Integrated optical FIR (Finite Impulse Response) filter and filtering method

Abstract

The invention discloses an integrated optical FIR (Finite Impulse Response) filter and a filtering method, and relates to the technical field of integrated photonic devices and optical communication. Light splitting is carried out through the multiple adjustable beam splitters, phase compensation and phase regulation are carried out through the multiple first phase shifters, and therefore the equivalent function of the digital processing domain FIR filter is achieved in the optical signal propagation process, and the calculation requirement needed by current mass optical signal data can be better met. According to the optical FIR filter, the delay lines are connected with the adjustable beam splitters, the step-by-step light splitting delay structure of the optical FIR filter is achieved, compared with the structure that light splitting is conducted firstly and then delay is conducted in the prior art, the number of unit delay lines can be reduced, the adjustable beam splitters and the delay lines jointly form the optical path difference with the next adjustable beam splitter, and the optical path difference between the adjustable beam splitters and the next adjustable beam splitter is reduced. And the required length of the delay line is further shortened, so that the propagation length required by the optical signal data in the optical FIR filter is reduced, and the transmission loss of the optical signal in the optical FIR filter is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated photonic devices and optical communications, and in particular relates to an integrated optical FIR filter and a filtering method. Background Art

[0002] With the continuous development of optical fiber communication technology, it has become a key technology supporting communication transmission. In order to improve the efficiency of optical fiber communication, the modulation of high-order optical signals is currently achieved by modulating the amplitude and phase of light waves to increase the information capacity of a single channel, and the scale of the channel is expanded by time, wavelength and polarization, which further improves the transmission rate and capacity of optical fiber communication. Although these technologies have improved the transmission rate and capacity of optical fiber communication, they have also brought problems in signal crosstalk and equalization processing, especially in a multi-input and multi-output optical communication environment. Signal crosstalk and distortion face more complex time distribution and spatial distribution, which greatly increases the optical signal data that needs to be processed.

[0003] In order to solve the problems of signal crosstalk and distortion, optical filters are usually used to process optical signals. Current optical filters usually split the optical signal through a splitter first, and then delay it through a delay line; in order to process the increasing optical signal data, the size of the current splitter, the number and length of the delay lines are constantly increasing, but these have led to further increase in the loss of optical signals during the transmission process of the optical filter; in addition, the increasing optical signal data has put forward higher requirements on the computing power of the optical filter, and the current optical filter is limited by its structure of splitting first and then delaying, which makes it unable to adapt well to the current filtering needs of massive optical signal data. Therefore, in view of the defects of existing optical filters, there is an urgent need for an integrated optical FIR filter and filtering method to solve them. Summary of the invention

[0004] The present invention aims to provide an integrated optical FIR filter and a filtering method to solve the above technical problems. By using an adjustable beam splitter connected in sequence by delay lines, the optical signal is split and delayed, thereby reducing the optical signal transmission loss of the optical FIR filter.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides an integrated optical FIR filter, including: a plurality of delay lines, a plurality of adjustable beam splitters connected in sequence, a plurality of first phase shifters and a beam combiner;

[0006] The first adjustable beam splitter is used to receive a damaged optical signal and split the damaged optical signal to obtain a first optical signal and a third optical signal, and then input the third optical signal into the next adjustable beam splitter through the delay line;

[0007] Except for the first and last adjustable beam splitters, the other adjustable beam splitters are used to receive the third optical signal output by the previous adjustable beam splitter, split the third optical signal to obtain the first optical signal, and then input the split third optical signal into the next adjustable beam splitter through the delay line;

[0008] When the third optical signal is input to the last adjustable beam splitter, the last adjustable beam splitter inputs the third optical signal as the first optical signal to the first phase shifter;

[0009] The first phase shifter is used to receive the first optical signal output by the adjustable beam splitter, and perform phase compensation and phase control on the first optical signal to obtain a second optical signal;

[0010] The beam combiner is used to combine the second optical signal output by the first phase shifter into a restored optical signal;

[0011] The input end of the first adjustable beam splitter serves as the input port of the integrated optical FIR filter for receiving the damaged optical signal; the output end of the beam combiner serves as the output port of the integrated optical FIR filter for outputting the restored optical signal.

[0012] It can be understood that, compared with the prior art, the present invention performs light splitting through multiple adjustable beam splitters, and performs phase compensation and phase control with multiple first phase shifters, thereby realizing the equivalent function of the digital processing domain FIR filter in the process of optical signal propagation. Through the structure of step-by-step light splitting delay, and the form of phase control and phase compensation by multiple first phase shifters, it can better adapt to the computing requirements required for the current massive optical signal data. The present invention realizes the structure of step-by-step light splitting delay of the optical FIR filter by connecting multiple adjustable beam splitters through delay lines. Compared with the structure of first light splitting and then delaying in the prior art, the number of unit delay lines can be reduced, and the optical path difference between the adjustable beam splitter and the next adjustable beam splitter is formed together by the adjustable beam splitter and the delay line, further shortening the required length of the delay line, thereby reducing the propagation length required for the optical signal data in the optical FIR filter, thereby reducing the transmission loss of the optical signal in the optical FIR filter.

