an inverse sine function preprocessing according to the following formula:

In the above formula, for inputting a digital signal, ^ is the half-wave voltage of MZM, and / is a coefficient for controlling the magnitude of the MZM drive signal, and is an output digital signal preprocessed by an inverse sine function.

The method according to any one of claims 8 to 10, wherein the method further comprises: dividing the input digital signal of the MZ modulator into one or more signals for processing.

12. The method according to claim 11, wherein, when the input digital signal of the MZ modulator is divided into two signals for processing, the input digital signal is divided into I road and Q road, respectively, for the I road and the Q road. The digital signal is input to perform an inverse sine function preprocessing, and then the processed digital electrical signal is separately converted into an analog signal, and the converted optical signal is modulated by the converted two analog electrical signals.

13. The method according to claim 12, wherein, when the input digital signal of the MZ modulator is divided into two signals for processing, the inverse digital sine function preprocessing is performed on the input digital signals of the I and Q channels according to the following formula: :

V,

― arcsin (^ Im{3⁄4}) η - lm - < 1

π

Arcsin lm{3⁄4}| > l

Where Rek} and lm{s _n } are the input digital signals of I and Q, respectively, in the I/Q modulation process, ^ is the half-wave voltage of MZM, and / is the coefficient controlling the size of the MZM drive signal, Re } ' And Imk} ' are the output digital signals preprocessed by the inverse sine function of I and Q, respectively.

A storage medium storing a computer program, the computer program being configured to perform the method of improving the modulation performance of the MZ modulator according to any one of claims 8 to 13.