CN212721728U - Orthogonal frequency division multiplexing-based high-frequency response optical fiber hydrophone array detection system - Google Patents
Orthogonal frequency division multiplexing-based high-frequency response optical fiber hydrophone array detection system Download PDFInfo
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- CN212721728U CN212721728U CN202021344444.4U CN202021344444U CN212721728U CN 212721728 U CN212721728 U CN 212721728U CN 202021344444 U CN202021344444 U CN 202021344444U CN 212721728 U CN212721728 U CN 212721728U
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Abstract
A high-frequency response optical fiber hydrophone array detection system based on orthogonal frequency division multiplexing comprises: light source ware, optical modulator, optic fibre hydrophone array, coherent receiver and signal detector, wherein: the light source device is respectively connected with the optical modulator and the coherent receiver, the optical modulator is connected with the optical fiber hydrophone array, the optical fiber hydrophone array is connected with the coherent receiver, and the coherent receiver is connected with the signal detector; the utility model discloses a sensing is realized to the detection light pulse of a plurality of mutual orthorhombic and the mode of coherent reception response, utilizes simple demodulation algorithm, realizes intensive frequency division multiplexing to improve the detection frequency to hydrophone array.
Description
Technical Field
The utility model relates to a technology in acoustic signal sensing field under water specifically is a high frequency response optic fibre hydrophone array detection system based on orthogonal frequency division multiplexing.
Background
In order to realize the positioning of underwater targets, massive multiplexing of hydrophones is required. With the increase of the multiplexing scale, the fiber optic hydrophone array system is limited by the traveling and returning time of the detection light in the optical fiber, and the problem of insufficient frequency response is presented. For an optical fiber hydrophone array system with the multiplexing scale reaching 50km, the current technology can only realize the frequency response of 1kHz and cannot meet the requirement of acoustic signal sensing.
SUMMERY OF THE UTILITY MODEL
The utility model discloses to the above-mentioned not enough that prior art exists, provide a high frequency response optic fibre hydrophone array detection system based on orthogonal frequency division multiplexing, the mode through the detection light pulse of a plurality of mutual orthogonalizations and coherent reception response realizes the sensing, improves the detection frequency to hydrophone array.
The utility model discloses a realize through following technical scheme:
the utility model relates to a high frequency response optic fibre hydrophone array detection system based on orthogonal frequency division multiplexing, include: light source ware, optical modulator, optic fibre hydrophone array, coherent receiver and signal detector, wherein: the light source device is respectively connected with the optical modulator and the coherent receiver, the optical modulator is connected with the optical fiber hydrophone array, the optical fiber hydrophone array is connected with the coherent receiver, the coherent receiver is connected with the signal detector, and the signal detector obtains the corresponding phase of the reflected light signal through matched filtering and demodulation and realizes high sampling rate detection of the acoustic signal.
The light source device comprises: a narrow linewidth laser and a first fiber coupler, wherein: the narrow linewidth laser is connected with a first optical fiber coupler, and the first optical fiber coupler is respectively connected with the optical modulator and the coherent receiver.
The optical modulator comprises: electric signal generator, radio frequency amplifier and acousto-optic modulator that link to each other in proper order, wherein: the electric signal generator sends the generated carrier electric signal to the radio frequency amplifier, and the radio frequency amplifier amplifies the power of the electric signal and drives the acousto-optic modulator.
The coherent receiver comprises: a second fiber coupler and a balanced photodetector, wherein: the second optical fiber coupler receives the signal light transmitted by the optical fiber circulator and the local light transmitted by the first optical fiber coupler to carry out interference, and the interference signal is converted into a current signal through the balanced photoelectric detector.
The optical fiber hydrophone array comprises: optical fiber circulator and hydrophone array that links to each other, wherein: the optical fiber circulator is respectively connected with the hydrophone array and the coherent receiver.
The signal detector comprises: a signal collector and a data processor.
