Low-frequency control signal transmission method and device, and synchronous data transmission method and system

Abstract

The application discloses a low-frequency control signal transmission method, and belongs to the technical field of optical communication. The method is as follows: a first optical signal generated by a main laser is intensity-modulated by a low-frequency control signal, and the generated modulated optical signal is used as an injection optical signal of a slave laser to make the slave laser in a single-period oscillation state, and the slave laser outputs a second optical signal containing two wavelength components corresponding to high and low levels of the low-frequency control signal respectively; then the second optical signal is amplified by an EDFA, and one of the two wavelength components contained in the amplified second optical signal is filtered out and then transmitted. The application further discloses a low-frequency control signal transmission method and device and a synchronous data transmission method and device. The application makes the signal amplitude input to the EDFA constant by means of optical injection, so that the purpose of suppressing the transient effect of the EDFA is achieved, the transient effect suppression effect is better, and the application is simple and does not need to introduce a new optical wavelength.

Description

Technical Field

[0001] This invention relates to a low-frequency control signal transmission method, belonging to the field of optical communication technology. Background Technology

[0002] Optical communication is a communication method that uses light waves as carriers to transmit information such as voice, data, and images. Long-distance transmission of optical signals is plagued by optical power attenuation. To ensure the normal operation of long-distance optical communication links, optical power amplifiers are typically installed at the transmitting end to amplify the transmitted optical signal power and counteract the power attenuation caused by long transmission distances. Erbium-doped fiber amplifiers (EDFAs) are widely used in various optical communication systems due to their advantages such as high amplification gain, wide gain spectrum, low noise figure, and high gain efficiency. However, due to the millisecond-level transient effects of EDFAs, signal distortion can occur when transmitting low-frequency control signals. Taking a synchronous data transmission system as an example, the system requires both a frequency reference signal and a phase synchronization signal. The frequency reference signal is a high-frequency analog signal, while the phase synchronization signal is a low-frequency (Hz to kHz) control signal. It often needs to be transmitted over long distances and split to multiple remote receiving units, ensuring that each remote receiving unit is correlated with its local frequency reference signal and subject to phase synchronization control from the local signal. With the rapid increase in the number of remote receiving units in distributed array / synchronous systems, local signals require multi-path power splitting. Long-distance transmission and extensive power distribution lead to a significant reduction in optical signal power and a sharp deterioration in the signal-to-noise ratio. Therefore, EDFA (Electronic Power Amplifier) ​​is typically used at the signal transmitting end for optical power amplification. However, due to the transient effects of EDFA, the low-frequency phase synchronization signal experiences severe signal distortion.

[0003] To suppress transient effects in EDFAs, the main existing methods include: suppressing transient effects in erbium-doped fiber amplifiers by controlling the pump power; suppressing transient effects in erbium-doped fiber amplifiers by controlling the input power of the EDFA; and suppressing transient effects in EDFAs using feedforward control methods.

[0004] Existing techniques for controlling pump power to suppress transient effects involve changing the pump power level of the EDFA by controlling the injection current of the pump laser diode, thereby controlling the sudden increase or decrease in the number of particles in the upper energy level of the EDFA and achieving the purpose of suppressing the transient effects of the EDFA [Srivastava AK, Sun Y, Zyskind JL, et al. EDFA transient response to channel loss in WDM transmission system[J]. IEEE Photonics Technology Letters, 1997, 9(3): 386-388.]. The technique of controlling the input power of an EDFA to suppress transient effects in an erbium-doped fiber amplifier (EDFA) involves extracting the output power of the EDFA through feedback, introducing an additional probe laser to ensure a constant total power input to the EDFA, or ensuring consistent power entering the EDFA through an introduced probe laser at the input end, thereby suppressing transient effects [Zyskind JL, Sun Y, Ellson J, et al. Fast-link control protection of surviving channels in multiwavelength optical networks[J]. IEEE Photonics Technology Letters, 1997, 9(12): 1667-1669.]. Feedforward control suppresses transient response by adding a new wavelength to transmit the complementary envelope to ensure a constant signal envelope entering the EDFA, thus suppressing transients [Cho JS, Cho MJ, Won Y H. Feed-forward control of transient gaindynamics of an EDFA for optical burst networks[J]. ETRI journal, 2007, 29(5): 679-681.].