[0013] As a preferred solution, the adjustable beam splitter comprises: a first beam splitter, a second phase shifter and a second beam splitter;

[0014] A first output end of the first beam splitter is connected to an input end of the second phase shifter;

[0015] The second output end of the first beam splitter is connected to the second input end of the second beam splitter;

[0016] The output end of the second phase shifter is connected to the first input end of the second beam splitter;

[0017] The first output end of the second beam splitter is used to output a third optical signal;

[0018] The second output end of the second beam splitter is used to output the first optical signal;

[0019] The input end of the first beam splitter of the first adjustable beam splitter is used to receive the damaged optical signal, and the input ends of the first beam splitters of the other adjustable beam splitters are used to receive the third optical signal.

[0020] This preferred solution performs light splitting by a first beam splitter and a second beam splitter, and then adjusts the ratio of light splitting by a phase shift value of a second phase shifter, so that different adjustable beam splitters can extract different ratios of the first optical signal, thereby realizing step-by-step light splitting of the damaged optical signal, thereby reducing the number of subsequent unit delay lines, and further reducing the transmission loss of the optical signal in the optical FIR filter.

[0021] As a preferred solution, when the number of the adjustable beam splitters is an integer power of 2, the beam combiner adopts an MMI beam combiner array;

[0022] The MMI combiner array comprises a plurality of sequentially connected MMI combiner units;

[0023] The first MMI combiner unit includes an MMI combiner; the number of MMI combiners in the other MMI combiner units is twice the number of MMI combiners in the previous MMI combiner unit; except for the last MMI combiner unit, each of the MMI combiners in the other MMI combiner units is connected to two MMI combiners in the next MMI combiner unit;

[0024] When the number of the adjustable beam splitters is not an integer power of 2, the beam combiner adopts an all-in-one MMI beam combiner.

[0025] This preferred solution uses beam combiners of different structures according to the number of adjustable beam splitters, so that the beam combiner can better meet the actual filtering requirements of the optical FIR filter, avoiding the low filtering efficiency of the optical FIR filter due to poor performance of the beam combiner when facing massive optical signal data, and improving the filtering efficiency of the optical FIR filter.

[0026] As a preferred embodiment, the first adjustable beam splitter extracts the first optical signal from the damaged optical signal according to a preset tap amplitude coefficient; except for the first and last adjustable beam splitters, the other adjustable beam splitters extract the first optical signal from the third optical signal according to a preset tap amplitude coefficient; and the first phase shifter performs phase compensation and phase control on the first optical signal according to a preset tap phase coefficient.

[0027] This preferred solution extracts a first optical signal from a damaged optical signal by presetting a tap amplitude coefficient, and performs phase compensation and phase control on the first optical signal by using a tap phase coefficient, thereby realizing the equivalent function of a digital processing domain FIR filter during optical signal propagation, and improving the filtering capability of an optical FIR filter by using an equivalent FIR filter.

[0028] As a preferred solution, the waveguide length between each of the first phase shifters and the beam combiner is the same.

[0029] This preferred solution can ensure that the beam combiner evenly combines the second optical signal by setting the waveguide length between the first phase shifter and the beam combiner to be the same, thereby improving the filtering accuracy of the optical FIR filter.

[0030] As a preferred solution, the sampling interval of the integrated optical FIR filter is determined by the adjustable beam splitter and the delay line.

[0031] This preferred solution determines the sampling interval of the integrated optical FIR filter through an adjustable beam splitter and a delay line, ensuring that the damaged optical signal collected by the integrated optical FIR filter can better conform to the structure of the step-by-step beam splitting delay, thereby improving the filtering efficiency of the integrated optical FIR filter.

[0032] Accordingly, an embodiment of the present invention provides a filtering method of an integrated optical FIR filter, which is applicable to the integrated optical FIR filter as described above, and includes:

[0033] Inputting a damaged optical signal to the first adjustable beam splitter, controlling the first adjustable beam splitter to split the damaged optical signal to obtain a first optical signal and a third optical signal, and then inputting the third optical signal to the next adjustable beam splitter through a delay line;

[0034] Controlling the other adjustable beam splitters except the first and the last one to receive the third optical signal output by the previous adjustable beam splitter, and splitting the third optical signal to obtain the first optical signal, and then inputting the split third optical signal into the next adjustable beam splitter through the delay line;

[0035] When the last adjustable beam splitter receives the third optical signal, controlling the last adjustable beam splitter to input the third optical signal as the first optical signal into the first phase shifter;

[0036] The first phase shifter is controlled to receive the first optical signal output by the adjustable beam splitter, and phase compensation and phase regulation are performed on the first optical signal to obtain a second optical signal. Then, the beam combiner is controlled to combine the second optical signal into a restored optical signal to complete filtering of the damaged optical signal.

[0037] It can be understood that, compared with the prior art, the present invention inputs a damaged optical signal to the first adjustable beam splitter, then controls the first adjustable beam splitter to split the damaged optical signal to obtain a first optical signal and a third optical signal, and then inputs the third optical signal to the next adjustable beam splitter through a delay line, and then controls the subsequent adjustable beam splitter to split and delay the third optical signal, thereby realizing step-by-step splitting delay. In the form of step-by-step splitting delay, compared with the structure of first splitting and then delaying in the prior art, the number of unit delay lines can be reduced, and the optical path difference between the adjustable beam splitter and the next adjustable beam splitter is jointly formed by the adjustable beam splitter and the delay line, thereby further shortening the required length of the delay line, thereby reducing the propagation length required for the optical signal data in the optical FIR filter, thereby reducing the transmission loss of the optical signal in the optical FIR filter. The present invention performs light splitting through an adjustable beam splitter and performs phase compensation and phase regulation through a first phase shifter, thereby realizing the equivalent function of a digital processing domain FIR filter in the process of optical signal propagation. Through the structure of step-by-step light splitting delay and the form of phase regulation and phase compensation by multiple first phase shifters, it can better adapt to the computing requirements required for the current massive optical signal data.

