CN111928936A - Light emitting device for optical fiber hydrophone array - Google Patents
Light emitting device for optical fiber hydrophone array Download PDFInfo
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Abstract
The invention provides a light emitting device for an optical fiber hydrophone array, which comprises N narrow-linewidth light sources, a wavelength division multiplexer, an acousto-optic modulator assembly, a first optical fiber amplifier, a wavelength division delay and pre-emphasis assembly and a second optical fiber amplifier, wherein N is a natural number larger than 1, and the number of the N is equal to that of wavelength division multiplexing channels of the optical fiber hydrophone array. The light emitting device outputs multi-wavelength light pulses by wavelength division delay and pre-emphasis components in a wavelength division delay peak-shifting manner, performs power pre-emphasis, and then performs power amplification, thereby fully realizing multi-wavelength high-power light amplification, greatly reducing spontaneous radiation noise, nonlinear noise accumulation and waveform distortion while improving the output power, improving the output light pulse power and signal-to-noise ratio of the light emitting device, effectively improving the long-distance transmission performance, and improving the transmission distance of a shore-based fixed optical fiber hydrophone array and the detection capability of weak signals.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a light emitting device for an optical fiber hydrophone array.
Background
Acoustic waves are the only form of energy radiation that can propagate remotely under water. The hydrophone is a sensor for detecting, positioning and identifying underwater targets by using sound waves, and is an underwater radar in modern military. The optical fiber hydrophone is used as a novel underwater sound detection device, shows incomparable advantages of the traditional piezoelectric hydrophone from the birth date, such as high sensitivity, wider bandwidth, full wet-end light, high stability, high temperature resistance, corrosion resistance, long transmission distance, large-scale reuse and the like, and is gradually substituted for the traditional piezoelectric hydrophone to be applied in multiple fields of military affairs, commerce, scientific research and the like.
The seabed shore-based fixed optical fiber sonar system is one of the main application forms of an optical fiber hydrophone array, and is the most advanced ocean passive detection system at present. In recent years, with the continuous improvement of the ship target noise reduction technology and the continuous improvement of the requirements on the detection distance and the detection precision of a sonar system, the scale of a seabed shore-based fixed fiber array is continuously enlarged, the number of elements is increased to thousands or even tens of thousands, and the transmission distance is gradually extended to hundreds or even thousands of kilometers.
The relay transmission and the unrepeatered transmission are two application forms of the long-distance transmission of a seabed shore-based fixed optical fiber sonar system, wherein the unrepeatered transmission supports the transmission requirement of an optical fiber hydrophone array at the hundred kilometers level, and the relay transmission supports the transmission requirement of the optical fiber hydrophone array at the thousand kilometers level, thereby providing support for offshore and open sea detection. The optical fiber hydrophone array usually adopts a group array mode of time division, wavelength division and space division hybrid multiplexing, but as a bank-based fixed optical fiber array develops towards the direction of super-large scale and super-long distance, the array mostly adopts the time division and wavelength division hybrid multiplexing mode, and by multiplexing 128-element or even 256-element optical fiber hydrophone arrays through single fiber pairs, the number of optical fiber pairs is greatly reduced, and the complexity and the cost of a system are reduced. However, the large-scale dense multiplexing long-distance transmission system puts higher requirements on the optical transmitting device, and mainly has the following points: (1) multi-wavelength, high power, low repetition frequency, low duty cycle optical pulse or pulse pair output: for an NxM hybrid multiplexing system (N is the number of wavelength division multiplexing, M is the number of time division multiplexing), the light emitting device is required to output multiplexing optical pulses or pulse pairs with N wavelength and low duty ratio (less than or equal to 1/M) with the total power of more than 16dBm, the pulse width is in the magnitude of hundreds of ns, and the pulse repetition frequency is in the magnitude of hundreds of kHz; (2) in order to improve the detection capability of a long-distance transmission shore-based fixed optical fiber array on weak signals, a light emitting device is required to output multi-wavelength optical pulses or pulse pair signals with high optical signal to noise ratio (OSNR), and the light emitting device has the function of inhibiting linear and nonlinear noises in the processes of light amplification and transmission; (3) in order to improve the consistency of the performance of each wavelength channel of a remote transmission shore-based fixed fiber sonar system and avoid the performance degradation of the system caused by the unbalanced power caused by the remote transmission and amplification of multi-wavelength optical signals, a light emitting device is required to have the function of pre-emphasis of the wavelength channel power.
