Dense fiber encoding method based on continuous light intensity modulation and fiber grating

Abstract

The application discloses a dense optical fiber coding method based on continuous light intensity modulation and fiber optical grating, which comprises the following steps: emitting C-band or C+L-band continuous light signals by a light source module; dividing the pulse light into different adjustable electro-optic intensity modulators by an optical splitter; modulating the light source in the time domain by each adjustable electro-optic intensity modulator; forming different frequency sinusoidal signals in intensity by different adjustable electro-optic intensity modulators; connecting a multi-port wavelength encoder after each adjustable electro-optic intensity modulator, and the wavelength combinations contained by the light pulses from different ports of the same encoder are different; taking the different frequencies of different light in the time domain as the first coding; taking the different combinations of wavelength components of each code word as the second coding; and the final result of the two codings constitutes the set of all codings. The application solves the technical problems of the prior art, such as the limited real-time coding scale, and cannot meet the use requirements of large-scale networks.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber coding, and particularly relates to a dense optical fiber coding method based on continuous light intensity modulation and fiber gratings. BACKGROUND

[0002] Optical fiber coding is the basis and core technology for realizing digitalization of an all-optical network. Optical fiber link security is the basis for ensuring the security of an optical access network. Studies have shown that about one-third of optical network failures are caused by optical fiber cable failures. Therefore, in order to realize more accurate, reliable, intelligent and efficient digital management of an all-optical network, it is necessary to code each optical fiber link in an optical access network and use the code to monitor the network state. The efficiency of optical fiber coding directly affects the effect of digitalization of an all-optical network. The dense optical fiber coding method based on continuous light intensity modulation and fiber gratings can use fewer wavelength resources to code more links, saving spectrum resources and greatly improving the size of the network that can be monitored by the digitalization technology of an all-optical network in the current situation of tight optical fiber channels and increasing number of users.

[0003] Most of the optical fiber coding technologies currently used only use fiber gratings to perform one-dimensional or two-dimensional wavelength coding on monitoring light pulses. One-dimensional coding can only assign a single wavelength to a link as its unique tag. The advantage of this method is that the structure is simple and easy to implement, and the coder only includes a fiber grating placed at the user end. However, the disadvantages are obvious. The spectrum resources used increase linearly with the number of coded links, and this method can only be used for small-scale optical network coding.

[0004] The commonly used method to increase the number of codes is time-domain multiplexing. In this method, multiple users are divided into groups, and a polling method is used to code the optical fiber links of a certain group of users within a certain period of time. By setting an appropriate polling cycle, each optical fiber link can be effectively coded. The combination of time-domain multiplexing and wavelength coding can simply increase the number of effective codes by using optical switches and control circuits. However, when the number of monitored links is large, the polling window allocated to each group of users also needs to be increased accordingly. In addition, the increase in the number of users also requires more polling groups to meet the demand, which inevitably prolongs the polling cycle and increases the time for which users are not identified and managed, thereby reducing the response efficiency of fault monitoring. The coding technology of the prior art cannot be used to realize real-time coding of large-scale and highly reliable all-optical networks. The real-time coding scale of the prior art is still limited and cannot meet the requirements of large-scale networks. SUMMARY

[0005] The technical problem solved by the present application is to provide a dense optical fiber coding method based on continuous light intensity modulation and fiber grating, so as to solve the technical problems that the coding technology in the prior art cannot be applied to realize real-time coding of large-scale and high-reliability all-optical networks, and the scale of real-time coding in the prior art is still limited and cannot meet the use requirements of large-scale networks.

[0006] The technical solution of the present application is:

[0007] A dense optical fiber coding method based on continuous light intensity modulation and fiber grating, the method comprising:

[0008] Step 1: Emitting a C-band or C+L-band continuous light signal from a light source module, the signal containing more than one light pulse with different center wavelengths but overlapping in time domain;

[0009] Step 2: Dividing the pulse light equally to different adjustable electro-optic intensity modulators by using an optical splitter, each adjustable electro-optic intensity modulator modulating the light source in time domain, different adjustable electro-optic intensity modulators forming different frequency sinusoidal signals in intensity, and the frequency range being MHz order;

[0010] Step 3: Connecting a multi-port wavelength encoder after each adjustable electro-optic intensity modulator, and the wavelengths contained in the light pulses from different ports of the same encoder are different;

[0011] Step 4: Taking different frequencies of different light in time domain as the first coding, and taking different combinations of wavelength components as the second coding for each code word, and the final result of the two codings constitutes the set of all codings.

