阅读说明：本技术 一种全光相位量化方法、全光相位量化器 (All-optical phase quantization method and all-optical phase quantizer ) 是由 不公告发明人 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种全光相位量化方法,将具有相位差的两路光信号量化为具有不同强度的多路光信号；对所述多路光信号进行光电转换为电信号并放大；选取判决阈值与所述放大后的多路电信号进行比较后,转换为数字电信号；将所述数字电信号中周期性重复部分进行恢复,形成完整的数字信号输出。本发明公开了一种全光相位量化方法及装置能够有效提升相位量化分辨率(量化位数),降低光相位量化结构复杂度,为全光模数转换器奠定基础。(The invention discloses an all-optical phase quantization method, which quantizes two optical signals with phase difference into multiple optical signals with different intensities; photoelectrically converting the multiple optical signals into electric signals and amplifying the electric signals; selecting a decision threshold value, comparing the decision threshold value with the amplified multi-channel electric signals, and converting the decision threshold value into digital electric signals; and recovering the periodic repeated part in the digital electric signal to form a complete digital signal output. The invention discloses a method and a device for quantizing an all-optical phase, which can effectively improve the phase quantization resolution (quantization bit number), reduce the complexity of an optical phase quantization structure and lay a foundation for an all-optical analog-digital converter.)

1. A method for quantizing an all-optical phase, characterized by comprising the steps of:

quantizing the two optical signals with the phase difference into a plurality of optical signals with different intensities;

photoelectrically converting the multiple optical signals into electric signals and amplifying the electric signals;

selecting a decision threshold value, comparing the decision threshold value with the amplified multi-channel electric signals, and converting the decision threshold value into digital electric signals;

and recovering the periodic repeated part in the digital electric signal to form a complete digital signal output.

2. The all-optical phase quantization method according to claim 1, characterized in that:

the quantizing the two optical signals with the phase difference into multiple optical signals with different intensities specifically includes:

two optical signals having a phase difference are quantized into 5 optical signals having different intensities.

3. The all-optical phase quantization method according to claim 2, characterized in that:

after comparing the selected decision threshold with the amplified multi-channel electric signal, converting the selected decision threshold into a digital electric signal, which specifically comprises the following steps:

and converting the multipath electric signals into 10 grades of digital electric signals according to the decision threshold value.

4. The all-optical phase quantization method according to claim 3, characterized in that:

the recovering of the periodic repeated part in the digital electric signal specifically comprises:

the quantization result with a phase difference larger than 2 pi is restored to the correct quantization value and the quantization level is increased to 19.

5. An all-optical phase quantizer, comprising:

the quantization module is used for quantizing the two optical signals with the phase difference into a plurality of optical signals with different intensities;

the conversion amplification module is used for performing photoelectric conversion on the multi-path optical signals into electric signals and amplifying the electric signals;

the comparison module is used for comparing the amplified multi-channel electric signals with a selection judgment threshold value;

and the recovery module is used for recovering the periodic repeated part in the digital electric signal to form complete digital signal output.

6. The all-optical phase quantizer of claim 5, wherein:

the quantization module is a cascade multi-mode coupling interferometer MMI.

7. The all-optical phase quantizer of claim 6, wherein:

the cascade multimode coupling interferometer MMI is formed by splicing a first-stage multimode coupling interferometer and a second-stage multimode coupling interferometer, and the whole device is provided with two input ports and five output ports.

Technical Field

The invention relates to the technical field of optical analog/digital converters, in particular to a full-optical phase quantization method and a full-optical phase quantizer.

Background

Quantization is an important part of the signal processing process, and in recent years, with the development of photon technology, more and more light quantization schemes are going to the field of vision of people and are widely researched by people. The quantization schemes can be classified into intensity quantization, frequency quantization and phase quantization according to different quantization modes. Intensity quantization has limitations in obtaining high resolution quantization; the scheme based on frequency quantization usually needs to utilize a nonlinear effect to carry out frequency conversion, the length of a nonlinear medium is usually large, the required intensity of an excitation light source is large, and the scheme of the whole system is usually complex and is not beneficial to integration. The scheme based on phase quantization is simple in structure, works in a linear region, and is the quantization scheme which is most beneficial to integration.

The quantifiable phase range of the existing all-optical phase quantizer is limited, and the quantizer is only fixed at 0-2 pi, and has lower effective digit. Aiming at the existing 3.3-bit all-optical phase quantization, the bit expansion scheme of the all-optical phase quantizer is provided, and the effective bit of the all-optical phase quantizer can be improved to 4.3 bits under the condition of not changing the structure of the original device.

