CN115173986B

CN115173986B - A Low Crosstalk Wavelength Division Multiplexing System

Info

Publication number: CN115173986B
Application number: CN202210614765.9A
Authority: CN
Inventors: 郑宇�; 黄颖
Original assignee: Wuhan Keyu Zhilian Information Technology Co ltd
Current assignee: Wuhan Keyu Zhilian Information Technology Co ltd
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2024-11-22
Anticipated expiration: 2042-05-30
Also published as: CN115173986A

Abstract

The invention provides a low-crosstalk wavelength division multiplexing system, which comprises a plurality of transmitters, a plurality of modulators, a multiplexer, a demultiplexer, a plurality of groups of dichroic filters and a plurality of receivers, wherein each transmitter is connected with the multiplexer through a corresponding modulator, the multiplexer is connected with the demultiplexer through an optical fiber, and the demultiplexer is respectively connected with the plurality of receivers through a corresponding group of dichroic filters; each group of dichroic filters carries out filtering treatment on each path of different wavelength optical signals separated by the demultiplexer, so that the wavelength ranges of the optical signals of each channel are not overlapped, the crosstalk among a plurality of channels is avoided, and the low-crosstalk wave demultiplexer is realized.

Description

Low crosstalk wavelength division multiplexing system

Technical Field

The present invention relates to the field of optical communications, and more particularly, to a low crosstalk wavelength division multiplexing system.

Background

Wavelength Division Multiplexing (WDM) is a key technology to increase the amount of data transmitted in a single optical fiber by simultaneously transmitting multiple carrier wavelengths with different data streams. Each wavelength is a "channel" of the transmission data stream, which is multiplexed and sent into the optical fiber, where it is demultiplexed at the other end of the fiber after transmission in the fiber.

Typically, WDM systems consist of a plurality of transmitters, a plurality of modulators, a multiplexer, an optical fiber, a demultiplexer and a plurality of receivers. Each transmitter and corresponding modulator is configured to generate a data stream within a particular wavelength range corresponding to a particular wavelength or particular channel, each receiver is configured to receive the data stream corresponding to the particular wavelength or particular channel, and a multiplexer is configured to combine the data stream of each channel into an optical fiber to increase the bandwidth utilization potential, and a demultiplexer is configured to separate the optical signal from the optical fiber into the receiver corresponding to each channel.

In wavelength division multiplexing systems based on silicon photonics, optical crosstalk is a common problem in the demultiplexing process. When a portion of the signal light from one channel is demultiplexed to the corresponding receiver of the other channel, the signals will become noise in the other channel, which is called crosstalk. In optical networks requiring high-speed communications, crosstalk can lead to a decrease in the optical signal-to-noise ratio (SNR), which in turn can lead to an increase in the Bit Error Rate (BER) in the system. While increasing the power of the input signal may increase the osnr, crosstalk between channels still exists.

The wavelength division multiplexing system based on silicon photons can be used for realizing low-cost high-speed optical communication in a data center. High-speed communications require large channel bandwidths and small channel wavelength intervals. There are several methods available for obtaining flat-top spectral outputs based on echelle grating structures for meeting the requirements of large channel bandwidths, such as using multimode interference structures at the input waveguides to produce 'multimode' inputs and multimode outputs at the output waveguides. However, multimode interference structures require high processing accuracy while also increasing insertion loss. In addition, multimode outputs require wider waveguides, increasing the size of the demultiplexing device, while also increasing cross-talk between channels. The large channel bandwidth and small channel wavelength spacing present challenges in developing demultiplexers with low crosstalk. There are some methods to improve the cross-talk of echelle gratings, such as applying thin film filters to address the problem of channel isolation. However, based on the current technology, it is difficult to integrate a thin film filter with a silicon photonic mesa.

Disclosure of Invention

The invention provides a low-crosstalk wavelength division multiplexing system aiming at the technical problems existing in the prior art, which comprises a plurality of transmitters, a plurality of modulators, a multiplexer, a demultiplexer, a plurality of groups of dichroic filters and a plurality of receivers, wherein each transmitter is connected with the multiplexer through a corresponding modulator, the multiplexer is connected with the demultiplexer through an optical fiber, and the demultiplexer is respectively connected with the plurality of receivers through a corresponding group of dichroic filters;

Each of the transmitters and corresponding modulators for generating a data stream within a particular wavelength range corresponding to a particular wavelength or particular channel;

The multiplexer is used for merging the data streams in the specific wavelength range of each channel into an optical fiber and then transmitting the data streams to the demultiplexer;

The demultiplexer is used for separating the optical signals from the optical fibers into a group of dichroic filters corresponding to each channel;

the group of dichroic filters are used for filtering the optical signals in each path of specific wavelength range and transmitting the filtered optical signals to the receivers of the corresponding channels.