[0012] When the adjustable electro-optic intensity modulator works in the wavelength range used by the light source, the intensity modulation signal output is a stable frequency sinusoidal signal in time domain, and the output frequency is MHz order, and the output pulse width is 100ns-200ns; the light intensity frequencies formed by different adjustable light intensity modulators have differences in time domain, and n different codings are generated in time domain by n different adjustable electro-optic intensity modulators.

[0013] The multi-port wavelength encoder is composed of more than one 1:2 optical splitter connected step by step, and the two output ports of the upper stage 1:2 optical splitter are connected with the input ports of the two 1:2 optical splitters of the lower stage respectively.

[0014] Only one port of the two output ports of a 1:2 optical splitter is selected to place an optical fiber grating, and each optical fiber grating can completely reflect one wavelength generated by the light source and transmit the remaining wavelengths.

[0015] The fiber grating used in each stage has the same parameter index; the center wavelength should be in the C band range or C+L band, and the reflectivity should be above 99%; the 3dB bandwidth is 0.5nm.

[0016] The multi-port wavelength encoder should reserve at least one wavelength pulse for each port, so that (m-1) wavelengths are used to realize (m-1) codes. 2 Wavelength encoding.

[0017] The continuous optical signal is a broadband light source in the C band with a wavelength range of 1520nm-1570nm, or a broadband light source in the C+L band with a wavelength range of 1520nm-1620nm, and the continuous optical signal has a smooth multi-wavelength continuous optical signal in the wavelength range, and can cover the wavelength range of the fiber grating.

[0018] The continuous optical signal containing m wavelengths and the optical signal modulated with n different intensities together generate n·(m-1) codes. 2 Each code corresponds to a fiber link.

[0019] The beneficial effects of the present application are as follows:

[0020] The present application uses the multi-wavelength continuous light source output as the carrier of the encoding information, and uses the tunable electro-optical modulator to modulate the light source intensity and the fiber grating to encode the light source wavelength twice, so that the encoding of a large number of users can be realized with limited wavelength resources. The C band or C+L band continuous optical signal is emitted from the light source module, the signal contains a plurality of continuous lights with different center wavelengths but overlapping in time domain, then the light source is evenly distributed to a plurality of electro-optical modulators with different frequencies through a splitter, the continuous light passing through the modulator will form sinusoidal signals with different frequencies in time domain, and then the light after the modulator enters an optical fiber grating encoder, the cascaded gratings in the encoder selectively reflect the wavelengths, and form a unique intensity wavelength combination at the output port. The encoders connected after all the modulators have the same structure, and the output ports of the encoders are connected to each fiber link. For a certain link, the wavelength combination type in the wavelength domain and the intensity frequency information of each wavelength of the light source entering the link together constitute the unique encoding information of the link.

[0021] The encoding technology of the prior art cannot be applied to realize real-time encoding of a large-scale and high-reliability all-optical network; the real-time encoding scale of the prior art is still limited, and cannot meet the use requirements of a large-scale network. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A device diagram through which the encoded optical signal is generated and enters the fiber link.

[0023] Figure 2 Spectrum of the light output by the multi-wavelength laser;

[0024] Figure 3 Intensity of the light output by the multi-wavelength laser;

[0025] Figure 4 Intensity of the light after the light pulse passes through the adjustable light intensity modulator;

[0026] Figure 5 Structure diagram of the fiber grating encoder;

[0027] Figure 6 Spectrum of the light after the light passes through the fiber grating encoder;

[0028] Figure 7 Three-dimensional diagram of the time domain, wavelength domain and intensity after the light passes through the fiber grating encoder. DETAILED DESCRIPTION

[0029] In order to improve the number of simultaneously encodable fiber links, the following encoding method is invented: a dense fiber encoding method based on continuous light intensity modulation and fiber gratings, including the following steps:

[0030] (1) A C-band or C+L-band m-wavelength continuous light signal is emitted by the light source module, the signal contains multiple light pulses with different center wavelengths and overlapping in the time domain, and the light intensity remains stable;

[0031] (2) The pulsed light is equally divided into more than ten different adjustable electro-optical intensity modulators using an optical splitter, each adjustable electro-optical intensity modulator modulates the light source in the time domain, and different adjustable electro-optical intensity modulators form different frequency sinusoidal signals in intensity, and the frequency range is in the order of MHz.