[0038] As a preferred solution, inputting the damaged optical signal to the first adjustable beam splitter specifically includes:

[0039] Obtaining an effective refractive index of the adjustable beam splitter, a length of the adjustable beam splitter, an effective refractive index of a delay line, and a length of the delay line;

[0040] The sampling interval is determined according to the effective refractive index of the adjustable beam splitter, the length of the adjustable beam splitter, the effective refractive index of the delay line and the length of the delay line:

[0041] Δt=(n effs L s +n effd L d ) / c,

[0042] Where Δt is the sampling interval, n effs is the effective refractive index of the tunable beam splitter, n effd is the effective refractive index of the delay line, Ls is the length of the adjustable beam splitter, L d is the length of the delay line, c is the speed of light;

[0043] The damaged optical signal is input to the first adjustable beam splitter according to the sampling interval.

[0044] This preferred solution determines the sampling interval of the integrated optical FIR filter through an adjustable beam splitter and a delay line, ensuring that the damaged optical signal collected by the integrated optical FIR filter can better conform to the structure of the step-by-step beam splitting delay, thereby improving the filtering efficiency of the integrated optical FIR filter.

[0045] As a preferred solution, controlling the first adjustable beam splitter to split the damaged optical signal to obtain the first optical signal and the third optical signal specifically includes:

[0046] Obtaining a tap amplitude coefficient of the first adjustable beam splitter;

[0047] Normalizing the tap amplitude coefficient according to a preset normalization method, and using the square value of the normalized tap amplitude coefficient as the splitting ratio of the first adjustable beam splitter;

[0048] According to the splitting ratio, the first adjustable beam splitter is controlled to split the damaged optical signal to obtain a first optical signal and a third optical signal.

[0049] As a preferred solution, controlling the first phase shifter to receive the first optical signal output by the adjustable beam splitter, and performing phase compensation and phase control on the first optical signal to obtain a second optical signal specifically includes:

[0050] Acquire a tap phase coefficient of each first phase shifter, and determine a phase control value of each first phase shifter according to the tap phase coefficient and in combination with a preset waveguide phase error;

[0051] The first phase shifter is controlled to receive the first optical signal output by the adjustable beam splitter, and phase compensation and phase control are performed on the first optical signal according to the phase control value to obtain a second optical signal.

[0052] This preferred solution uses multiple adjustable beam splitters to extract signals, and multiple first phase shifters to perform phase compensation and phase control, thereby realizing the equivalent function of a digital processing domain FIR filter during the optical signal propagation process, which can better adapt to the computing requirements required for the current massive optical signal data and improve the filtering efficiency of the integrated optical FIR filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1: A schematic diagram of the structure of an integrated optical FIR filter provided by an embodiment of the present invention;

[0054] Figure 2 : A schematic structural diagram of a first adjustable beam splitter provided in an embodiment of the present invention;

[0055] Figure 3 : A schematic diagram of the structure of an adjustable beam splitter other than the first and last adjustable beam splitters provided in an embodiment of the present invention;

[0056] Figure 4 : A schematic diagram of the structure of a beam combiner using an MMI beam combiner array provided in an embodiment of the present invention;

[0057] Figure 5 : A schematic diagram of a tap structure provided by an embodiment of the present invention;

[0058] Figure 6 : A flow chart of a tap amplitude coefficient normalization process provided by an embodiment of the present invention;

[0059] Figure 7 : A schematic diagram of the steps of a filtering method of an integrated optical FIR filter provided by an embodiment of the present invention;

[0060] Among them, 101: damaged optical signal; 102: adjustable beam splitter; 103: delay line; 104: first phase shifter; 105: combiner; 106: restored optical signal; 107: first optical signal; 108: second optical signal; 109: tap structure; 110: third optical signal; 1021: first beam splitter; 1022: second phase shifter; 1023: second beam splitter; 201: MMI combiner unit; 2011: MMI combiner. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Embodiment 1

[0063] Please refer to Figure 1 , is a schematic diagram of the structure of an integrated optical FIR filter provided by an embodiment of the present invention, Figure 2 , is a schematic structural diagram of a first adjustable beam splitter provided in an embodiment of the present invention, Figure 3, is a schematic diagram of the structure of an adjustable beam splitter other than the first and last adjustable beam splitters provided in an embodiment of the present invention, Figure 4 , is a schematic diagram of the structure of a beam combiner using an MMI beam combiner array provided in an embodiment of the present invention.