[0005] Suppressing transient response by controlling pump power and total input signal power requires precise control techniques and is a complex process. In schemes that use an additional wavelength to modulate the complementary signal to be transmitted to maintain a constant amplitude of the EDFA input optical signal, the closer the additional wavelength is to the original wavelength, the stronger the suppression of transient effects. However, this inevitably leads to beat frequency signals of similar wavelengths or crosstalk issues, and the limited wavelength in wavelength division multiplexing must also be considered. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a low-frequency control signal transmission method and device. By means of optical injection, the amplitude of the signal input to the EDFA is kept constant, thereby achieving the purpose of suppressing the transient effect of the EDFA. The transient effect suppression effect is better and the implementation is simple, without the need to introduce new optical wavelengths.

[0007] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0008] A method for transmitting low-frequency control signals involves modulating the low-frequency control signal into the optical domain, amplifying it using an EDFA, and then transmitting it. The specific method is as follows:

[0009] The first optical signal generated by the master laser is intensity modulated using the low-frequency control signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. Then, the second optical signal is amplified by EDFA, and one of the two wavelength components contained in the amplified second optical signal is filtered out before transmission.

[0010] A low-frequency control signal transmission device is used to modulate a low-frequency control signal in the optical domain and transmit it after amplification by an EDFA; the device includes:

[0011] The main laser is used to generate the first optical signal;

[0012] An intensity modulator is used to intensity modulate the first optical signal with the low-frequency control signal.

[0013] A laser is used to excite a single-cycle oscillation state by using the modulated optical signal output from the intensity modulator as the injection optical signal, thereby outputting a second optical signal containing two wavelength components that correspond to the high and low levels of the low-frequency control signal, respectively.

[0014] EDFA is used to amplify the second optical signal;

[0015] The optical filtering module is used to filter out one of the two wavelength components contained in the amplified second optical signal before transmission.

[0016] Based on the same inventive concept, the following technical solutions can also be obtained:

[0017] A synchronous data transmission method involves modulating a phase synchronization signal and a reference signal separately in the optical domain, amplifying them using the same EDFA, and then transmitting them through the same optical link. The method is detailed below:

[0018] The first optical signal generated by the master laser is intensity modulated using the phase synchronization signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. At the same time, the third optical signal is intensity modulated using the reference signal to generate a reference modulated optical signal. Then, the second optical signal and the reference modulated optical signal are combined and amplified by the same EDFA. One of the two wavelength components contained in the second optical signal in the amplified combined optical signal is filtered out and transmitted through the same optical link.

[0019] Preferably, the third optical signal has the same wavelength as the first optical signal; firstly, the wavelength component in the second optical signal that has the same wavelength as the first optical signal is filtered out, and then it is combined with the reference modulated optical signal.

[0020] A synchronous data transmission system is provided for modulating a phase synchronization signal and a reference signal in the optical domain, amplifying them through the same EDFA, and transmitting them through the same optical link. The synchronous data transmission system includes: a phase synchronization signal modulation module, used to intensity modulate a first optical signal generated by a master laser with the phase synchronization signal, and using the generated modulated optical signal as an injection optical signal to put the slave laser into a single-cycle oscillation state, and the slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively.

[0021] A reference signal modulation module is used to intensity modulate the third optical signal with the reference signal to generate a reference modulated optical signal.

[0022] An optical coupling module is used to combine the second optical signal with the reference modulated optical signal;

[0023] EDFA is used to amplify the combined optical signal output from the optical coupling module;

[0024] The optical filtering module is used to filter out one of the two wavelength components contained in the second optical signal in the amplified combined optical signal before transmitting it through the same optical link.

[0025] Preferably, the third optical signal has the same wavelength as the first optical signal; the phase synchronization signal modulation module further includes a second filtering module, used to filter out the wavelength component in the second optical signal that has the same wavelength as the first optical signal, and then combine it with the reference modulation optical signal.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] This invention utilizes optical injection technology, taking advantage of the mechanism that semiconductor lasers exhibit different nonlinear dynamic states in response to varying injection light intensities. This results in different resonant wavelengths after redshift of the semiconductor laser. Consequently, the wavelength of the optical signal generated by the semiconductor laser continuously changes while the amplitude remains constant. This prevents transient effects during EDFA amplification, effectively solving the signal distortion problem caused by transient effects when low-frequency control signals are amplified and transmitted via EDFA. This invention eliminates the need for complex feedback control systems and the introduction of new wavelength optical signals, making it widely applicable to EDFA amplification and transmission of various low-frequency control signals. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the structural principle of the first embodiment of the synchronous data transmission system of the present invention;

