A dense fiber encoding method based on optical switch and weak reflectivity grating string

Abstract

The application discloses a dense optical fiber coding method based on an optical switch and a weak reflectivity grating string, and comprises the following steps: 1, a light source module emits a C-band pulse signal, and the signal contains optical pulses with different central wavelengths and overlapping in a time domain; 2, a weak reflectivity grating string is used to code each node to obtain different wavelength pulse combination types, and the coding signals of different coding nodes on the same link are spaced apart in the time domain; 3, the coding signal is injected into an array waveguide grating through an optical circulator, and is decomposed into more than one single-wavelength pulse signal; 4, a detector array and a collection card are used to carry out photoelectric conversion on the coding pulse signal, and the collected signal is output to an FPGA and an upper computer for processing and display; the problems that the prior art cannot be applied to realize real-time coding of a large-scale and high-reliability all-optical network and that the real-time coding scale is limited and cannot meet the use requirements of a large-scale network are solved.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic coding technology, and particularly relates to a dense fiber optic coding method based on optical switches and weak reflectivity grating strings. Background Technology

[0002] Fiber optic coding is the foundation and core technology for realizing all-optical network digitization. Fiber optic link security is fundamental to ensuring the security of optical access networks. Studies have shown that approximately one-third of optical network failures are caused by fiber optic cable faults. Therefore, digitizing each fiber optic link in the optical access network and using this coding to monitor network status, achieving more accurate, reliable, intelligent, and efficient all-optical network digitization management, is a prerequisite for the efficient and stable operation of the optical access network. The efficiency of fiber optic coding directly affects the effectiveness of all-optical network digitization. Dense fiber optic coding methods based on optical switches and low-reflectivity grating strings can encode more links using fewer wavelength resources, saving spectrum resources. In the current context of limited fiber optic channels and a gradually increasing number of users, this can significantly increase the scale of networks that can be monitored by all-optical network digitization technology.

[0003] Most current fiber optic coding technologies utilize fiber Bragg gratings (FBGs) to encode monitoring optical pulses in one or two dimensions. One-dimensional wavelength coding assigns a single wavelength as a unique tag to each link. Its advantages include simple structure and ease of implementation, with the encoder consisting of only a single FBG located at the user end. However, its disadvantages are obvious: the spectral resources used increase linearly with the number of coded links, limiting its applicability to small-scale optical networks. Two-dimensional wavelength coding uses an optical encoder composed of a FBG and a 1-to-2 optical splitter. The encoder is placed at the central office in the access network, employing centralized coding to reduce user-end complexity and significantly improving coding efficiency compared to one-dimensional coding. However, in practical applications, it is still limited by spectral resources and can only encode a few hundred links.

[0004] Commonly used methods to increase the number of codes primarily involve time-domain multiplexing. Multiple users are grouped together, and a polling method is used. Only the fiber optic links of a specific group of users are coded within a certain time period. By setting an appropriate polling period, each fiber optic link is effectively coded. Combining time-division multiplexing wavelength coding methods can easily increase the number of codes effectively through optical switching and control circuits. However, when monitoring links are long, the polling window allocated to each group of users also needs to be increased accordingly. Furthermore, an increase in the number of users requires polling more groups to meet the demand, which inevitably prolongs the polling period. This increases the time users are not identified and managed, reducing the response efficiency of fault monitoring.

[0005] The targeted coding techniques are not suitable for real-time coding of large-scale, high-reliability all-optical networks. Summary of the Invention

[0006] The technical problem this invention aims to solve is to provide a dense fiber coding method based on optical switches and low-reflectivity grating strings, thereby addressing the limitations of existing technologies in achieving real-time coding for large-scale, high-reliability all-optical networks, and the limited scale of real-time coding to meet the requirements of large-scale network use. The technical solution of this invention is as follows:

[0007] The beneficial effects of this invention are:

[0008] This invention uses multi-wavelength probe light pulses synchronously output from a multi-wavelength pulsed light source as the carrier of encoded information. The light pulses are encoded using optical switches and weakly reflective fiber Bragg gratings, enabling encoding for a large number of users with limited wavelength resources. A C-band pulse signal is emitted from the light source module. The signal contains multiple light pulses with different center wavelengths but overlapping in the time domain. These light pulses then pass through a splitter into different optical links. At each optical node along the link, a series of weakly reflective fiber Bragg gratings is placed, selectively reflecting a portion of the pulse wavelength to form a unique pulse wavelength combination for that optical node. The unreflected pulses and the remaining reflected pulses continue encoding at the next optical node. For a given link, the wavelength combination type in the wavelength domain and the temporal separation of each wavelength constitute its unique encoded information for each optical node.