[0064] The integrated optical FIR filter comprises: a plurality of delay lines 103, a plurality of adjustable beam splitters 102 connected in sequence, a plurality of first phase shifters 104 and a beam combiner 105;

[0065] The first adjustable beam splitter 102 is used to receive the damaged optical signal 101, and split the damaged optical signal 101 to obtain a first optical signal 107 and a third optical signal 110, and then input the third optical signal 110 to the next adjustable beam splitter 102 through the delay line 103;

[0066] Except for the first and last adjustable beam splitters 102, the other adjustable beam splitters 102 are used to receive the third optical signal 110 output by the previous adjustable beam splitter 102, split the third optical signal 110 to obtain the first optical signal 107, and then input the split third optical signal 110 to the next adjustable beam splitter 102 through the delay line 103;

[0067] When the third optical signal 110 is input to the last adjustable beam splitter 102, the last adjustable beam splitter 102 inputs the third optical signal 110 as the first optical signal 107 to the first phase shifter 104;

[0068] The first phase shifter 104 is used to receive the first optical signal 107 output by the adjustable beam splitter 102, and perform phase compensation and phase control on the first optical signal 107 to obtain a second optical signal 108;

[0069] The beam combiner 105 is used to combine the second optical signal 108 output by the first phase shifter 104 into a restored optical signal 106;

[0070] The input end of the first adjustable beam splitter 102 serves as the input port of the integrated optical FIR filter for receiving the damaged optical signal 101 ; the output end of the beam combiner 105 serves as the output port of the integrated optical FIR filter for outputting the restored optical signal 106 .

[0071] In this embodiment, the adjustable beam splitter 102 includes: a first beam splitter 1021, a second phase shifter 1022 and a second beam splitter 1023;

[0072] The first output end of the first beam splitter 1021 is connected to the input end of the second phase shifter 1022;

[0073] The second output end of the first beam splitter 1021 is connected to the second input end of the second beam splitter 1023;

[0074] The output end of the second phase shifter 1022 is connected to the first input end of the second beam splitter 1023;

[0075] The first output end of the second beam splitter 1023 is used to output the third optical signal 110;

[0076] The second output end of the second beam splitter 1023 is used to output the first optical signal 107;

[0077] The input end of the first beam splitter 1021 of the first adjustable beam splitter 102 is used to receive the damaged optical signal 101 , and the input ends of the first beam splitters 1021 of the other adjustable beam splitters 102 are used to receive the third optical signal 110 .

[0078] In this embodiment, light is split by a first beam splitter and a second beam splitter, and the ratio of light splitting is adjusted by a phase shift value of a second phase shifter, so that different adjustable beam splitters can extract different ratios of the first optical signal, thereby realizing step-by-step light splitting of the damaged optical signal, thereby reducing the number of subsequent unit delay lines, and further reducing the transmission loss of the optical signal in the optical FIR filter.

[0079] In this embodiment, if Figure 4 As shown, when the number of the adjustable beam splitters is an integer power of 2, the beam combiner adopts an MMI beam combiner array;

[0080] The MMI combiner array comprises a plurality of sequentially connected MMI combiner units 201;

[0081] The first MMI combiner unit 201 includes an MMI combiner 2011; the number of MMI combiners 2011 in other MMI combiner units 201 is twice the number of MMI combiners 2011 in the previous MMI combiner unit 201; except for the last MMI combiner unit 201, each of the MMI combiners 2011 in other MMI combiner units 201 is connected to two MMI combiners 2011 in the next MMI combiner unit 201;

[0082] When the number of the adjustable beam splitters is not an integer power of 2, the beam combiner adopts an all-in-one MMI beam combiner.

[0083] It should be noted that an MMI combiner refers to a combiner based on the principle of multi-mode interference (MMI). By adopting an MMI combiner array, the advantages of a 2-in-1 combiner that is easy to achieve high uniformity and low loss can be brought into play, and a high-efficiency, high-quality addition function of the combiner 105 can be achieved, thereby improving the filtering efficiency and accuracy of the integrated optical FIR filter.

[0084] This embodiment uses beam combiners with different structures according to the number of adjustable beam splitters, so that the beam combiner can be more in line with the actual filtering requirements of the optical FIR filter, avoiding the low filtering efficiency of the optical FIR filter due to poor performance of the beam combiner when facing massive optical signal data, and improving the filtering efficiency of the optical FIR filter.

[0085] It should be noted that if Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, in this embodiment, the number of adjustable beam splitters 102 and the first phase shifters 104 is the same, and a delay line 103 is arranged between every two adjustable beam splitters 102. Therefore, please refer to Figure 5 , is a schematic diagram of a tap structure provided by an embodiment of the present invention, wherein an adjustable beam splitter 102, a first phase shifter 104 and a delay line 103 form a tap structure 109. When the number of the adjustable beam splitters 102 is n, the number of the first phase shifters 104 is also n, and the number of the delay lines 103 is n-1. At this time, the i-th first phase shifter 104 and the i-th delay line 103 connected to the i-th adjustable beam splitter 102 are regarded as the i-th tap structure 109, as shown in FIG. Figure 4 As shown, the i-th delay line 103 is used to delay the third optical signal 110 output by the i-th adjustable beam splitter 102;

[0086] It should be noted that in Figure 1 On the basis shown, since no splitting is performed at the last adjustable beam splitter 102 (i.e., the nth adjustable beam splitter 102), the last tap structure 109 (i.e., the nth tap structure 109) does not include the delay line 103. On this basis, the last adjustable beam splitter 102 (i.e., the nth adjustable beam splitter 102) can also be removed from the integrated optical FIR filter, and only the last first phase shifter 104 (i.e., the first phase shifter 104 in the nth tap structure) is retained, which can further reduce the number of components required for the integrated optical FIR filter and reduce costs.