[0029] Figure 2 This is a schematic diagram illustrating the structural principle of the second embodiment of the synchronous data transmission system of the present invention;

[0030] Figure 3 This is a schematic diagram illustrating the structural principle of the third embodiment of the synchronous data transmission system of the present invention. Detailed Implementation

[0031] To achieve transient suppression in EDFA, the present invention employs optical injection technology. When the semiconductor laser is in a single-cycle oscillation state, the phenomenon that the resonant wavelength of the laser after redshift is caused by different injection light intensities results in continuous wavelength changes while the amplitude remains constant. This prevents transient effects from occurring during EDFA amplification, effectively solving the signal distortion problem caused by transient effects when low-frequency control signals are amplified and transmitted via EDFA.

[0032] The present invention specifically adopts the following technical solution:

[0033] A method for transmitting low-frequency control signals involves modulating the low-frequency control signal into the optical domain, amplifying it using an EDFA, and then transmitting it. The specific method is as follows:

[0034] The first optical signal generated by the master laser is intensity modulated using the low-frequency control signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. Then, the second optical signal is amplified by EDFA, and one of the two wavelength components contained in the amplified second optical signal is filtered out before transmission.

[0035] A low-frequency control signal transmission device is used to modulate a low-frequency control signal in the optical domain and transmit it after amplification by an EDFA; the device includes:

[0036] The main laser is used to generate the first optical signal;

[0037] An intensity modulator is used to intensity modulate the first optical signal with the low-frequency control signal.

[0038] A laser is used to excite a single-cycle oscillation state by using the modulated optical signal output from the intensity modulator as the injection optical signal, thereby outputting a second optical signal containing two wavelength components that correspond to the high and low levels of the low-frequency control signal, respectively.

[0039] EDFA is used to amplify the second optical signal;

[0040] The optical filtering module is used to filter out one of the two wavelength components contained in the amplified second optical signal before transmission.

[0041] Based on the same inventive concept, the following technical solutions can also be obtained:

[0042] A synchronous data transmission method involves modulating a phase synchronization signal and a reference signal separately in the optical domain, amplifying them using the same EDFA, and then transmitting them through the same optical link. The method is detailed below:

[0043] The first optical signal generated by the master laser is intensity modulated using the phase synchronization signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. At the same time, the third optical signal is intensity modulated using the reference signal to generate a reference modulated optical signal. Then, the second optical signal and the reference modulated optical signal are combined and amplified by the same EDFA. One of the two wavelength components contained in the second optical signal in the amplified combined optical signal is filtered out and transmitted through the same optical link.

[0044] In synchronous data transmission systems, two beam split signals of the same optical carrier are often used to modulate the phase synchronization signal and the reference signal respectively. To this end, the present invention further proposes the following preferred solution: the third optical signal has the same wavelength as the first optical signal; firstly, the wavelength component in the second optical signal that has the same wavelength as the first optical signal is filtered out, and then it is combined with the reference modulation optical signal.

[0045] A synchronous data transmission system is provided for modulating a phase synchronization signal and a reference signal in the optical domain, amplifying them through the same EDFA, and transmitting them through the same optical link. The synchronous data transmission system includes: a phase synchronization signal modulation module, used to intensity modulate a first optical signal generated by a master laser with the phase synchronization signal, and using the generated modulated optical signal as an injection optical signal to put the slave laser into a single-cycle oscillation state, and the slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively.

[0046] A reference signal modulation module is used to intensity modulate the third optical signal with the reference signal to generate a reference modulated optical signal.

[0047] An optical coupling module is used to combine the second optical signal with the reference modulated optical signal;

[0048] EDFA is used to amplify the combined optical signal output from the optical coupling module;

[0049] The optical filtering module is used to filter out one of the two wavelength components contained in the second optical signal in the amplified combined optical signal before transmitting it through the same optical link.