[0009] It solves the problems that existing technologies cannot be applied to real-time coding for large-scale, high-reliability all-optical networks; and that the limited scale of real-time coding cannot meet the requirements of large-scale network use. Attached Figure Description

[0010] Figure 1 This is a diagram illustrating the overall structure of an encoded optical pulse from its generation to its entry into the optical fiber link and receiving module.

[0011] Figure 2 The spectrum of the optical pulses output by a multi-wavelength laser;

[0012] Figure 3 This is a structural diagram of a weak reflectivity fiber grating string encoder;

[0013] Figure 4 This is a spectrum of light pulses passing through a string of weakly reflective gratings;

[0014] Figure 5 This is a graph showing the intensity of the optical pulses output by a low-reflectivity grating string encoder. Detailed Implementation

[0015] To improve the number of optical nodes that can be encoded simultaneously on a single fiber optic link, the following encoding method has been proposed, including the following steps:

[0016] (1) A C-band pulse signal is emitted from the multi-wavelength pulse light source in the light source module. The signal contains more than 6 light pulses with different center wavelengths but overlapping in the time domain.

[0017] (2) Each node is encoded using a weak reflectivity grating string to obtain reflected pulse signals of different wavelength pulse combination types. The encoded signals of different encoded nodes on the same link have different time intervals.

[0018] (3) The reflected pulse signal is injected into the array waveguide grating through the optical circulator and decomposed into multiple single-wavelength pulse signals.

[0019] (4) A detector array and a 6-port acquisition card are used to perform photoelectric conversion on the encoded pulse signal, and the acquired signal is output to the FPGA and host computer for processing and display.

[0020] The multi-wavelength pulsed light source in the above scheme can be controlled by external signals. At the same time, this laser array generates more than 6 light pulses with the same width, power and period in the time domain, different center wavelengths in the wavelength domain and the same 3dB bandwidth. The center wavelength interval of adjacent light pulses is greater than their bandwidth to ensure that the pulses do not overlap in the wavelength domain. Each pulse leaves the laser at the same time and is combined into a single pulse in the time domain through a coupler built into the light source module.

[0021] The weak reflectivity grating string in the above scheme is composed of several weak reflectivity grating strings connected in series. In order to ensure that each coding node contains an optical pulse signal of at least one wavelength, each grating string contains at least one weak reflectivity grating. In order to ensure that the power of the optical pulse signal is sufficient when passing through all coding nodes, the reflectivity of the weak reflectivity grating must be low enough (1% or less) to reflect part of the optical pulse signal and transmit part of it.

[0022] The multi-port acquisition card and detector array in the above scheme can separate light source signals containing multiple wavelengths in the time domain through arrayed waveguide gratings in the wavelength domain, so that the signal received by each port contains only one wavelength, and is uploaded to the PC through FPGA.

[0023] In the above scheme, to ensure that each coded signal contains a pulse signal of at least one wavelength, a total of 2 pulses containing n wavelengths can be generated on a single optical link. n -1 encoding, each encoding can be uniquely mapped to an encoding node in a fiber optic link.

[0024] Figure 1This is a diagram illustrating the overall structure of the encoded optical pulse from generation to entry into the fiber optic link and receiving module. The light source module emits a C-band pulse signal containing more than six optical pulses with different center wavelengths that overlap in the time domain. These pulses are then selectively reflected back at each encoding node, which is composed of weakly reflective gratings. The reflected pulse signals pass through an optical circulator and enter the receiving module. After being uploaded to the host computer via an FPGA, signal processing yields a unique code for each encoding node.