[0032] (3) Each light modulator is followed by a 2 m -1 port wavelength encoder, the light pulses from different ports of the same wavelength encoder contain different wavelength combinations.

[0033] (4) The different frequencies of the light of different wavelengths in the time domain are used as the first encoding, and the different combinations of wavelength components in each code word are used as the second encoding, and the final result of the two encodings constitutes the set of all encodings.

[0034] The m-wavelength continuous light source in the above scheme can ensure that there is an m-wavelength continuous light signal with stable emission intensity in the C wavelength or C+L wavelength range, and at the same time ensure that the wavelength range of the fiber grating can be covered.

[0035] The adjustable electro-optical intensity modulator in the above scheme has good intensity modulation effect when working in the wavelength range used by the light source, ensuring that the output intensity modulation signal is a stable frequency sinusoidal signal in the time domain, and the output frequency is in the order of MHz, and the output pulse width is 100ns-200ns; the light intensity frequencies formed by different adjustable light intensity modulators have obvious differences in the time domain, and n different codes can be generated in the time domain by n different light intensity modulators.

[0036] The multi-port wavelength encoder in the above scheme is composed of 2m-1 branch optical splitters connected step by step. The two output ports of the previous stage optical splitter are connected to the input ports of the two splitters of the next stage. Only one port of the two output ports of an optical splitter is selected to place an optical fiber grating. Each optical fiber grating can completely reflect one of the wavelengths generated by the light source and transmit the remaining wavelengths. The optical fiber gratings used in each stage have the same parameter indicators (such as the center wavelength should be in the C band range or C+L band, the reflectivity reaches 99%, and the 3dB bandwidth is about 0.5nm, etc.). Since it is necessary to ensure that there is an optical pulse output, the ports of the encoder should at least reserve a pulse of one wavelength, so that a total of (m-1) 2 wavelength encodings can be achieved using m optical wavelengths.

[0037] In the above scheme, a total of n·(m-1) 2 encodings can be generated using optical pulses containing m wavelengths and n adjustable light intensity modulators, and each encoding can uniquely correspond to an optical fiber link.

[0038] Figure 1 The device diagram for the coded optical signal from generation to entering the optical fiber link. The C band or C+L band optical signal is emitted by the light source module, the signal contains multiple optical pulses with different center wavelengths but overlapping in the time domain, then the optical pulses are evenly distributed to multiple adjustable electro-optical intensity modulators by the splitter. These electro-optical intensity modulators will modulate the light intensity at different frequencies. The light leaving each adjustable electro-optical intensity modulator then enters an optical fiber grating encoder. The cascaded gratings inside the encoder selectively reflect the pulse wavelengths, forming a unique pulse wavelength combination at the output port. All the encoders after the optical frequency comb source have the same structure. The output ports of these encoders are routed to each optical fiber link. For a certain link, the optical pulse entering it in the time domain has a unique encoding information composed of the optical intensity frequency and the wavelength combination type.

[0039] Figure 2 The optical spectrum diagram of the light source output by the multi-wavelength laser. The light source is composed of multiple continuous optical signals with different center wavelengths, and the spacing between adjacent center wavelengths is the same.

[0040] Figure 3 The light intensity diagram of the light source output by the multi-wavelength laser. The light source contains multiple continuous light signals with different central wavelengths, and the light intensity of the light source should remain stable within a time range of 100ns-200ns, so that the light source can be stably output after being modulated by an electro-optical intensity modulator.

[0041] Figure 3 The light intensity diagram of the light signal after passing through the adjustable electro-optical intensity modulator. To ensure that the light signals at each central wavelength are all generated into sinusoidal waves with the same frequency, the adjustable electro-optical intensity modulator should have good stability within the C band or C+L band, and the generated sinusoidal wave frequency is generally in the order of MHz, and the duration is about 100ns-200ns.