Disclosure of Invention

The invention provides a bit expansion scheme based on the existing bit all-optical phase quantizer, the scheme does not need to change the device, the operation is simple, and the performance is obviously improved.

The invention provides a method for quantizing an all-optical phase, which comprises the following steps:

quantizing the two optical signals with the phase difference into a plurality of optical signals with different intensities;

photoelectrically converting the multiple optical signals into electric signals and amplifying the electric signals;

selecting a decision threshold value, comparing the decision threshold value with the amplified multi-channel electric signals, and converting the decision threshold value into digital electric signals;

and recovering the periodic repeated part in the digital electric signal to form a complete digital signal output.

Further, the quantizing the two optical signals with the phase difference into multiple optical signals with different intensities specifically includes:

two optical signals having a phase difference are quantized into 5 optical signals having different intensities.

Further, after comparing the selected decision threshold with the amplified multiple electrical signals, the selected decision threshold is converted into a digital electrical signal, which specifically comprises:

and converting the multipath electric signals into 10 grades of digital electric signals according to the decision threshold value.

Further, the recovering the periodic repetition part in the digital electrical signal specifically includes:

the quantization result with a phase difference larger than 2 pi is restored to the correct quantization value and the quantization level is increased to 19.

In another aspect, the present invention provides an all-optical phase quantizer, including:

the quantization module is used for quantizing the two optical signals with the phase difference into a plurality of optical signals with different intensities;

the conversion amplification module is used for performing photoelectric conversion on the multi-path optical signals into electric signals and amplifying the electric signals;

the comparison module is used for comparing the amplified multi-channel electric signals with a selection judgment threshold value;

and the recovery module is used for recovering the periodic repeated part in the digital electric signal to form complete digital signal output.

Further, the quantization module is a cascade multimode coupling interferometer MMI.

Further, the cascade multi-mode coupling interferometer MMI is composed of a first stage multi-mode coupling interferometer (MMI)^1st) With second-stage multimode-coupled interferometers (MMI)^2nd) The whole device is provided with two input ports and five output ports.

An effective bit number expansion scheme based on a 3.3-bit all-optical phase quantizer is provided, the scheme does not need to change an original device, the implementation method is simple, and the effect is obvious.

Drawings

FIG. 1 is a diagram of a quantizer of the present invention;

FIG. 2 is a diagram illustrating a quantization curve and a coding scheme according to the present invention;

FIG. 3 is a diagram illustrating the quantization results of the quantizer according to the present invention for different input phase differences;

FIG. 4 is a diagram illustrating the bit expansion result of the quantizer according to the present invention;

FIG. 5 is an experimental diagram of the quantizer bit number expansion scheme of the present invention;

FIG. 6 is a diagram of the quantizer direct test data derivation final quantization result process of the present invention;

FIG. 7 is a diagram of the experimental results of the bit phase quantizer bit number expansion scheme of the quantizer of the present invention;

fig. 8 is a schematic diagram of a cascaded MMI structure used by the quantizer of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Fig. 1 shows the system structure of a 3.3-bit quantizer, and Es and Ep are the inputs of the 3.3-bit all-optical phase quantizer, which can be expressed as

Wherein P, ω andrespectively showing the power, angular frequency and initial phase of the two beams,indicating the phase difference of Es and Ep. From such input, the output results of 5 channels of the quantizer are calculated, which results

The transmission curve is plotted based on the output results to obtain the results in fig. 2(a), and a suitable decision threshold (red dashed line in fig. 2 (a)) is selected to divide the phase range of 0-2 pi into 10 quantization levels.

In practical operation, the outputs of the five channels can be detected and determined, and then encoded according to the method shown in fig. 2(b), so as to obtain the final quantization result.

Fig. 3 shows the quantization results of the all-optical phase quantizer for different input phase differences, with the phase difference of Es and Ep on the abscissa and the quantization scale on the ordinate. Since the phase of light has a periodicity of 2 π, the phase difference isWith a phase difference ofThe quantization results of Es and Ep are the same, so for the accuracy of the quantization results, it is necessary to ensure that the phase difference between Es and Ep is 2^πWithin.