[0087] In this embodiment, the first adjustable beam splitter 102 extracts the first optical signal 107 from the damaged optical signal 101 according to a preset tap amplitude coefficient; except for the first and last adjustable beam splitters 102, the other adjustable beam splitters 102 extract the first optical signal 107 from the third optical signal 110 according to the preset tap amplitude coefficient; the first phase shifter 104 performs phase compensation and phase control on the first optical signal 107 according to the preset tap phase coefficient.

[0088] It should be noted that the integrated optical FIR filter described in this embodiment realizes the FIR (Finite Impulse Response) filtering function. The core difference from the electrical domain FIR filter is that since the total optical signal power is constant in optics, the optical signal will be attenuated in a corresponding proportion after partial extraction of the optical signal. The filtering function of the FIR filter can be described as in, It is used to represent the tap coefficient of the i-th tap structure in the FIR filter, z is the change of z in the signal processing process, the tap coefficient can be decomposed into the tap amplitude coefficient and the tap phase coefficient. There is a relatively mature general solution method for the filter function, tap coefficient and z change of the FIR filter, so this embodiment will not be described in detail here.

[0089] In order to enable the integrated FIR filter described in this embodiment to realize the function of FIR filtering, it is necessary to split the damaged optical signal and the third optical signal, and perform phase compensation and phase control on the first optical signal, which will be described in detail below. In order to enable the integrated FIR filter described in this embodiment to adapt to the characteristic that the total optical signal in optics is constant, it is necessary to control the proportion of the extracted first optical signal through the tap amplitude coefficient.

[0090] Specifically, as described above, the integrated optical FIR filter of this embodiment is provided with n tap structures 109. First, the tap coefficient of each tap structure 109 is solved, and then decomposed into the tap amplitude coefficient and the tap phase coefficient of each tap structure 109. Since there is a relatively mature general solution method, this embodiment will not be elaborated here.

[0091] First, please refer to Figure 6 , is a flowchart of a tap amplitude coefficient normalization process provided by an embodiment of the present invention, defining the tap amplitude coefficient of the i-th tap structure as a i , define X iThe ratio of the optical power corresponding to the optical signal input to the i-th tap structure 109 (i.e., the i-th tunable beam splitter 102) to the optical power corresponding to the damaged optical signal 101 input to the integrated optical FIR filter (i.e., the optical power corresponding to the damaged optical signal 101 input to the first tunable beam splitter 102). Here, i represents the current i-th tap (1 ≤ i ≤ n). It should be noted that when the tap structure 109 is the first tap structure 109, the optical signal here refers to the damaged optical signal 101, and when the tap structure 109 is other tap structures 109 except the first tap structure 109, the optical signal here refers to the third optical signal 110.

[0092] Therefore, the ratio of the first optical signal 107 extracted by the i-th tunable beam splitter is defined as The third optical signal 110 transmitted to the (i + 1)-th tunable beam splitter is attenuated, and the ratio of its optical power to the optical power corresponding to the damaged optical signal 101 input to the integrated optical FIR filter (i.e., the optical power corresponding to the damaged optical signal 101 input to the first tunable beam splitter 102) is defined as After that, under the condition of i < n, the normalized tap amplitude coefficient a of the i-th tunable beam splitter is calculated in a loop NORi , after the loop ends, the normalized tap amplitude coefficients a NOR1 ~a NORn are obtained. Calculate the square value of the normalized tap amplitude coefficient a NORi of the i-th tunable beam splitter to obtain the splitting ratio a NORi 2 of the i-th tunable beam splitter. Then, the i-th tunable beam splitter 102 extracts the first optical signal 107 according to their respective splitting ratios a NORi 2 .

[0093] Secondly, as Figure 2 and Figure 3 show, the tunable beam splitter 102 of this embodiment constitutes the structure of a Mach-Zehnder interferometer. The first beam splitter 1021 and the second beam splitter 1023 are 3dB couplers (three-dB directional couplers). By adjusting the phase shift value θ of the second phase shifter 1022, the complex amplitude ratio (i.e., amplitude control) of the first optical signal 107 output by the tunable beam splitter 102 and the third optical signal 110 output to the next tunable beam splitter 102 can be regulated, so that the integrated optical FIR filter meets the requirements of FIR filtering. Among them, by adjusting the phase shift value θ of the second phase shifter 1022 in the i-th tunable beam splitter 102, the complex amplitude ratio of the first optical signal 107 output by the i-th tunable beam splitter is determined to be e i(π-θ) / 2cos(θ / 2), and determine that the complex amplitude ratio of the third optical signal 110 output from the i-th adjustable beam splitter to the i+1-th adjustable beam splitter is e i(3π-θ) / 2 sin(θ / 2), so that the i-th adjustable beam splitter satisfies |e i(π-θ) / 2 cos(θ / 2)|=a NORi .

[0094] Next, the phase compensation is defined as the phase error due to the difference in waveguide lengths The complex amplitude phase difference π between the first optical signal 107 output from the adjustable beam splitter 102 and the third optical signal 110 output to the next adjustable beam splitter, and the phase control of the i-th first phase shifter 104 is defined as the tap phase coefficient b of the i-th tap structure 109 where it is located. i , therefore, the phase shift value of the i-th first phase shifter 104 is set to Wherein mod represents remainder. By setting the phase shift value of the i-th first phase shifter 104, the phase compensation and phase control of the first optical signal 107 by the i-th first phase shifter 104 are realized.

