A fiber optic hydrophone array remote transmission system and method

Abstract

The application discloses a kind of optical fiber hydrophone array remote transmission system and method, system includes the optical emission module of dry end, optical receiving module, Raman pumping unit and state management unit, and the relay amplifier and optical fiber hydrophone array of wet end;Optical emission module is amplified to power pre-emphasis downlink multi-wavelength laser pulse power;Optical receiving module restores sound field information to uplink multi-wavelength interference optical signal;Relay amplifier is amplified after input optical fiber hydrophone array to downlink multi-wavelength laser pulse, uplink multi-wavelength interference optical signal is amplified after input optical receiving module;Raman pumping unit outputs multi-wavelength Raman pump light, and the uplink multi-wavelength interference optical signal of relay amplifier output is carried out reverse distributed fiber Raman amplification;State management unit is configured different wavelength Raman pump laser power for Raman pumping unit;Optical fiber hydrophone array receives downlink multi-wavelength laser pulse, and outputs multi-wavelength interference optical signal carrying sound field information.

Description

Technical Field

[0001] This invention relates to the field of fiber optic hydrophone technology, specifically a remote transmission system and method for fiber optic hydrophone arrays. Background Technology

[0002] Sound waves are currently the only known form of energy radiation capable of long-range propagation in the ocean. Fiber optic hydrophones are underwater acoustic sensors that use optical fibers as the transmission and sensing medium and utilize sound waves propagating in the ocean to sense, locate, and identify targets. Seafloor fixed array systems are one of the important application forms of fiber optic hydrophone arrays. In recent years, seafloor fixed array systems have gradually expanded from nearshore to deep-sea areas. Furthermore, with the continuous improvement of underwater target vibration reduction and noise reduction technologies, and the increasing demands for detection distance and accuracy, the scale of fiber optic hydrophone arrays in seafloor fixed array systems has been continuously expanding. The number of sensors in a single fiber optic hydrophone array has increased from tens to hundreds, and the offshore transmission distance has also increased from tens of kilometers to hundreds of kilometers.

[0003] Fiber optic hydrophone arrays typically employ wavelength division multiplexing (WDM), time division multiplexing (TDM), and space division multiplexing (SDM) array configurations. As submarine fixed array systems expand into deeper waters, the preferred approach is to increase WDM, followed by TDM, and finally SDM to scale up the fiber optic hydrophone array. Increasing TDM reduces the duty cycle of the interrogation pulses in the optical transmitting unit, hindering the increase of input optical power, and exacerbates noise aliasing during demodulation in the optical receiving unit. Increasing SDM significantly increases system complexity and cost. Introducing coarse WDM multiplexing devices can greatly reduce the optical losses introduced by increasing WDM in the fiber optic hydrophone array, minimizing the impact on the system. However, increasing WDM means a larger optical bandwidth, making it difficult to control the gain flatness of the optical amplification and affecting the consistency of wavelength channel performance.

[0004] Taking a 256-element fiber optic hydrophone array with single-space-division multiplexing as an example, if a 32-wavelength-division × 8-time-division multiplexing method is used, with a wavelength channel spacing of 0.8 nm, the system optical bandwidth is around 25 nm, and the system optical loss is around 30 dB. When the offshore optical transmission distance of the submarine fixed array system exceeds 150 km, even using G.654.D fiber with an attenuation coefficient of 0.152 dB / km, the system optical loss will exceed 75 dB. If aging and maintenance throughout the entire life cycle are further considered, the system optical loss will increase even further.

[0005] Traditionally, repeaterless transmission systems based on distributed Raman optical amplification and remote pump optical amplification technologies support optical losses of approximately 60dB to 70dB. Furthermore, remote pump optical amplification technology is limited by stimulated Raman scattering of the pump light and its transmission attenuation, resulting in limitations in amplification distance and performance. Consequently, it cannot meet the requirements for long-distance broadband optical transmission of dense wavelength division multiplexing fiber optic hydrophone arrays more than 150km offshore.

