WO2018161428A1 - Optically-controlled optical pam signal regeneration device - Google Patents

Abstract

Provided is an optically-controlled optical PAM signal regeneration device, comprising a power adapting unit, an optical clock control unit, and a PAM reshaping unit. The PAM reshaping unit is the core of a regenerator, and comprises a Mach-Zehnder interferometer (MZI) and a nonlinear optical loop mirror (NOLM). For a degraded optical PAM signal that needs to be regenerated, the power adapting unit first completes level matching between the inputted degraded optical PAM signal and the PAM reshaping unit, and then adjusts an optical clock signal power and a delay output by the optical clock control unit, and a phase shifter in the Mach-Zehnder interferometer (MZI) structure, so as to enable the PAM reshaping unit to operate normally. By changing parameters such as loss coefficients, fiber lengths, and nonlinear coefficients of the nonlinear optical loop mirror (NOLM), and coupling coefficients of front and rear couplers (C1, C2) in the Mach-Zehnder interferometer (MZI) structure, PAM reshaping units with different levels are designed, thereby completing the regeneration of the degraded optical PAM signal. The device of the invention can realize reshaping and retiming functions, and the number of regeneration levels can be flexibly configured.

Description

Light control optical PAM signal regeneration device Technical field

The invention belongs to the technical field of optical information processing, and more particularly to a light control optical PAM signal regeneration device.

Background technique

In optical fiber communication systems, optical signals are affected by factors such as fiber dispersion, fiber nonlinear effects, ASE noise accumulation of optical amplifiers, and interaction between channels, which leads to degradation of optical signals and ultimately limits systems and networks. Transmission rate and distance. Therefore, it is necessary to perform a regeneration process on the degraded signal. Although the traditional photoelectric light regeneration method is quite mature, it is difficult to meet the increasing demand for higher-speed data transmission due to the existence of an "electronic bottleneck". The all-optical regeneration technology of light-controlled light is considered to be the ultimate goal to solve this problem.

On the other hand, with the rapid development of applications such as cloud computing, big data and mobile internet, the transmission bandwidth requirements of the core network continue to increase, and channel capacity puts higher demands on spectrum efficiency. With the increasing application of PAM format high-order modulation signals in optical fiber communication systems and data center long-distance optical interconnections, the technical problems of PAM signal all-optical regeneration will soon be faced. At present, all-optical regenerator design schemes are mostly for traditional OOK signals and cannot be used for PAM signal regeneration.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art and provide a photo-controlled optical PAM signal reproducing device. The re-shaping process of the degraded optical PAM signal is used to obtain a high-quality optical PAM signal after regeneration, which has a simple structure and regenerative power. The advantage of a flat number for flexible design.

To achieve the above object, the present invention provides a light control optical PAM signal regeneration apparatus, comprising: a power adaptation unit, an optical clock control unit, and a PAM shaping unit;

The power adaptation unit amplifies the input degradation light PAM signal, adjusts the level of the degradation light PAM signal to a normal operating point of the PAM shaping unit, and then inputs the signal to the PAM shaping unit;

The optical clock control unit includes an optical clock signal generating module, a tunable fiber delay line, and an amplifier; wherein the optical clock signal generating module further includes a laser light source and an amplitude modulator;

The laser light source outputs continuous light to the amplitude modulator, and then uses the electric clock signal to drive the amplitude modulator, so that the amplitude modulator outputs the optical clock signal, and the optical clock signal is amplified by the amplifier and input to the adjustable fiber delay line, and is delayed by the adjustable fiber. The line adjusts the time delay of the optical clock signal to synchronize with the degraded optical PAM signal input into the high nonlinear optical fiber ring, and finally couples the synchronized optical clock signal into the highly nonlinear optical fiber ring;

The PAM shaping unit comprises a Mach-Zehnder interferometer and a high nonlinear fiber ring; the Mach-Zehnder interferometer is composed of a coupler C1 and a coupler C2 connected in tandem, and the upper arm of the Mach-Zehnder interferometer is connected in series. An optical isolator and a highly nonlinear fiber optic ring, the lower arm of which is connected in series with a phase shifter;

After receiving the degraded light PAM signal output by the power matching unit, the coupler C1 divides it into upper and lower paths, wherein the upper path light is input to the high nonlinear fiber ring through the optical isolator, and is in the high nonlinear fiber ring. The optical clock signal from the optical clock control unit has a nonlinear effect, producing a nonlinear phase-shifted optical signal that varies with input power; the downstream light passes through the phase shifter to produce a fixed phase shift that is independent of the input power. The optical signal; the upper and lower optical signals are coupled into the coupler C2, and two-beam interference occurs, and the regenerated optical PAM signal is coupled and output.