At present, a light emitting device commonly used in an optical fiber hydrophone array system adopts a mode of simultaneously amplifying and outputting multi-wavelength light pulses with high gain and high power, taking an N × M wavelength division/time division hybrid multiplexing system as an example, the existing light emitting device is structured by N optical fiber hydrophones with equal wavelength intervals and using a narrow line width light source (λ)1～λN) The light is multiplexed to a single optical fiber by a wavelength division multiplexer, the output of the wavelength division multiplexer is connected with an acousto-optic modulator module to generate multiplexed light pulse or pulse pair with specific duty ratio (less than or equal to 1/M), the multiplexed light pulse or pulse pair simultaneously enters a multi-wavelength optical fiber power amplifier, the multiplexed light pulse or pulse pair is output after being amplified by high gain and high power, and the N wavelength multiplexed light pulse or pulse pair after being amplified by the power is simultaneously input to a long-distance transmission system for transmission. Remote transmission shore-based fixed type based on light emitting deviceThe optical fiber sonar system still has technical defects:
first, the multi-wavelength optical fiber power amplifier may generate a severe four-wave mixing (FWM) effect during the simultaneous high-gain power amplification of N-wavelength multiplexed optical pulses or pulse pairs, causing frequency shift and consumption of wavelength channels, reducing the optical power and optical signal-to-noise ratio of the output signal of the optical transmitting device, and further deteriorating the performance of the wavelength channels in long-distance transmission. The erbium-doped gain fiber in the multi-wavelength fiber power amplifier has the advantages of small effective area compared with the fiber core of a common single-mode fiber, high peak power of a multiplexing optical pulse or pulse pair with low duty ratio, large power density, short acting distance (usually tens of m magnitude), and good phase matching condition of each wavelength channel. In addition, light pulse or pulse pair with low duty ratio enters the optical fiber power amplifier to be amplified with high gain power at the same time, the optical fiber power amplifier generates violent population inversion in a time period of less than or equal to 1/M, excited particles are rapidly consumed, gain saturation is generated, and the phenomenon of high front and low back distortion of the light pulse occurs; in the time period greater than (M-1)/M, a large number of excited particles are in an idle state for a long time, serious spontaneous radiation is generated, a large number of spontaneous radiation (ASE) noises are introduced, the increase of the ASE noises deteriorates the output optical signal-to-noise ratio of the light emitting device, further the phase noise of the shore-based fixed optical fiber sonar system is deteriorated, and the detection capability of weak signals is reduced.
Secondly, in the long-distance unrepeatered transmission system, in order to compensate for the huge loss caused by long-distance transmission and large-scale dense multiplexing optical fiber hydrophone arrays, a common optical transmitting device outputs high-power multi-wavelength optical pulse signals to enter the long-distance unrepeatered transmission system, and the high-power multi-wavelength optical pulse signals generate serious spontaneous raman scattering effect in the long-distance optical fiber transmission process, so that long-wavelength signals are amplified by short-wavelength signals to cause energy red shift, wherein the shortest and longest wavelength channels have the most serious influence, and because the shortest and longest wavelength channels transfer energy to other wavelength channels in the gain bandwidth, the power imbalance of the wavelength channels is aggravated, and the optical signal-to-noise ratio of the short-wavelength channels is seriously reduced. In addition, in order to further increase the unrepeatered transmission distance, a fiber raman amplifier is usually introduced to compensate for the fiber transmission loss, the fiber raman amplifier utilizes the stimulated raman scattering effect to perform pump amplification on the signal light, and the unevenness of the raman gain spectrum further aggravates the imbalance of the power of each wavelength channel, which seriously affects the consistency of the performance of each wavelength channel. Due to the uneven amplification characteristic of the Raman scattering effect, the power level of some wavelength channels is too high in the transmission process, the nonlinear effect is obvious, the nonlinear noise accumulation is serious, the power level of other wavelength channels is too low in the transmission process, the optical signal-to-noise ratio is seriously reduced, the overall performance of the system is deteriorated, and the long-distance unrepeatered transmission distance is limited.