[0006] To ensure the detection capability of the seabed fixed array system for weak acoustic signals, it is necessary to effectively equalize and amplify the long-distance transmitted broadband analog optical signals. Therefore, a transmission system is needed that can achieve long-distance, high-gain, low-noise optical amplification of broadband analog optical signals, overcoming the limitations of traditional optical amplification methods in terms of transmission distance, while also controlling the gain flatness during the amplification process to ensure the consistency of wavelength channel performance. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and to propose a remote transmission system and method for fiber optic hydrophone arrays.

[0008] To achieve the above objectives, this invention proposes a long-range transmission system for fiber optic hydrophone arrays, used for long-range broadband optical transmission of fiber optic hydrophone arrays more than 150km offshore. The system includes: a dry end optical transmitting module, an optical receiving module, a Raman pumping unit, and a status management unit, and a wet end repeater amplifier and a fiber optic hydrophone array. The optical transmitting module is used to amplify the power of the pre-emphasized downlink multi-wavelength laser pulses before transmitting them through the transmission optical fiber. Input repeater amplifier; The optical receiving module is used to receive light transmitted through the optical fiber. The input uplink multi-wavelength interference optical signal is pre-amplified and processed to restore the sound field information; The relay amplifier is used to transmit the signal via optical fiber. The input downlink multi-wavelength laser pulses are then remotely amplified by high-gain, low-noise optical amplification and transmitted via optical fiber. Input fiber optic hydrophone array; also used for the transmission of fiber optic cables. The input uplink multi-wavelength interference optical signal is remotely amplified by high gain and low noise before being transmitted through optical fiber. To the optical receiver module; The Raman pumping unit is connected to the transmission optical fiber. Optical coupling connection, outputting multi-wavelength Raman pump light, used in transmission optical fibers The uplink multi-wavelength interference optical signal output from the relay amplifier is subjected to reverse distributed fiber Raman amplification to improve gain flatness; The status management unit is connected to the optical emission module, optical receiving module, and Raman pumping unit. It is used to configure different wavelength Raman pumping laser powers for the Raman pumping unit and to monitor the operating status of the system. The fiber optic hydrophone array is used to receive signals transmitted via optical fiber. The input downlink multi-wavelength laser pulses are also used to output multi-wavelength interference light signals carrying acoustic field information to the transmission optical fiber. .

[0009] Preferably, the relay amplifier includes a downlink amplification unit and an uplink amplification unit.

[0010] Preferably, the optical emitting module includes an optical emitting unit and a power amplifier; wherein, The optical emitting unit is used to output multi-wavelength laser pulses with pre-emphasized power; The input terminal of the power amplifier is optically connected to the output terminal of the optical emitting unit, and the output terminal of the power amplifier is connected via a transmission optical fiber. Connected to the input of the downlink amplification unit in a repeater amplifier, it is used to amplify the power of pre-emphasized multi-wavelength laser pulses and inject them into the transmission fiber. .

[0011] Preferably, the optical receiving module includes: a preamplifier and an optical receiving unit, wherein, The output of the preamplifier is optically connected to the input of the optical receiving unit, and the input of the preamplifier is connected to the transmission optical fiber. It is connected to the output of the uplink amplifier unit in the repeater amplifier to improve the receiving sensitivity of the optical receiver unit; The optical receiving unit is used to perform wavelength division multiplexing, optical power adjustment, photoelectric conversion, analog-to-digital conversion and digital demodulation of multi-wavelength interference optical signals, and to restore the sound field information.

[0012] Preferably, the system further includes a remote power supply unit, via an electrical conductor. Connected to a relay amplifier and via a signal connection to a status management unit, the remote power supply unit is a high-voltage constant current source used to achieve remote power supply.

[0013] Preferably, the transmission optical fiber Fiber optic transmission Fiber optic transmission Fiber optic transmission and electrical conductors All are integrated into the submarine optical cable, including the transmission optical fiber. Fiber optic transmission Fiber optic transmission and transmission fiber To achieve optical transmission, G.654.C or G.654.D optical fiber is used; electrical conductors are also required. To achieve electrical transmission.