Technical effects
The utility model discloses wholly having solved current optic fibre hydrophone array system when surveying extensive hydrophone array, because received the restriction of surveying the optical pulse in optic fibre on the contrary time, the system that leads to is to the lower problem of the detection frequency of optic fibre.
Compared with the prior art, the utility model discloses use coherent detection to be the detection system structure on the basis, be aided with modulation and demodulation on the basis of orthogonal frequency division multiplexing modulation, can show the detection frequency who promotes long distance optic fibre hydrophone array.
Drawings
FIG. 1 is a schematic view of the present invention;
FIG. 2 is a schematic diagram of a received signal according to the present embodiment;
FIG. 3 is a diagram illustrating the noise level of demodulated signals before and after multiplexing according to an embodiment;
in the figure: the optical fiber circulator comprises a narrow-line-width laser 1, a first optical fiber coupler 2 and a first port a, a second port b, a third port c, an electric signal generator 3, a radio frequency amplifier 4, an acoustic optical modulator 5, a light circulator 6 and a first port a, a second port b, a third port c, an optical fiber hydrophone array 7, a second optical fiber coupler 8 and a first port a, a second port b, a third port c, a fourth port d, a balanced photoelectric detector 9, a signal collector 10 and a data processor 11.
Detailed Description
As shown in fig. 1, the present embodiment relates to a high frequency response fiber optic hydrophone array detection system based on orthogonal frequency division multiplexing, which includes: narrow linewidth laser 1, first fiber coupler 2, optical modulator, light circulator 6, optic fibre hydrophone array 7, second fiber coupler 8 and signal demodulation mechanism, wherein: the narrow linewidth laser 1 is connected with a port a of a first optical fiber coupler 2, a port b of the first optical fiber coupler 2 is connected with an optical modulator, a port c of the first optical fiber coupler 2 is connected with a port b of a second optical fiber coupler 8, the optical modulator is connected with a port a of an optical fiber circulator 6, a port b of the optical fiber circulator 6 is connected with an optical fiber hydrophone array 7, a port c of the optical fiber circulator 6 is connected with a port a of the second optical fiber coupler 8, and a third port c and a fourth port d of the second optical fiber coupler 8 are connected with a signal demodulation mechanism.
The optical fiber hydrophone array 7 is specifically arranged in the following way: reflection points (or equivalent structures such as fiber gratings or coupler-mirror combinations) with a reflectivity of-40 dB are connected with single-mode fibers at 20m intervals to form a 50km long array.
The narrow linewidth laser 1 generates laser light with constant power, and the first optical fiber coupler is used for transmitting the laser light according to the following proportion of 50: a proportion of 50 is allocated to the b-ports of the acousto-optic modulator 5 and the second coupler 8.
The optical modulator comprises: the device comprises an electric signal generator 3, a radio frequency amplifier 4 and an acousto-optic modulator 5 which are connected in sequence, wherein: the electrical signal generator 3 generates orthogonal radio frequency pulses with frequencies of 181.25MHz, 187.5MHz, 193.75MHz and 200MHz, respectively, and a pulse width of 100ns, and these signals are amplified by the radio frequency amplifier 4 and used to drive the acousto-optic modulator 5, which modulates the continuous light into pulse probe light with orthogonal carrier, and the probe light is transmitted to the fiber optic hydrophone array 7 through the fiber optic circulator 6.
The signal demodulating mechanism comprises: when detecting light is transmitted in the optical fiber hydrophone array 7, a reflection signal is periodically generated, the reflection signal is transmitted to the second optical fiber coupler 8 through the optical fiber circulator 6 and interferes with local light, the interference signal is converted into a current signal by the photoelectric detector 9, and the signal collector 10 discretizes the acquired current signal and processes the current signal by the data processor 11.
The present embodiment works by: the signal acquisition device 10 acquires an electrical signal generated by interference between a primary hydrophone array reflection signal and local light, and the data processor 11 performs matched filtering on the electrical signal and performs orthogonal demodulation after matched filtering to realize high sampling rate detection on an acoustic signal.