On the basis of the technical scheme, the invention can also make the following improvements.

Optionally, each set of dichroic filters includes two cascaded dichroic filters, wherein one dichroic filter is a low pass filter and the other dichroic filter is a high pass filter, each output port of the demultiplexer is connected to an input port of a first dichroic filter of the two cascaded dichroic filters, and an output port of the second dichroic filter is connected to a corresponding receiver.

Optionally, the cut-off wavelength of each corresponding set of dichroic filters is set according to the data stream within the specific wavelength range generated by each of the transmitters and the corresponding modulator, so that the wavelength ranges of the filtered optical signals received by each receiver do not overlap.

Optionally, the setting the cut-off wavelength of each corresponding set of dichroic filters according to the data stream within the specific wavelength range generated by each of the emitters and the corresponding modulator includes:

and setting the cut-off wavelength of the high-pass filter and the cut-off wavelength of the low-pass filter in each group of dichroic filters according to the data flow in the specific wavelength range generated by each transmitter and the corresponding modulator.

Alternatively, the band pass function is achieved by setting the cutoff wavelength of the high pass filter and the cutoff wavelength of the low pass filter in each set of dichroic filters.

According to the low-crosstalk wavelength division multiplexing system provided by the invention, each dichroic filter carries out filtering treatment on the optical signals with different wavelengths separated by the demultiplexer, so that the wavelength ranges of the optical signals of each channel are not overlapped, the crosstalk among a plurality of channels is avoided, and the low-crosstalk wavelength division multiplexing system is realized.

Drawings

Fig. 1 is a schematic structural diagram of a low crosstalk wavelength division multiplexing system according to the present invention;

FIG. 2 is a schematic diagram of a dichroic filter;

FIG. 3 is a schematic diagram of the structure of a dichroic filter;

FIG. 4 is a schematic diagram of an echelle grating demultiplexer;

FIG. 5 is a schematic diagram of a short wavelength light input light guide of a filter;

FIG. 6 is a schematic diagram of a filter for long wavelength light input light guide;

FIG. 7 is a spectral diagram of a filter;

FIG. 8 is a schematic diagram of a filter and demultiplexer cascade;

FIG. 9 is a schematic diagram of the demultiplexer output spectrum;

Fig. 10 is a schematic diagram of a filter and demultiplexer cascade output spectrum.

Detailed Description

The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.

Example 1

Referring to fig. 1, a low crosstalk wavelength division multiplexer includes a plurality of transmitters, a plurality of modulators, a multiplexer, a demultiplexer, a plurality of sets of dichroic filters, and a plurality of receivers, each transmitter being connected to the multiplexer through a corresponding modulator, the multiplexer being connected to the demultiplexer through an optical fiber, the demultiplexer being connected to the plurality of receivers through a corresponding set of dichroic filters, respectively.

Wherein each transmitter and corresponding modulator is configured to generate a data stream within a specific wavelength range corresponding to a specific wavelength or a specific channel; a multiplexer for combining the data streams within a specific wavelength range of each channel into an optical fiber and transmitting to the demultiplexer; a demultiplexer for separating the optical signals from the optical fibers into a set of dichroic filters corresponding to each channel; and the dichroic filters are used for carrying out filtering processing on each path of optical signals in a specific wavelength range and transmitting the optical signals with the filtered wavelengths to the receivers of the corresponding channels.

Referring to fig. 2 and 3, each set of dichroic filters includes two cascaded dichroic filters, one of which is a low pass filter and the other of which is a high pass filter, each output port of the demultiplexer being connected to an input port of a first of the two cascaded dichroic filters and an output port of the second dichroic filter being connected to a corresponding receiver.

To reduce or avoid cross-talk between different channels, the cut-off wavelength of each corresponding set of dichroic filters is set according to the data streams within a specific wavelength range generated by each transmitter and corresponding modulator such that the wavelength ranges of the filtered optical signals received by each receiver do not overlap.

Specifically, according to the data stream within the specific wavelength range generated by each emitter and the corresponding modulator, the cut-off wavelengths of the two dichroic filters in the group are set respectively, that is, the cut-off wavelength of the low-pass filter and the cut-off wavelength of the high-pass filter are set respectively. The low-pass dichroic filter only allows the light signals with short wavelength to pass, the high-pass dichroic filter only allows the light signals with long wavelength to pass, the low-pass dichroic filter and the high-pass dichroic filter realize the filtering of the long wavelength and the short wavelength, the low-pass filter and the high-pass filter cooperate to jointly realize the function of band-pass filtering, and the filtered light signals can be transmitted to corresponding receivers according to requirements.