[0014] Preferably, the transmission optical fiber and transmission fiber The transmission optical fibers are of equal length. and transmission fiber The lengths of the optical fibers are equal; and the transmission optical fibers are... and transmission fiber The sum of the lengths of the transmission optical fiber and transmission fiber The sum of their lengths is equal.

[0015] Preferably, the power amplifier, preamplifier, and repeater amplifier are erbium-doped fiber amplifiers, ytterbium-erbium co-doped fiber amplifiers, or other types of doped medium optical amplifiers.

[0016] On the other hand, the present invention proposes a remote transmission method, which is implemented by a remote transmission system for fiber optic hydrophone arrays as described above.

[0017] Compared with the prior art, the advantages of the present invention are: 1. This invention applies low-loss optical fiber technology to reduce the loss of long-distance optical fibers and extend the system transmission distance; 2. This invention applies remote relay optical amplification technology to achieve remote high-gain low-noise amplification of downlink multi-wavelength laser pulses and uplink multi-wavelength interference optical signals, compensating for the loss of remote transmission optical fibers and fiber hydrophone arrays, and breaking through the limitations of traditional optical amplification methods in terms of transmission distance. 3. This invention applies fiber-optic distributed Raman amplification technology to perform distributed Raman amplification of multi-wavelength interference optical signals in the transmission optical fiber. By adjusting the Raman pump laser power of each wavelength to optimize the gain flatness of the broadband analog optical signal amplification system, the consistency of wavelength channel performance is ensured while improving the quality of the received interference optical signal, enhancing the detection capability of weak underwater acoustic signals, and significantly extending the transmission distance of the seabed fixed array system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the fiber optic hydrophone array remote transmission system in Embodiment 1 of the present invention; Figure 2 This is a simulation diagram of the optical signal-to-noise ratio at the receiver of the 200km transmission system in Embodiment 1 of the present invention. Detailed Implementation

[0019] To address the limitations of traditional repeaterless submarine fixed array systems in terms of transmission distance and the issues of gain flattening control during broadband analog optical signal amplification, this invention provides a remote transmission system for fiber optic hydrophone arrays. By combining dry-end reverse distributed Raman optical amplification technology, wet-end single-stage remote repeater optical amplification technology, and low-loss transmission fiber technology, this system solves the needs for remote transmission of large-scale dense wavelength division multiplexing fiber optic hydrophone arrays and balanced amplification of broadband analog optical signals more than 150km offshore.

[0020] The fiber optic hydrophone array remote transmission system provided by this invention comprehensively utilizes fiber optic distributed Raman optical amplification technology, remote relay optical amplification technology, and low-loss transmission fiber optic technology.

[0021] The remote transmission system comprises an optical transmitting unit, a power amplifier, a remote power supply unit, an optical receiving unit, a Raman pumping unit, a preamplifier, and a status management unit at the dry end, and a repeater amplifier and a fiber optic hydrophone array at the wet end.

[0022] The optical emitting unit is used to output multi-wavelength laser pulses with pre-emphasized power.

[0023] The power amplifier is connected to the output optical fiber of the optical emitting unit and is transmitted through the optical fiber. Connected to the input of the downlink amplification unit in a repeater amplifier, it is used to amplify the power of pre-emphasized multi-wavelength laser pulses and inject them into the transmission fiber. .

[0024] The output of the downlink amplifier unit in the relay amplifier is connected to the input of the fiber optic hydrophone array via a transmission fiber. Connection, used for transmitting optical fiber The transmitted multi-wavelength laser pulses are then subjected to remote high-gain, low-noise optical amplification.

[0025] The input of the uplink amplifier unit in the relay amplifier is connected to the output of the fiber optic hydrophone array via a transmission optical fiber. Connect, and transmit via optical fiber Connected to the input of the preamplifier, it is used to output the fiber optic hydrophone array and transmit it via optical fiber. The transmitted multi-wavelength interference optical signal is then subjected to remote high-gain, low-noise optical amplification.

[0026] The output of the preamplifier is connected to the optical fiber of the optical receiving unit to improve the receiving sensitivity of the optical receiving unit.