The electric signal { U (n) generated by the interference with the local light; n1, N represents a discrete signal generated after the process passes through the signal collector 11, with N as a variable, and its continuous time domain representation is:
The matched filtering algorithm is I (t) ═ Sigma U (t) × rect (t-nt)w-itr)cos(ωit) and q (t) ═ Σ u (t) × rect (t-nt)w-itr)sin(ωit)。
The orthogonal demodulation algorithm is
(t)＝arctan[I(t)/Q(t)]。
Compared with the prior art, the method realizes dense frequency division multiplexing, can improve the detection frequency of the system for the hydrophone array by 16 times, and realizes higher frequency response; the frequency spectrum utilization rate is higher, and the multiplexing of more paths of carriers can be realized; compared with the existing method for improving the frequency response by compressed sensing, the method can realize high-precision linear demodulation of the signal without losing other performances of the system.
Through specific tests, the frequency spectrum utilization rate of the method is as follows:
wherein: n is the number of multiplexed carriers. The hydrophone signals are demodulated by the demodulation method, and the noise level of the demodulated signals before and after multiplexing has no obvious change, as shown in fig. 3. This data can demonstrate that the introduction of the ofdm method does not degrade other performance of the system (e.g., sensitivity, probe length, etc.).
Compared with the prior art, the method can improve the detection frequency of the system for the hydrophone array to 16 times that of a common hydrophone detection system at the maximum under the limit that the maximum modulation bandwidth of the existing acoustic-optical modulator is 100 MHz.
The foregoing embodiments may be modified in various ways by those skilled in the art without departing from the spirit and scope of the present invention, which is not limited by the above embodiments but is to be accorded the full scope defined by the appended claims, and all such modifications and variations are within the scope of the invention.
Claims (7)
1. A high frequency response fiber optic hydrophone array detection system based on orthogonal frequency division multiplexing, comprising: light source ware, optical modulator, optic fibre hydrophone array, coherent receiver and signal detector, wherein: the light source device is respectively connected with the optical modulator and the coherent receiver, the optical modulator is connected with the optical fiber hydrophone array, the optical fiber hydrophone array is connected with the coherent receiver, and the coherent receiver is connected with the signal detector.
2. The ofdm-based high frequency response fiber optic hydrophone array detection system of claim 1, wherein the fiber optic hydrophone array is arranged in the following manner: reflection points having a reflectivity of-40 dB were connected by single-mode fibers at intervals of 20m to form a 50km long array.
3. The ofdm-based high frequency-response fiber optic hydrophone array detection system of claim 1, wherein said coherent receiver comprises: a second fiber coupler and a balanced photodetector.
4. The ofdm-based high frequency-response fiber optic hydrophone array probe system of claim 1, wherein said optical source comprises: a narrow linewidth laser and a first fiber coupler, wherein: the narrow linewidth laser is connected with a first optical fiber coupler, and the first optical fiber coupler is respectively connected with the optical modulator and the coherent receiver.
5. The ofdm-based high frequency-response fiber optic hydrophone array detection system of claim 1, wherein said optical modulator comprises: an electric signal generator, a radio frequency amplifier and an acousto-optic modulator which are connected in sequence.
6. The ofdm-based high frequency response fiber optic hydrophone array detection system of claim 1, wherein said fiber optic hydrophone array comprises: optical fiber circulator and hydrophone array that links to each other, wherein: the optical fiber circulator is respectively connected with the hydrophone array and the coherent receiver.
7. The ofdm-based high frequency-responsive fiber optic hydrophone array detection system of claim 1, wherein said signal detector comprises: a signal collector and a data processor.
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| CN111780853A (en) * | 2020-07-10 | 2020-10-16 | 上海交通大学 | Optical fiber hydrophone array high-frequency response detection method based on orthogonal frequency division multiplexing |
| CN111780853B (en) * | 2020-07-10 | 2024-07-16 | 上海交通大学 | Optical fiber hydrophone array high-frequency response detection method based on orthogonal frequency division multiplexing |
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