[0025] Figure 2 This is a spectrum of the optical pulses output by a multi-wavelength laser. An optical pulse is composed of multiple pulses with different center wavelengths, and the spacing between adjacent center wavelengths is the same.

[0026] Figure 3 This is a structural diagram of a weak reflectivity fiber Bragg grating string encoder. This grating string is composed of several weak reflectivity grating strings connected in series. To ensure that each encoding node contains an optical pulse signal of at least one wavelength, each grating string must contain at least one weak reflectivity grating. To ensure sufficient power for the optical pulse signal passing through all encoding nodes, the reflectivity of the weak reflectivity gratings must be low enough to reflect and transmit a portion of the optical pulse signal. To ensure that each encoded signal contains a pulse of at least one wavelength, a total of 2n optical pulses containing n wavelengths can be generated on a single optical link. n -1 encoding, each encoding can be uniquely mapped to an encoding node in a fiber optic link.

[0027] Figure 4 This is a spectrum of the optical pulses output by a weak reflectivity grating string encoder. It lists three encoded signals within a selected wavelength range (λ1, λ2, λ3, λ4), with encoded wavelengths of (λ1, λ2), (λ1, λ3, λ4), and (λ1, λ2, λ3), respectively. Each encoded signal is time-domain separated and contains different wavelengths.

[0028] Figure 5 The figure shows the intensity of the optical pulse output signal from a low-reflectivity grating string encoder. For an optical pulse of a specific wavelength, the transmitted optical pulse signal power attenuates after passing through a grating string containing that wavelength. Taking a reflectivity of 5% as an example, the intensity of the reflected and transmitted signals of an optical pulse signal with wavelength λ1 is shown in the figure.

[0029] The embodiments of this invention illustrate the specific implementation process of a dense fiber coding method based on optical switches and weak reflectivity fiber gratings. The number of optical wavelengths used in this invention method can be adjusted according to actual conditions.

Claims

1. A dense fiber coding method based on optical switches and weak reflectivity grating strings, characterized in that: The method includes: Step 1: The light source module emits a C-band pulse signal, which contains light pulses with different center wavelengths but overlapping in the time domain; Step 2: Encode each node using a weak reflectivity grating string to obtain different wavelength pulse combination types. The encoded signals of different encoded nodes on the same link have different time intervals. Step 3: The encoded signal is injected into the arrayed waveguide grating via an optical circulator and decomposed into pulse signals of one or more single wavelengths; Step 4: Use a detector array and acquisition card to perform photoelectric conversion on the coded pulse signal, and output the acquired signal to the FPGA and host computer for processing and display.

2. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 1, characterized in that: The light source module is a multi-wavelength pulsed light source that is controlled by external signals. At the same time, the total laser array generates one or more light pulses with the same width, power and period in the time domain, different center wavelengths in the wavelength domain, and the same 3dB bandwidth.

3. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 2, characterized in that: The center wavelength interval between adjacent optical pulses is greater than the bandwidth. Each pulse leaves the laser at the same time and is combined into a single pulse in the time domain through a coupler built into the light source module.

4. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 1, characterized in that: A string of weak reflectivity gratings is composed of several strings of weak reflectivity gratings connected in series.

5. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 4, characterized in that: Each string of weak reflectivity gratings contains at least one weak reflectivity grating; the reflectivity of the weak reflectivity grating is no higher than 1%.

6. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 1, characterized in that: The acquisition card is a multi-port acquisition card. The multi-port acquisition card and the detector array separate the light source signals containing multiple wavelengths in the time domain through the arrayed waveguide grating in the wavelength domain, so that the signal received by each port contains only one wavelength, and is uploaded to the PC through the FPGA high-speed acquisition card.

7. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 1, characterized in that: Each coded signal contains a pulse of at least one wavelength. A single optical link using optical pulses of n wavelengths generates a total of 2... n -1 encoding, each encoding uniquely corresponds to an encoding node in a fiber optic link.

8. The dense fiber coding method based on optical switches and weak reflectivity grating strings according to claim 1, characterized in that: An optical pulse is composed of one or more pulses with different center wavelengths. The spacing between adjacent center wavelengths is the same, and the main frequency components of each wavelength do not overlap.

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