The object of the invention is achieved in this way:

The invention relates to a light control optical PAM signal regeneration device, comprising a power adaptation unit, an optical clock control unit and a PAM shaping unit; wherein the PAM shaping unit is the core of the regenerator, the Mach-Zehnder interferometer MZI and the high nonlinearity The optical fiber ring NOLM is composed of a degraded optical PAM signal that needs to be regenerated. First, the level matching between the input degraded optical PAM signal and the PAM shaping unit is completed by the power adaptation unit, and then the optical clock signal power output timing of the optical clock control unit is adjusted. The phase shifter in the extension and MZI structure enables the PAM shaping unit to work normally. By changing the loss coefficient, fiber length, nonlinear coefficient and other parameters of the high nonlinear fiber in the NOLM structure, and the coupling coefficient of the front and rear couplers in the MZI structure, The PAM shaping unit of different levels is used to complete the regeneration of the degraded optical PAM signal; thus, the present invention can perform the reshaping and retiming functions, and has the advantage that the number of reproduction levels can be flexibly designed.

DRAWINGS

1 is a structural diagram of a light control optical PAM signal reproducing apparatus of the present invention;

2 is a structural diagram of an optical clock light control unit;

3 is a waveform diagram of an input deteriorated PAM signal;

Figure 4 is a waveform diagram of a clock control signal;

Figure 5 is a waveform diagram of the output reproduced PAM signal;

detailed description

The specific embodiments of the present invention are described below in conjunction with the drawings in order to provide a better understanding of the invention. It is to be noted that in the following description, when a detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted herein.

Example

For the convenience of description, the relevant technical terms appearing in the specific embodiments are explained first:

PAM (Pulse Amplitude Modulation): amplitude modulation;

NOLM (Nonlinear fiber loop mirror) nonlinear optical fiber environment;

MZI (Mach-Zehnder interferometer) Mach-Zehnder interferometer;

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing the construction of a light control optical PAM signal reproducing apparatus.

In this embodiment, as shown in FIG. 1, a light control optical PAM signal regeneration apparatus includes: a power adaptation unit, an optical clock control unit, and a PAM shaping unit;

The power adapting unit amplifies the input degraded light PAM signal, adjusts the level of the degraded optical PAM signal to a normal operating point of the PAM shaping unit, and then inputs the signal to the PAM shaping unit;

As shown in FIG. 2, the optical clock control unit includes an optical clock signal generating module, an amplifier, and a tunable fiber delay line; wherein the optical clock signal generating module further includes a laser light source and an amplitude modulator;

The laser light source outputs continuous light to the amplitude modulator, and then uses the electric clock signal to drive the amplitude modulator, so that the amplitude modulator outputs the optical clock signal, and the optical clock signal is amplified by the amplifier and input to the adjustable fiber delay line, and is delayed by the adjustable fiber. The line adjusts the time delay of the optical clock signal to synchronize with the degraded light PAM signal input to the NOLM, and finally couples the synchronized optical clock signal into the NOLM;

In this embodiment, a wavelength division multiplexer may be added between the optical clock control unit and the high nonlinear optical fiber ring, and the synchronized optical clock signal is coupled to the high nonlinear optical fiber ring by the wavelength division multiplexer;

The power level of the optical clock control unit to generate the optical clock signal depends on the nonlinear coefficient of the highly nonlinear fiber in the NOLM structure and its length;

The output signal of the optical clock control unit is used to control the NOLM structure, and the regeneration function of the optical PAM signal can be realized by appropriately adjusting the power and delay of the optical clock signal output by the optical clock control unit;

The PAM shaping unit comprises a Mach-Zehnder interferometer MZI and a highly nonlinear fiber optic ring NOLM; the MZI is composed of a coupler C1 and a coupler C2 connected in tandem, and an optical isolator and a NOLM are sequentially connected in series on the upper arm of the MZI, and the lower arm thereof Connecting a phase shifter in series; the shaping function of the PAM shaping unit needs to be used in conjunction with the optical clock control unit;

After receiving the degraded light PAM signal output by the power matching unit, the coupler C1 divides it into upper and lower paths, wherein the upper path light is input to the NOLM through the optical isolator, and the light in the NOLM and the optical clock control unit The clock signal has a nonlinear effect, producing a nonlinear phase-shifted optical signal that varies with input power; the downstream light passes through the phase shifter to produce an optical signal that does not depend on the fixed phase shift of the input power; the upper and lower two The path light signal is coupled into the coupler C2 and double beam interference occurs, coupling out the outputted light PAM signal.

In this embodiment, by changing the loss coefficient, fiber length, nonlinear coefficient and other parameters of the high nonlinear fiber in the NOLM structure, and the coupling coefficient and phase shifter of the front and rear couplers in the MZI structure, different regeneration levels can be designed. Number of light-controlled optical PAM signal regenerators.

Instance

The invention will now be further described in detail by way of examples.

Let the input degraded light PAM signal be as shown in Fig. 3, which satisfies: the symbol rate is 10G baud, the duty ratio is 0.5, and the power of each level is 0.375W, 0.625W, 0.875W, 1.125W, and the average normalization. Amplitude noise jitter

The structure of the PAM shaping unit is the structure shown in FIG. 1. In this embodiment, in order to realize the shaping of the above-mentioned 4-level degraded light PAM signal, we select a loss coefficient of α=0.21km ^-1 and a nonlinear coefficient of γ=12W. ^-1 / km of high nonlinear fiber, on the basis of other optimization parameters using fiber length L = 3km, phase shifter Δφ = 3 / 2π, the coefficients of the front and rear coupler are ρ ₁ = 5.90% and ρ ₂ = 98.95%. Under the optimized parameters of the above PAM shaping unit, the PAM shaping unit can perform a shaping function on four level-degraded optical PAM signals having powers of 0.75 W, 1.25 W, 1.75 W, and 2.25 W, respectively.