[0095] It should be noted that a waveguide is a spatially non-uniform structure that can propagate light, also known as an optical waveguide or a dielectric optical waveguide. There are currently mature algorithms for solving the phase error caused by the difference in waveguide length, which will not be described in detail in this embodiment.

[0096] Through the light splitting and amplitude control of the i-th adjustable beam splitter 102 in the above embodiment, and the phase compensation and phase control of the i-th first phase shifter 104, the i-th tap structure 109 can realize multiplying the second optical signal input to the beam combiner by the complex coefficient Then, the output of each tap structure 109 is summed by the beam combiner to realize the filtering function of the FIR filter.

[0097] Through the above embodiments, the tap function and multiplication function of the electrical domain FIR filter are merged into the adjustable beam splitter, thereby reducing the total number of components and the control complexity of the integrated optical FIR filter.

[0098] This embodiment extracts a first optical signal from a damaged optical signal by presetting a tap amplitude coefficient, and performs phase compensation and phase control on the first optical signal by using a tap phase coefficient, thereby realizing the equivalent function of a digital processing domain FIR filter during optical signal propagation, and improving the filtering capability of an optical FIR filter by using an equivalent FIR filter.

[0099] In this embodiment, the waveguide length between each of the first phase shifters 104 and the beam combiner 105 is the same.

[0100] In this embodiment, by setting the waveguide length between the first phase shifter and the beam combiner to be the same, it is possible to ensure that the beam combiner evenly combines the second optical signal, thereby improving the filtering accuracy of the optical FIR filter.

[0101] In this embodiment, the sampling interval of the integrated optical FIR filter is determined by the adjustable beam splitter 102 and the delay line 103 .

[0102] In an optional embodiment, the optical path between the i-th tap structure 109 and the i+1-th tap structure 109 is determined by the adjustable beam splitter 102 and the delay line 103. The accumulated delay difference of the optical path for the optical signal determines the sampling interval of the integrated optical FIR filter. The sampling interval of the integrated optical FIR filter is Δt=(n effs L s +n effd L d ) / c,n effs and n effd are the effective refractive indices of the tunable beam splitter and the delay line, L s and L d are the lengths of the adjustable beam splitter and the delay line, respectively, and c is the speed of light. In particular, since the sampling interval and the sampling frequency f are inversely proportional, the time delay difference between the i-th tap structure 109 and the i+1-th tap structure 109 must satisfy Δt=1 / f.

[0103] This embodiment determines the sampling interval of the integrated optical FIR filter through an adjustable beam splitter and a delay line, ensuring that the damaged optical signal collected by the integrated optical FIR filter can better conform to the structure of step-by-step beam splitting delay, thereby improving the filtering efficiency of the integrated optical FIR filter.

[0104] Through the step-by-step splitting and delay architecture of this example, compared with the existing structure of splitting first and then delaying in existing optical filters, the number of unit delay lines can be reduced from n(n-1) / 2 to (n-1). The adjustable beam splitter and delay line in each tap structure together constitute the required optical path difference between it and the next tap structure, further shortening the length of the delay line, reducing the device size required for the integrated optical FIR filter and the propagation length required for the optical signal, thereby reducing the transmission loss of the optical signal.

[0105] This embodiment performs light splitting through multiple adjustable beam splitters, and performs phase compensation and phase control with multiple first phase shifters, thereby realizing the equivalent function of the digital processing domain FIR filter in the process of optical signal propagation. Through the structure of step-by-step light splitting delay, and the form of phase control and phase compensation by multiple first phase shifters, it can better adapt to the computing requirements required for the current massive optical signal data. This embodiment realizes the structure of step-by-step light splitting delay of the optical FIR filter by connecting multiple adjustable beam splitters using delay lines. Compared with the structure of first light splitting and then delaying in the prior art, it can reduce the number of unit delay lines, and form the optical path difference with the next adjustable beam splitter through the adjustable beam splitter and the delay line, further shortening the required length of the delay line, thereby reducing the propagation length required for the optical signal data in the optical FIR filter, thereby reducing the transmission loss of the optical signal in the optical FIR filter.

[0106] Embodiment 2

[0107] Please refer to Figure 7 , is a schematic diagram of the steps of a filtering method of an integrated optical FIR filter provided in an embodiment of the present invention, including steps S301 to S304.

[0108] Step S301: inputting a damaged optical signal to the first adjustable beam splitter, controlling the first adjustable beam splitter to split the damaged optical signal to obtain a first optical signal and a third optical signal, and then inputting the third optical signal to the next adjustable beam splitter through a delay line.

[0109] In this embodiment, inputting the damaged optical signal to the first adjustable beam splitter specifically includes:

[0110] Obtaining an effective refractive index of the adjustable beam splitter, a length of the adjustable beam splitter, an effective refractive index of a delay line, and a length of the delay line;

[0111] The sampling interval is determined according to the effective refractive index of the adjustable beam splitter, the length of the adjustable beam splitter, the effective refractive index of the delay line and the length of the delay line:

[0112] Δt=(n effs L s +n effd L d ) / c,

[0113] Where Δt is the sampling interval, n effs is the effective refractive index of the tunable beam splitter, n effd is the effective refractive index of the delay line, L s is the length of the adjustable beam splitter, L d is the length of the delay line, c is the speed of light;

[0114] The damaged optical signal is input to the first adjustable beam splitter according to the sampling interval.