[0042] Figure 4 The structure diagram of the fiber grating encoder. The encoder is composed of multiple 1:2 optical splitters connected in stages. The two output ports of the upper stage optical splitter are respectively connected with the input ports of the two splitters of the next stage. Only one port of the two output ports of an optical splitter is selected to place an optical fiber grating. Each optical fiber grating can completely reflect one of the wavelengths generated by the light source and transmit the remaining wavelengths. The optical fiber gratings used in each stage have the same parameter indicators (such as the central wavelength should be in the C band range or C+L band, the reflectivity reaches 99%, and the 3dB bandwidth is about 0.5nm, etc.). Since it is necessary to ensure that there is an optical pulse output, at least one wavelength pulse should be reserved at each port of the encoder. Thus, m kinds of optical wavelengths can be used to achieve (m-1) 2 kinds of wavelength encoding.

[0043] Figure 6 The spectrum diagram of the light signal leaving a certain port of the 6-wavelength fiber grating encoder. The selected wavelengths (λ1, λ3, λ5, λ6) are used as the encoding signals of the output link, and the same light intensity modulation exists in the range of the selected wavelengths (λ1, λ3, λ5, λ6).

[0044] Figure 7 The three-dimensional coordinate diagram of the light signal leaving a certain port of the 6-wavelength fiber grating encoder in the time domain, wavelength domain and intensity. The adjustable electro-optical signal modulates the intensity of the light source output signal into a sinusoidal wave in the time domain, and the same light intensity sinusoidal wave signal modulation exists in the range of the selected wavelengths (λ1, λ3, λ5, λ6). The time domain modulation and wavelength combination are used as the unique encoding information of the output link signal.

[0045] The embodiment of the present application lists the specific implementation process of the dense optical fiber encoding method based on continuous light source intensity modulation and fiber grating. The number of optical wavelengths and the modulation sinusoidal wave frequency of the adjustable electro-optical intensity modulation in the method can be adjusted according to actual conditions.

Claims

1. A dense optical fiber coding method based on continuous light intensity modulation and fiber grating, characterized in that: The method comprises: ​ Step 1, emitting C-band or C+L-band continuous light signals from a light source module, the signals containing more than one light pulse with different center wavelengths but overlapping in time domain; Step 2, using an optical splitter to divide the pulse light into different adjustable electro-optical intensity modulators, each adjustable electro-optical intensity modulator modulating the light source in time domain, and different adjustable electro-optical intensity modulators forming different frequency sinusoidal signals in intensity, with the frequency range being MHz level; Step 3, connecting a multi-port wavelength encoder after each adjustable electro-optical intensity modulator, and the wavelength combinations contained in the light pulses from different ports of the same encoder being different; the multi-port wavelength encoder being composed of more than one 1:2 optical splitter connected step by step, the two output ports of the upper-stage 1:2 optical splitter being connected with the input ports of the two lower-stage 1:2 optical splitters respectively; only one port of the two output ports of one 1:2 optical splitter being selected to place an optical fiber grating, and each optical fiber grating being able to completely reflect one wavelength generated by the light source and transmit the remaining wavelengths. Step 4: Use the different frequencies of different lights in the time domain as the first encoding, and then use different combinations of wavelength components for each codeword as the second encoding. The final result of the two encodings constitutes the set of all codes. Each port of the multi-port wavelength encoder should retain at least one wavelength pulse. Therefore, calculate the total number of pulses achieved using m light wavelengths. Wavelength encoding; a total of m wavelengths of continuous optical signals and n optical signals modulated with different intensities are generated. Each type of code uniquely corresponds to a fiber optic link.

2. The method according to claim 1, wherein the method is based on continuous intensity modulation of light and fiber grating. When the adjustable electro-optical intensity modulators work in the wavelength range used by the light source, the intensity modulation signals outputted are stable frequency sinusoidal signals in time domain, with the output frequency being MHz level and the output pulse width being 100ns-200ns; the light intensity frequencies formed by different adjustable electro-optical intensity modulators are different in time domain, and n different encodings are generated in time domain by n different adjustable electro-optical intensity modulators.

3. The method of claim 1, wherein the method is based on continuous intensity modulation of light and fiber grating. The optical fiber gratings used in each stage have the same parameter index; the center wavelength should be in the C-band range or C+L-band, and the reflectivity should be more than 99%; the 3dB bandwidth should be 0.5nm.

4. The method of claim 1, wherein the method is based on continuous intensity modulation of light and fiber grating. The continuous light signals are C-band broadband light sources with the wavelength range being 1520nm-1570nm, or C+L-band broadband light sources with the wavelength range being 1520nm-1620nm, and the continuous light signals have stable multi-wavelength continuous light signals in the wavelength range, and can cover the wavelength range of the optical fiber grating.

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