The structure of the optical clock control unit is the structure shown in FIG. 2. In this embodiment, the optical clock signal output by the optical clock control unit is a periodic RZ square wave pulse signal, as shown in FIG. 4, in order to enable the PAM shaping unit to perform For the shaping function, the peak power of the optical clock control signal pulse output by the optical clock control unit should be set to 0.353 W and the duty ratio is equal to 0.5.

When the gain of the power adaptation unit is adjusted to G=2, the four levels of the degraded optical PAM signal, 0.375W, 0.625W, 0.875W, and 1.125W, can be amplified to the input level of the PAM shaping unit by 0.75 W, 1.25 W, 1.75W and 2.25W, thereby performing a reproduction function of the degraded light PAM signal.

Using a photo-controlled optical PAM signal reproducing device as shown in FIG. 1, the specific execution flow of the regenerative function is as follows: the degraded optical PAM signals with input levels of 0.375 W, 0.625 W, 0.875 W, and 1.125 W, respectively, are first passed. A power adaptation unit with a gain of G=2 adjusts the power to the operating point of the PAM shaping unit; the PAM signal after the power matching passes through the pre-coupler C1 with a coupling coefficient of 5.90%, and then divides the degraded optical PAM signal into upper, The next two paths, the path light in the NOLM and the optical clock signal from the optical clock control unit have a nonlinear effect, producing a nonlinear phase-shifted light that varies with the input power, in this embodiment, from the optical clock control unit. The optical clock signal is coupled to the NOLM through a wavelength division multiplexer, wherein the optical clock signal is an RZ square wave pulse having a peak power equal to 0.353 W and a duty ratio equal to 0.5; the downstream light passes through the phase shifter to generate an independent The fixed phase of the input power is shifted by 3π/2; finally, the two lights are double-beam interfered in the coupler C2, and the regenerated optical PAM signal is coupled and output, as shown in Fig. 5, which can be seen from the waveform diagram in Fig. 5. Out, every Noise level to give different degrees of inhibition; the same time, since the light output from the clock control unit are optical clock signal, under the control of the optically controlled optical reproducing apparatus PAM signal output from the reproduction signal is also retimed process.

While the invention has been described with respect to the preferred embodiments of the present invention, it is understood that the invention These variations are obvious as long as the various changes are within the spirit and scope of the invention as defined and claimed in the appended claims.

Claims (3)

A light control optical PAM signal regeneration device, comprising: a power adaptation unit, an optical clock control unit, and a PAM shaping unit; The power adaptation unit amplifies the input degradation light PAM signal, adjusts the level of the degradation light PAM signal to a normal operating point of the PAM shaping unit, and then inputs the signal to the PAM shaping unit; The optical clock control unit includes an optical clock signal generating module, an adjustable fiber delay line, and an amplifier; wherein the optical clock signal generating module further includes a laser light source and an amplitude modulator; The laser light source outputs continuous light to the amplitude modulator, and then uses the electric clock signal to drive the amplitude modulator, so that the amplitude modulator outputs the optical clock signal, and the optical clock signal is amplified by the amplifier and input to the adjustable fiber delay line, and is delayed by the adjustable fiber. The time delay of the line-adjusting optical clock signal is kept in synchronization with the degraded optical PAM signal input into the high nonlinear optical fiber ring, and finally the synchronized optical clock signal is coupled into the highly nonlinear optical fiber ring; The PAM shaping unit comprises a Mach-Zehnder interferometer and a high nonlinear fiber ring; the Mach-Zehnder interferometer is composed of a coupler C1 and a coupler C2 connected in tandem, and the upper arm of the Mach-Zehnder interferometer is connected in series. An optical isolator and a highly nonlinear fiber optic ring, the lower arm of which is connected in series with a phase shifter; After receiving the degraded light PAM signal output by the power matching unit, the coupler C1 divides it into upper and lower paths, wherein the upper path light is input to the high nonlinear fiber ring through the optical isolator, and is in the high nonlinear fiber ring. The optical clock signal from the optical clock control unit has a nonlinear effect, producing a nonlinear phase-shifted optical signal that varies with input power; the downstream light passes through a phase shifter to produce a fixed phase shift that is independent of the input power. The optical signal; the upper and lower optical signals are coupled into the coupler C2, and two-beam interference occurs, and the regenerated optical PAM signal is coupled and output. A light control optical PAM signal regeneration device, characterized in that a wavelength division multiplexer can be added between the optical clock control unit and the high nonlinear optical fiber ring, and the synchronized optical clock is passed through the wavelength division multiplexer. The signal is coupled into a highly nonlinear fiber optic ring. A light control optical PAM signal regeneration device is characterized in that the power level of the optical clock control unit to generate the optical clock signal depends on the nonlinear coefficient of the highly nonlinear optical fiber in the highly nonlinear fiber ring structure and its length.

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