[0115] Step S302: Control the other adjustable beam splitters except the first and the last one to receive the third optical signal output by the previous adjustable beam splitter, and split the third optical signal to obtain the first optical signal, and then input the split third optical signal into the next adjustable beam splitter through the delay line.

[0116] Step S303: when the last adjustable beam splitter receives the third optical signal, control the last adjustable beam splitter to input the third optical signal as the first optical signal into the first phase shifter.

[0117] In this embodiment, controlling the first adjustable beam splitter to split the damaged optical signal to obtain the first optical signal and the third optical signal specifically includes:

[0118] Obtaining a tap amplitude coefficient of the first adjustable beam splitter;

[0119] Normalizing the tap amplitude coefficient according to a preset normalization method, and using the square value of the normalized tap amplitude coefficient as the splitting ratio of the first adjustable beam splitter;

[0120] According to the splitting ratio, the first adjustable beam splitter is controlled to split the damaged optical signal to obtain a first optical signal and a third optical signal.

[0121] It should be noted that the specific process of the preset normalization method, please refer to the description of the tap amplitude coefficient normalization in Example 1, and the process of amplitude regulation, please refer to the description of Example 1, which will not be repeated here. The specific spectroscopic process of step S301 to step S303, please refer to the description of Example 1, which will not be repeated here.

[0122] Step S304: Control the first phase shifter to receive the first optical signal output by the adjustable beam splitter, and perform phase compensation and phase control on the first optical signal to obtain a second optical signal, and then control the beam combiner to synthesize the second optical signal into a restored optical signal to complete filtering of the damaged optical signal.

[0123] In this embodiment, controlling the first phase shifter to receive the first optical signal output by the adjustable beam splitter, and performing phase compensation and phase control on the first optical signal to obtain the second optical signal specifically includes:

[0124] Acquire a tap phase coefficient of each first phase shifter, and determine a phase control value of each first phase shifter according to the tap phase coefficient and in combination with a preset waveguide phase error;

[0125] The first phase shifter is controlled to receive the first optical signal output by the adjustable beam splitter, and phase compensation and phase control are performed on the first optical signal according to the phase control value to obtain a second optical signal.

[0126] It should be noted that for the specific process of phase compensation and phase regulation, please refer to the description in Example 1, and will not be repeated here.

[0127] This embodiment inputs a damaged optical signal to a first adjustable beam splitter, then controls the first adjustable beam splitter to split the damaged optical signal to obtain a first optical signal and a third optical signal, then inputs the third optical signal to a next adjustable beam splitter through a delay line, and then controls the subsequent adjustable beam splitter to split and delay the third optical signal, thereby realizing step-by-step splitting delay. In the form of step-by-step splitting delay, compared with the structure of first splitting and then delaying in the prior art, the number of unit delay lines can be reduced, and an optical path difference with the next adjustable beam splitter is formed together by the adjustable beam splitter and the delay line, further shortening the required length of the delay line, thereby reducing the propagation length required for optical signal data in the optical FIR filter, thereby reducing the transmission loss of the optical signal in the optical FIR filter. This embodiment performs light splitting through an adjustable beam splitter and performs phase compensation and phase control through a first phase shifter, thereby realizing the equivalent function of a digital processing domain FIR filter during the optical signal propagation process. Through the structure of step-by-step light splitting delay and the form of phase control and phase compensation by multiple first phase shifters, it can better adapt to the computing requirements required for the current massive optical signal data.

[0128] In summary, the embodiment of the present invention performs light splitting through multiple adjustable beam splitters, and performs phase compensation and phase control with multiple first phase shifters, thereby realizing the equivalent function of the digital processing domain FIR filter in the process of optical signal propagation. Through the structure of step-by-step light splitting delay, and the form of phase control and phase compensation by multiple first phase shifters, it can better adapt to the computing requirements required for the current massive optical signal data. The present invention realizes the structure of step-by-step light splitting delay of the optical FIR filter by connecting multiple adjustable beam splitters through delay lines. Compared with the structure of first light splitting and then delaying in the prior art, the number of unit delay lines can be reduced, and the optical path difference between the adjustable beam splitter and the next adjustable beam splitter is formed together by the adjustable beam splitter and the delay line, further shortening the required length of the delay line, thereby reducing the propagation length required for the optical signal data in the optical FIR filter, thereby reducing the transmission loss of the optical signal in the optical FIR filter.

[0129] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. An integrated optical FIR filter, comprising: A plurality of delay lines, characterized in that they further comprise: a plurality of adjustable beam splitters, a plurality of first phase shifters and beam combiners connected in sequence; The first adjustable beam splitter is used to receive a damaged optical signal and split the damaged optical signal to obtain a first optical signal and a third optical signal, and then input the third optical signal into the next adjustable beam splitter through the delay line; Except for the first and last adjustable beam splitters, the other adjustable beam splitters are used to receive the third optical signal output by the previous adjustable beam splitter, split the third optical signal to obtain the first optical signal, and then input the split third optical signal into the next adjustable beam splitter through the delay line; When the third optical signal is input to the last adjustable beam splitter, the last adjustable beam splitter inputs the third optical signal as the first optical signal to the first phase shifter; The first phase shifter is used to receive the first optical signal output by the adjustable beam splitter, and perform phase compensation and phase control on the first optical signal to obtain a second optical signal; The beam combiner is used to combine the second optical signal output by the first phase shifter into a restored optical signal; The input end of the first adjustable beam splitter serves as the input port of the integrated optical FIR filter for receiving the damaged optical signal; the output end of the beam combiner serves as the output port of the integrated optical FIR filter for outputting the restored optical signal.