[0050] In synchronous data transmission systems, two beam split signals of the same optical carrier are often used to modulate the phase synchronization signal and the reference signal respectively. To this end, the present invention further proposes the following preferred solution: the third optical signal has the same wavelength as the first optical signal; the phase synchronization signal modulation module further includes a second filtering module, which is used to filter out the wavelength component in the second optical signal that has the same wavelength as the first optical signal, and then combine it with the reference modulation optical signal.

[0051] To facilitate public understanding, the technical solution of the present invention will be described in detail below using a multi-channel synchronous data transmission system as an example, in conjunction with the accompanying drawings:

[0052] Figure 1 The basic structure and principle of the first embodiment of the synchronous data transmission system of the present invention are shown, as follows: Figure 1As shown, at the transmitting end, the optical signal with wavelength λ3 emitted by the master laser ML is split into two paths, which are modulated by intensity modulators AM1 and AM2 with a phase synchronization signal and a reference signal, respectively. The modulated optical signal of the phase synchronization signal is injected into the slave laser SL as the injection optical signal, exciting the slave laser into a single-cycle oscillation state. The injection light intensity is controlled by the phase synchronization signal, thereby causing the slave laser to generate different wavelength signals under different phase synchronization signal levels. At this time, the resonant wavelength of the slave laser continuously changes between λ1 and λ2 with the change of the phase synchronization signal level. Specifically, the optical signal output by the slave laser contains a wavelength component with wavelength λ3 and two wavelength components λ1 and λ2 corresponding to the low and high levels of the phase synchronization signal, respectively. Since the wavelength generated by the slave laser increases with the increase of injection intensity, the relationship between wavelengths λ1 and λ2 is... The system is λ2 > λ1, where the wavelength component of λ2 is generated when the phase synchronization signal is at a high level, and the wavelength component of λ1 is generated when the phase synchronization signal is at a low level. To avoid interference between the λ3 wavelength component output from the laser and the reference modulated optical signal with a carrier of λ3, an optical filter OF1 is first used to filter out the λ3 wavelength component from the laser output optical signal. Then, this signal is combined with the reference modulated optical signal and amplified by an EDFA. The combined optical signal contains the λ3 wavelength component modulated by the reference signal, as well as the λ1 and λ2 wavelength components generated from the laser. While some wavelengths of the optical signal input to the EDFA change, the amplitude remains constant, thus preventing transient effects in the EDFA. An optical filter OF2 is used to filter out the λ1 wavelength component from the amplified optical signal, which is then transmitted to the receiving end via a long optical fiber. At the receiving end, the transmitted optical signal is split into multiple paths and input to photodetectors for envelope detection. The detected electrical signals are input to the signal extraction unit, allowing simultaneous acquisition of the phase synchronization signal and the reference signal.

[0053] Figure 2 The basic structure and principle of the second embodiment of the synchronous data transmission system of the present invention are shown, as follows: Figure 2As shown, at the transmitting end, the optical signal with wavelength λ3 emitted by the master laser ML is modulated with a phase synchronization signal by the intensity modulator AM1. The modulated optical signal of the phase synchronization signal is injected into the slave laser SL as the injection optical signal, exciting the slave laser into a single-cycle oscillation state. The injection light intensity is controlled by the phase synchronization signal, thereby causing the slave laser to generate different wavelength signals under different phase synchronization signal levels. At this time, the resonant wavelength of the slave laser continuously changes between λ1 and λ2 with the change of the phase synchronization signal level. Specifically, the optical signal output by the slave laser contains a wavelength component with wavelength λ3 and two wavelength components λ1 and λ2 corresponding to the low and high levels of the phase synchronization signal, respectively. Since the wavelength generated by the slave laser increases with the increase of injection intensity, the relationship between wavelengths λ1 and λ2 is λ2 The wavelength component of λ2 is generated when the phase synchronization signal is at a high level, and the wavelength component of λ1 is generated when the phase synchronization signal is at a low level. The reference signal is modulated by the intensity modulator AM2 onto the optical signal with wavelength λ4 emitted by the laser LD, satisfying the relationship λ4>λ2>λ1>λ3. Since λ4 and λ3 are different, it is not necessary to filter out the wavelength component of λ3 in the optical signal output from the laser. Instead, the optical signal output from the laser and the reference modulated optical signal are directly combined and input into the EDFA. Similarly, some wavelengths of the optical signal input into the EDFA change, but the amplitude remains constant, so the transient effect of the EDFA will not occur. The wavelength component of λ1 in the amplified optical signal of the EDFA is filtered out by the optical filter OF, and then transmitted to the receiving end through a long optical fiber. At the receiving end, the transmitted optical signal is split into multiple paths and input into photodetectors for envelope detection. The detected electrical signals are input into the signal extraction unit, from which the phase synchronization signal and the reference signal can be obtained simultaneously.