[0027] The optical receiving unit is used to perform wavelength division multiplexing, optical power adjustment, photoelectric conversion, analog-to-digital conversion and digital demodulation of multi-wavelength interference optical signals, and to restore the sound field information.

[0028] The Raman pump unit and the transmission optical fiber at the input of the preamplifier Optical coupling connection, outputting multi-wavelength Raman pump light, used in transmission optical fibers The multi-wavelength interference optical signal output from the uplink amplification unit in the relay amplifier is subjected to reverse distributed fiber Raman amplification.

[0029] The remote power supply unit is connected via an electrical conductor. It is connected to the relay amplifier for remote power supply to the relay amplifier.

[0030] The status management unit is signal-connected to the optical transmitting unit, the power amplifier, the remote power supply unit, the Raman pumping unit, the preamplifier, and the optical receiving unit for parameter configuration and operational status monitoring.

[0031] The transmission optical fiber The transmission optical fiber The transmission optical fiber The transmission optical fiber and the electrical conductor Integrated into submarine optical cables, wherein the transmission optical fiber The transmission optical fiber The transmission optical fiber and the transmission optical fiber To achieve optical transmission, the electrical conductor To achieve electrical transmission.

[0032] The transmission optical fiber and the transmission optical fiber The transmission optical fibers are of equal length. and the transmission optical fiber They are of equal length.

[0033] The transmission optical fiber and the transmission optical fiber The sum of the lengths of the transmission optical fiber and the transmission optical fiber The sum of their lengths is equal.

[0034] The transmission optical fiber The transmission optical fiber The transmission optical fiber and the transmission optical fiber It is either G.654.C or G.654.D fiber.

[0035] The Raman pumping unit can independently configure the Raman pump laser power of each wavelength through the state management unit, adjust the gain spectrum of the reverse fiber distributed Raman amplification, and optimize the gain flatness of the system's broadband analog optical signal amplification.

[0036] The power amplifier, the preamplifier, and the repeater amplifier are erbium-doped fiber amplifiers or ytterbium-erbium co-doped fiber amplifiers.

[0037] The remote power supply unit is a high-voltage constant current source.

[0038] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0039] Example 1 Embodiment 1 of the present invention proposes a remote transmission system for fiber optic hydrophone arrays, such as... Figure 1 As shown. The remote transmission system includes an optical transmitting unit, power amplifier, remote power supply unit, optical receiving unit, Raman pump unit, preamplifier, and status management unit at the dry end, and a repeater amplifier and fiber optic hydrophone array at the wet end.

[0040] The multi-wavelength laser pulses, pre-emphasized by the output power of the optical transmitting unit, are amplified by a power amplifier and then injected into the transmission fiber. The output optical power of the power amplifier can be configured via the status management unit to adapt to submarine fixed array systems with different transmission distances or to compensate for optical losses introduced by aging and maintenance of submarine optical cables.

[0041] The downlink amplification unit in the repeater amplifier connects to the transmission fiber. The transmitted multi-wavelength laser pulses are amplified with high gain and low noise to compensate the transmission fiber. Loss, then transmitted through optical fiber Enter the fiber optic hydrophone array.

[0042] The fiber optic hydrophone array outputs a multi-wavelength interference optical signal carrying acoustic field information, which is transmitted through optical fiber. After transmission, the signal enters the uplink amplification unit of the repeater amplifier, where the multi-wavelength interference optical signal is amplified with high gain and low noise to compensate for the fiber optic hydrophone array and transmission fiber. and loss.

[0043] The remote power supply unit provides high-voltage constant current power to the relay amplifier.

[0044] The Raman pump unit outputs multi-wavelength Raman pump light, which performs reverse distributed Raman amplification on the multi-wavelength interference light signal output from the uplink repeater amplifier. Specifically, the multi-wavelength Raman pump light output by the Raman pump unit is used in the transmission optical fiber... The multi-wavelength interference optical signal output from the upstream repeater amplifier is transmitted in the opposite direction and subjected to reverse distributed Raman amplification.