Channel crosstalk based on echelle grating demultiplexers is reduced by cascading a dichroic filter (as shown in fig. 3) with each output channel of the demultiplexer (as shown in fig. 4). The dichroic filter has an asymmetric structure consisting of a plurality of silicon waveguides and silicon oxide cladding layers, compatible with CMOS fabrication processes. Fig. 5 and 6 show propagation paths of light waves at the time of short wavelength light input and long wavelength light input of the dichroic filter, respectively. As shown in fig. 7, the dichroic filter has a very rapid spectral energy change at the cut-off wavelength, which is advantageous for reducing crosstalk. At the same time, the dichroic filter can adjust the cut-off wavelength by changing the structural parameters. As shown in fig. 8, the demultiplexer separates optical signals within four specific wavelength ranges, and outputs the signals to the receiver through different channels, and since there is an overlap between the specific wavelength ranges of each channel, there is crosstalk between the different channels. Therefore, a group of two dichroic filters is cascaded at each output channel of the demultiplexer, and by setting the cut-off on wavelength of the two dichroic filters in the group, there is no overlap between the wavelength ranges of the optical signals of the four channels filtered by the dichroic filters, so as to avoid crosstalk between the four channels. As shown in fig. 8, by cascading the dichroic filters with the demultiplexer, the excess bandwidth of each channel in the grating-based demultiplexer can be optimized to improve crosstalk. The output spectrum of the echelle grating demultiplexer is shown in fig. 9, with significant crosstalk between channels. After the output of the echelle demultiplexer is cascaded with a dichroic filter, the output spectrum is as shown in fig. 10, and crosstalk between channels is greatly reduced.

The low-crosstalk wavelength division multiplexer provided by the invention can optimize the redundant bandwidth of each channel in the grating-based demultiplexer through cascading the dichroic filter and the demultiplexer, avoid crosstalk among a plurality of channels, realize the low-crosstalk wavelength division multiplexer and have the following advantages:

1. the flat-top spectrum output is realized, and the bandwidth of output signals is increased.

2. The crosstalk between channels is reduced, and the low-crosstalk wave-division multiplexer is realized.

In the foregoing embodiments, the descriptions of the embodiments are focused on, and for those portions of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A low crosstalk wavelength division multiplexing system, characterized in that it comprises a plurality of transmitters, a plurality of modulators, a multiplexer, a demultiplexer, a plurality of groups of dichroic filters and a plurality of receivers, wherein each transmitter is connected to the multiplexer through a corresponding modulator, the multiplexer is connected to the demultiplexer through an optical fiber, and the demultiplexer is connected to a plurality of receivers through a corresponding group of dichroic filters respectively;

Each of the transmitters and the corresponding modulator is used to generate a data stream within a specific wavelength range corresponding to a specific wavelength or a specific channel;

The multiplexer is used to merge the data streams within the specific wavelength range of each channel into the optical fiber and then transmit them to the demultiplexer;

The demultiplexer is used to separate the optical signal from the optical fiber into a set of dichroic filters corresponding to each channel;

The set of dichroic filters is used to filter the optical signals within each specific wavelength range and transmit the filtered optical signals to the receiver of the corresponding channel;

Each set of dichroic filters includes two cascaded dichroic filters, one of which is a low-pass filter and the other is a high-pass filter, each output port of the demultiplexer is connected to the input port of the first dichroic filter in the two cascaded dichroic filters, and the output port of the second dichroic filter is connected to the corresponding receiver;

According to the data stream within the specific wavelength range generated by each of the transmitters and the corresponding modulator, the cutoff wavelength of each corresponding group of dichroic filters is set so that the wavelength ranges of the filtered optical signals received by each receiver do not overlap;

The step of setting the cutoff wavelength of each corresponding group of dichroic filters according to the data stream within the specific wavelength range generated by each transmitter and the corresponding modulator comprises:

According to the data stream within the specific wavelength range generated by each of the transmitters and the corresponding modulator, the cut-off wavelength of the high-pass filter and the cut-off wavelength of the low-pass filter in each group of dichroic filters are set respectively.

2. The low crosstalk wavelength division multiplexing system according to claim 1 is characterized in that by setting the cutoff wavelength of the high-pass filter and the cutoff wavelength of the low-pass filter in each group of dichroic filters, each group of dichroic filters can achieve a bandpass function.