[0054] Figure 3 This illustrates the basic structure and principle of the third embodiment of the synchronous data transmission system of the present invention, whose overall structure is similar to... Figure 1 They are basically the same, except that the optical filter OF2 filters out the λ2 wavelength component in the optical signal amplified by the EDFA. Since the remaining λ1 wavelength component corresponds to the low-level control state of the phase synchronization signal, the phase synchronization signal obtained after envelope detection by the photodetector at the receiving end is out of phase with the phase synchronization signal input at the transmitting end. The original input phase synchronization signal can be recovered by inverting it.

Claims

1. A method for transmitting low-frequency control signals, wherein the low-frequency control signal is modulated in the optical domain and amplified by an EDFA before transmission; characterized in that, The method is as follows: The first optical signal generated by the master laser is intensity modulated using the low-frequency control signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. Then, the second optical signal is amplified by EDFA, and one of the two wavelength components contained in the amplified second optical signal is filtered out before transmission.

2. A low-frequency control signal transmission device, used to modulate a low-frequency control signal in the optical domain and transmit it after amplification by an EDFA; characterized in that, The device includes: The main laser is used to generate the first optical signal; An intensity modulator is used to intensity modulate the first optical signal with the low-frequency control signal. A laser is used to excite a single-cycle oscillation state by using the modulated optical signal output from the intensity modulator as the injection optical signal, thereby outputting a second optical signal containing two wavelength components that correspond to the high and low levels of the low-frequency control signal, respectively. EDFA is used to amplify the second optical signal; The optical filtering module is used to filter out one of the two wavelength components contained in the amplified second optical signal before transmission.

3. A method for synchronous data transmission, wherein a phase synchronization signal and a reference signal are modulated into the optical domain respectively, amplified by the same EDFA, and transmitted through the same optical link; characterized in that, The method is as follows: The first optical signal generated by the master laser is intensity modulated using the phase synchronization signal, and the generated modulated optical signal is used as the injection optical signal of the slave laser to put the slave laser into a single-cycle oscillation state. The slave laser outputs a second optical signal containing two wavelength components corresponding to the high and low levels of the low-frequency control signal, respectively. At the same time, the third optical signal is intensity modulated using the reference signal to generate a reference modulated optical signal. Then, the second optical signal and the reference modulated optical signal are combined and amplified by the same EDFA. One of the two wavelength components contained in the second optical signal in the amplified combined optical signal is filtered out and transmitted through the same optical link.

4. The synchronous data transmission method as described in claim 3, characterized in that, The third optical signal has the same wavelength as the first optical signal; firstly, the wavelength component in the second optical signal that has the same wavelength as the first optical signal is filtered out, and then it is combined with the reference modulated optical signal.

5. A synchronous data transmission system, used to modulate a phase synchronization signal and a reference signal into the optical domain respectively, amplify them through the same EDFA, and transmit them through the same optical link; characterized in that, The synchronous data transmission system includes: The phase synchronization signal modulation module is used to intensity modulate the first optical signal generated by the master laser with the phase synchronization signal, and use the generated modulated optical signal as the injection optical signal of the slave laser to make the slave laser in a single-cycle oscillation state, and output a second optical signal containing two wavelength components corresponding to the high and low levels of the low frequency control signal respectively. A reference signal modulation module is used to intensity modulate the third optical signal with the reference signal to generate a reference modulated optical signal. An optical coupling module is used to combine the second optical signal with the reference modulated optical signal; EDFA is used to amplify the combined optical signal output from the optical coupling module; The optical filtering module is used to filter out one of the two wavelength components contained in the second optical signal in the amplified combined optical signal before transmitting it through the same optical link.

6. The synchronous data transmission system as described in claim 5, characterized in that, The third optical signal has the same wavelength as the first optical signal; the phase synchronization signal modulation module further includes a second filtering module, which is used to filter out the wavelength component in the second optical signal that has the same wavelength as the first optical signal, and then combine it with the reference modulation optical signal.

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