[0045] For example, the Raman pump laser power of each wavelength can be independently configured through the status management unit according to the system conditions, the gain spectrum of the reverse fiber distributed Raman amplification can be adjusted, the gain flatness of the broadband optical signal amplification of the system can be optimized, and the performance consistency of each wavelength channel of the interference signal light can be guaranteed.

[0046] The interference signal light from the reverse distributed Raman optical amplification is further boosted by a preamplifier before entering the optical receiving unit, thus improving its receiving sensitivity. The output optical power of the preamplifier can be configured via a state management unit to adapt to systems with different transmission distances.

[0047] The optical receiving unit realizes the demultiplexing, optical power adjustment, photoelectric conversion, analog-to-digital conversion and digital demodulation of multi-wavelength interference optical signals, and restores the sound field information.

[0048] For example, the power amplifier, preamplifier, and repeater amplifier are typically erbium-doped fiber amplifiers or ytterbium-erbium co-doped fiber amplifiers, but other types of doped optical amplifiers may also be selected.

[0049] For example, transmission optical fiber Fiber optic transmission Fiber optic transmission and transmission fiber Low-loss G.654.C fiber or large-effective-area low-loss G.654.D fiber can be used. Traditional submarine fixed array systems typically use fiber with an effective core area of ​​approximately The attenuation coefficient is approximately Compared to G.652.D fiber, G.654.C fiber has a similar effective core area and a lower attenuation coefficient, reaching approximately [missing value]. This allows for longer transmission distances; G.654.D fiber has a larger effective core area and a lower attenuation coefficient, with a maximum effective core area of ​​approximately [missing information]. The attenuation coefficient can reach approximately It can support higher fiber optic power and longer transmission distance.

[0050] For example, when the transmission distance of the submarine fixed array system is relatively short, G.654.C fiber can be selected for transmission, which combines low transmission loss and high Raman amplification gain, while also being relatively cheaper. When the transmission distance of the submarine fixed array system is relatively long, G.654.D fiber can be selected for transmission, which combines low transmission loss and high optical power threshold.

[0051] For example, the transmission optical fiber can also be a combination of G.654.C fiber and G.654.D fiber, giving the submarine fixed array system both performance and cost advantages.

[0052] For example, when there are multiple fiber optic hydrophone arrays in the system, the system proposed in this invention can achieve remote transmission of multiple fiber optic hydrophone arrays by using a multi-fiber pair repeater.

[0053] For a 200km transmission fiber optic hydrophone array system, where the transmission fiber... and transmission fiber It is a 192km long G.654.D optical fiber, transmission fiber and transmission fiber Using an 8km long G.654.D optical fiber, the fiber optic hydrophone array adopts a 32 wavelength division × 8 time division multiplexing method. Based on the simulation of the remote transmission system proposed in this invention, the optical signal-to-noise ratio of each wavelength channel receiver (preamplifier output) can be obtained during the Beginning of Life (BOL) and End of Life (EOL) stages of the system. Figure 2 In the results shown, the optical signal-to-noise ratio (SNR) at the receiver of each wavelength channel during the BOL (Browser-to-Onset) stage is ≥20.8 dB. After aging and maintenance, the SNR at the receiver of each wavelength channel during the EOL (End-of-Life) stage is ≥19.0 dB, ensuring that the system phase noise is ≤ 10 dB throughout its entire lifespan. -90dB rad / √Hz@1kHz.