2. An integrated optical FIR filter as claimed in claim 1, characterized in that: The adjustable beam splitter comprises: a first beam splitter, a second phase shifter and a second beam splitter; A first output end of the first beam splitter is connected to an input end of the second phase shifter; The second output end of the first beam splitter is connected to the second input end of the second beam splitter; The output end of the second phase shifter is connected to the first input end of the second beam splitter; The first output end of the second beam splitter is used to output a third optical signal; The second output end of the second beam splitter is used to output the first optical signal; The input end of the first beam splitter of the first adjustable beam splitter is used to receive the damaged optical signal, and the input ends of the first beam splitters of the other adjustable beam splitters are used to receive the third optical signal.

3. An integrated optical FIR filter as claimed in claim 1, characterized in that: When the number of the adjustable beam splitters is an integer power of 2, the beam combiner adopts an MMI beam combiner array; The MMI combiner array comprises a plurality of sequentially connected MMI combiner units; The first MMI combiner unit includes an MMI combiner; the number of MMI combiners in the other MMI combiner units is twice the number of MMI combiners in the previous MMI combiner unit; except for the last MMI combiner unit, each of the MMI combiners in the other MMI combiner units is connected to two MMI combiners in the next MMI combiner unit; When the number of the adjustable beam splitters is not an integer power of 2, the beam combiner adopts an all-in-one MMI beam combiner.

4. An integrated optical FIR filter as claimed in claim 1, characterized in that: The first adjustable beam splitter extracts the first optical signal from the damaged optical signal according to a preset tap amplitude coefficient; except for the first and last adjustable beam splitters, the other adjustable beam splitters extract the first optical signal from the third optical signal according to the preset tap amplitude coefficient; the first phase shifter performs phase compensation and phase control on the first optical signal according to a preset tap phase coefficient.

5. An integrated optical FIR filter as claimed in claim 1, characterized in that: The waveguide length between each of the first phase shifters and the beam combiner is the same.

6. An integrated optical FIR filter as claimed in claim 1, characterized in that: The sampling interval of the integrated optical FIR filter is determined by the adjustable beam splitter and the delay line.

7. A filtering method for an integrated optical FIR filter, characterized in that: An integrated optical FIR filter according to any one of claims 1 to 6, comprising: Inputting a damaged optical signal to the first adjustable beam splitter, controlling the first adjustable beam splitter to split the damaged optical signal to obtain a first optical signal and a third optical signal, and then inputting the third optical signal to the next adjustable beam splitter through a delay line; Controlling the other adjustable beam splitters except the first and the last one to receive the third optical signal output by the previous adjustable beam splitter, and splitting the third optical signal to obtain the first optical signal, and then inputting the split third optical signal into the next adjustable beam splitter through the delay line; When the last adjustable beam splitter receives the third optical signal, controlling the last adjustable beam splitter to input the third optical signal as the first optical signal into the first phase shifter; The first phase shifter is controlled to receive the first optical signal output by the adjustable beam splitter, and phase compensation and phase regulation are performed on the first optical signal to obtain a second optical signal. Then, the beam combiner is controlled to combine the second optical signal into a restored optical signal to complete filtering of the damaged optical signal.

8. The filtering method of an integrated optical FIR filter as claimed in claim 7, characterized in that: The step of inputting a damaged optical signal to the first adjustable beam splitter specifically comprises: Obtaining an effective refractive index of the adjustable beam splitter, a length of the adjustable beam splitter, an effective refractive index of a delay line, and a length of the delay line; The sampling interval is determined according to the effective refractive index of the adjustable beam splitter, the length of the adjustable beam splitter, the effective refractive index of the delay line and the length of the delay line: Δt=(n effs L s +n effd L d ) / c, Where Δt is the sampling interval, n effs is the effective refractive index of the tunable beam splitter, n effd is the effective refractive index of the delay line, L s is the length of the adjustable beam splitter, L d is the length of the delay line, c is the speed of light; The damaged optical signal is input to the first adjustable beam splitter according to the sampling interval.

9. The filtering method of an integrated optical FIR filter as claimed in claim 8, characterized in that: The controlling the first adjustable beam splitter to split the damaged optical signal to obtain the first optical signal and the third optical signal specifically includes: Obtaining a tap amplitude coefficient of the first adjustable beam splitter; Normalizing the tap amplitude coefficient according to a preset normalization method, and using the square value of the normalized tap amplitude coefficient as the splitting ratio of the first adjustable beam splitter; According to the splitting ratio, the first adjustable beam splitter is controlled to split the damaged optical signal to obtain a first optical signal and a third optical signal.

10. The filtering method of an integrated optical FIR filter according to claim 8, characterized in that: The controlling the first phase shifter to receive the first optical signal output by the adjustable beam splitter, and performing phase compensation and phase control on the first optical signal to obtain a second optical signal specifically includes: Acquire a tap phase coefficient of each first phase shifter, and determine a phase control value of each first phase shifter according to the tap phase coefficient and in combination with a preset waveguide phase error; The first phase shifter is controlled to receive the first optical signal output by the adjustable beam splitter, and phase compensation and phase control are performed on the first optical signal according to the phase control value to obtain a second optical signal.

Images