The bit expansion scheme proposed by us utilizes the periodic quantization result and restores the quantization result when the phase difference is larger than 2 pi to the correct quantization value through algorithm restoration. Taking the phase difference range 0-4 pi in fig. 3 as an example, the corresponding relationship between the quantization result obtained by the algorithm recovery and the phase difference is as shown in fig. 4, and the result proves that the quantizer can perform 4.3-bit quantization within the range of 4 pi.

The recovery algorithm used is briefly described below.

Suppose the data sequence before recovery is y (known), y being at [ - λ, λ]Within the interval of (3), the sampling period of the sequence is T; the recovered data sequence is r (unknown) assuming its upper bound β_gAre known, andthe difference between r and y is defined as x, x being r-y.

Defining modulo operationsWherein

Defining a differential operation Δ y_k＝y_k+1-y_k。

Choosing the proper integer N can prove thatWhen it is takenWe can solve for the Nth order difference Δ of x from only the known y^Nx，Δ^Nx＝Δ^Nr-Δ^Ny＝M_λ(Δ^Ny)-Δ^Ny。

The summation operation S is defined:the nth order difference of x exists as the following recursion formula: delta^n-1x＝SΔⁿx + k (N) N2, 3.., N-1, N, wherein,starting from N ═ N, Δ can be calculated sequentially by iteration^N-1x，Δ^N-2x, a. Finally, the recovered sequence r is y + x.

We have experimentally verified the bit extension scheme of the 3.3-bit all-optical phase quantizer. Fig. 5(a) is an experimental layout, and light is input to the chip from the vertical coupler on the left side and is divided into two paths by the beam splitter. One of the light passes through a thermal phase modulator to introduce additional phase into the light. The additional phase of the light can be changed by 0-4 pi by adjusting the voltage value loaded on the thermal phase modulator. FIG. 5(b) is a graph showing normalized output results of 5 output ports when an applied voltage is applied to the thermo-modulator so that the phase difference between Es and Ep varies from 0 to 4 π. This result is decided and encoded to obtain the result of fig. 5 (c). The result corresponds to the sequence before recovery in the recovery algorithm.

Let λ be 0.5, since the phase of light varies from 0-4 π, which is in the range of two times 2 π, the upper bound β of the recovered sequence is easily obtained_g2 λ 1. The sequence is normalized correspondingly, so that the original 0-9 quantization level is [ -0.5.0.5 [ -]In this case, y satisfying the requirement is obtained as shown in FIG. 6 (a). Calculated according to a formulaThe Nth order difference of y is calculated as shown in FIG. 6(b), and the Nth order difference Δ of the difference x is calculated^Nx＝M_λ(Δ^Ny)-Δ^Ny, as shown in FIG. 6(c)As shown. K (n) (n is 2) is calculated, k (2) is 0, and the difference x is calculated by 2-step difference of x according to the iterative summation formula, and the result is shown in fig. 6 (d). Adding the sequence y before recovery to the difference sequence to obtain a recovered sequence r, as shown in fig. 6(e), performing denormalization on r, and recovering the normalized quantization level to the original length, thereby obtaining a quantization result of the final use of the quantization extension scheme, as shown in fig. 6 (f).

Since the applied voltage of the thermal phase modulator is nonlinear with the generated phase shift, we change the abscissa in fig. 6(c) and (f) into the phase difference of Es and Ep according to the relationship between the applied voltage of the thermal phase modulator and the generated phase shift to obtain the result diagram in fig. 7, in order to more intuitively see the quantization capability of the phase quantizer. Fig. 7(a) is a result of not using the bit number extension scheme, showing a quantizer significance of 3.3 bits; fig. 7(b) is a result after using the digit extension scheme, which shows that the significant digit is 4.3 bits. The above experimental results prove that the bit expansion scheme of the 3.3-bit all-optical phase quantizer is feasible.

The all-optical phase quantizer we use is a cascaded MMI fabricated on an SOI platform, the specific structure of which is shown in fig. 8. Fig. 8(a) is a cross-sectional view of a device showing a specific material of a cascaded MMI fabricated based on an SOI platform, and it can be seen that the silicon waveguide has a thickness of 220nm and is surrounded by a silicon dioxide substrate and a cladding layer. FIG. 8(b) is a three-dimensional block diagram of the device showing the specific shape of the cascaded MMI, which can be seen to consist of a first level MMI (MMI)^1st) And a second level MMI (MMI)^2nd) The device is formed by splicing, and the whole device is provided with two input ports and five output ports.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive faculty, based on the technical solutions of the present invention.