[0054] Example 2 Embodiment 2 of the present invention proposes a remote transmission method, which is implemented by a fiber optic hydrophone array remote transmission system as described in Embodiment 1.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A long-distance transmission system for fiber optic hydrophone arrays, used for long-distance broadband optical transmission of fiber optic hydrophone arrays more than 150km offshore, characterized in that, The system includes: an optical transmitting module, an optical receiving module, a Raman pumping unit, and a status management unit at the dry end, and a repeater amplifier and an optical fiber hydrophone array at the wet end; The optical transmitting module is used to amplify the power of the pre-emphasized downlink multi-wavelength laser pulses before transmitting them through the transmission optical fiber. Input repeater amplifier; The optical receiving module is used to receive light transmitted through the optical fiber. The input uplink multi-wavelength interference optical signal is pre-amplified and processed to restore the sound field information; The relay amplifier is used to transmit the signal via optical fiber. The input downlink multi-wavelength laser pulses are then remotely amplified by high-gain, low-noise optical amplification and transmitted via optical fiber. Input fiber optic hydrophone array; also used for the transmission of fiber optic cables. The input uplink multi-wavelength interference optical signal is remotely amplified by high gain and low noise before being transmitted through optical fiber. To the optical receiver module; The Raman pumping unit is connected to the transmission optical fiber. Optical coupling connection, outputting multi-wavelength Raman pump light, used in transmission optical fibers The uplink multi-wavelength interference optical signal output from the relay amplifier is subjected to reverse distributed fiber Raman amplification to improve gain flatness; The status management unit is connected to the optical emission module, optical receiving module, and Raman pumping unit. It is used to configure different wavelength Raman pumping laser powers for the Raman pumping unit and to monitor the operating status of the system. The fiber optic hydrophone array is used to receive signals transmitted via optical fiber. The input downlink multi-wavelength laser pulses are also used to output multi-wavelength interference light signals carrying acoustic field information to the transmission optical fiber. .

2. The fiber optic hydrophone array remote transmission system according to claim 1, characterized in that, The relay amplifier includes a downlink amplifier unit and an uplink amplifier unit.

3. The fiber optic hydrophone array remote transmission system according to claim 2, characterized in that, The optical emission module includes an optical emission unit and a power amplifier; wherein... The optical emitting unit is used to output multi-wavelength laser pulses with pre-emphasized power; The input terminal of the power amplifier is optically connected to the output terminal of the optical emitting unit, and the output terminal of the power amplifier is connected via a transmission optical fiber. Connected to the input of the downlink amplification unit in a repeater amplifier, it is used to amplify the power of pre-emphasized multi-wavelength laser pulses and inject them into the transmission fiber. .

4. The fiber optic hydrophone array remote transmission system according to claim 3, characterized in that, The optical receiving module includes: a preamplifier and an optical receiving unit, wherein... The output of the preamplifier is optically connected to the input of the optical receiving unit, and the input of the preamplifier is connected to the transmission optical fiber. It is connected to the output of the uplink amplifier unit in the repeater amplifier to improve the receiving sensitivity of the optical receiver unit; The optical receiving unit is used to perform wavelength division multiplexing, optical power adjustment, photoelectric conversion, analog-to-digital conversion and digital demodulation of multi-wavelength interference optical signals, and to restore the sound field information.

5. The fiber optic hydrophone array remote transmission system according to claim 1, characterized in that, The system also includes a remote power supply unit, via an electrical conductor. Connected to a relay amplifier and via a signal connection to a status management unit, the remote power supply unit is a high-voltage constant current source used to achieve remote power supply.

6. The fiber optic hydrophone array remote transmission system according to claim 5, characterized in that, The transmission optical fiber Fiber optic transmission Fiber optic transmission Fiber optic transmission and electrical conductors All are integrated into the submarine optical cable, including the transmission optical fiber. Fiber optic transmission Fiber optic transmission and transmission fiber To achieve optical transmission, G.654.C or G.654.D optical fiber is used; electrical conductors are also required. To achieve electrical transmission.

7. The fiber optic hydrophone array remote transmission system according to claim 1 or 6, characterized in that, The transmission optical fiber and transmission fiber The transmission optical fibers are of equal length. and transmission fiber The lengths of the optical fibers are equal; and the transmission optical fibers are... and transmission fiber The sum of the lengths of the transmission optical fiber and transmission fiber The sum of their lengths is equal.

8. The fiber optic hydrophone array remote transmission system according to claim 4, characterized in that, The power amplifier, preamplifier, and repeater amplifier are erbium-doped fiber amplifiers or ytterbium-erbium co-doped fiber amplifiers.

9. A remote transmission method, characterized in that, The method is implemented using the fiber optic hydrophone array remote transmission system as described in any one of claims 1-8.

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