In addition, in a long-distance relay transmission system, uneven gain spectrum of a relay amplifier causes power imbalance of each wavelength channel to be aggravated along with increase of the cascade stage number of the relay, and also causes some wavelength channels to maintain an excessively high power level in the transmission process, so that the nonlinear effect is obvious, nonlinear noise accumulation is serious, and the other wavelength channels have excessively low power levels in the transmission process, so that the optical signal to noise ratio is seriously reduced, and the overall performance of the system is deteriorated. In addition, the mismatch between the gain of the relay amplifier and the loss of the corresponding span fiber also causes the gain spectrum of the relay amplifier to tilt within the signal bandwidth, which aggravates the imbalance of the power of each wavelength channel. In addition, the multi-wavelength optical pulse simultaneously enters the relay transmission system, and at the moment when the optical pulse is turned on and off, an optical surge phenomenon can be generated, so that the generation of the optical surge phenomenon can cause the instantaneous increase of output power, a serious nonlinear effect can be generated, the accumulation of nonlinear noise is serious, and the system performance is deteriorated.
In summary, although the existing optical fiber hydrophone optical transmission device scheme can realize the output of multi-wavelength and low-duty-ratio optical pulses or pulse pairs, the existing optical fiber hydrophone optical transmission device scheme cannot meet the requirements of high power, high optical signal-to-noise ratio, linear and nonlinear noise suppression in the optical amplification and transmission processes and pre-emphasis on the wavelength channel power. Therefore, aiming at the application requirement of large-scale dense multiplexing remote transmission, the bottleneck of the prior technical scheme is urgently needed to be broken through, a high-performance light emitting device which can simultaneously meet the requirements of multiple wavelengths, high power, low duty ratio, high optical signal-to-noise ratio and low noise and has a wavelength channel power pre-emphasis function is developed, and the high-performance light emitting device is applied to the relevant fields of a shore-based fixed optical fiber sonar system of large-scale dense multiplexing remote transmission and the like.
Disclosure of Invention
The present invention is directed to solving the problems described above. It is an object of the present invention to provide a light emitting device that solves any of the above problems. Specifically, the invention provides an optical transmission device which can simultaneously meet the requirements of multiple wavelengths, high power, low duty ratio, high optical signal-to-noise ratio and low noise and has a wavelength channel power pre-emphasis function.
In order to solve the technical problem, the invention provides a light emitting device for an optical fiber hydrophone array, which comprises N narrow linewidth light sources, a wavelength division multiplexer, an acoustic optical modulator assembly, a first optical fiber amplifier, a wavelength division delay and pre-emphasis assembly and a second optical fiber amplifier, wherein N is a natural number greater than 1, and the number of wavelength division multiplexing channels of the optical fiber hydrophone array is equal to that of N;
the wavelength division multiplexer comprises N input ports which are respectively connected with the output ends of the N narrow line width light sources in a one-to-one correspondence manner and is used for combining N beams of optical signals with different wavelengths, which are sent by the N narrow line width light sources, into a beam of multi-wavelength continuous optical signal and outputting the multi-wavelength continuous optical signal;
the acousto-optic modulator assembly is connected with an output port of the wavelength division multiplexer through an optical fiber and is used for modulating the multi-wavelength continuous optical signal into a multi-wavelength optical pulse signal and outputting the multi-wavelength optical pulse signal;
the first optical fiber amplifier is connected with an output port of the acousto-optic modulator assembly through an optical fiber and is used for pre-amplifying and outputting multi-wavelength optical pulse signals;
the wavelength division delay and pre-emphasis component is connected with an output port of the first optical fiber amplifier through an optical fiber and is used for performing wavelength division delay and power pre-emphasis processing on a multi-wavelength optical pulse signal and outputting the multi-wavelength optical pulse signal;
and the second optical fiber amplifier is connected with the output port of the wavelength division delay and pre-emphasis component through an optical fiber and is used for carrying out high-gain power amplification on the output signal of the wavelength division delay and pre-emphasis component and outputting the amplified signal.
The wavelength division delay and pre-emphasis component comprises a multi-wavelength optical pulse input port, a wavelength division delay branch, a power pre-emphasis branch, a wave combination branch and an output port, wherein the multi-wavelength optical pulse input port is connected with the output end of the first optical fiber amplifier through an optical fiber, and the wavelength division delay branch is used for sequentially delaying and downloading optical pulses with various wavelengths in a multi-wavelength optical pulse signal; the power pre-emphasis branch is used for independently adjusting the power of the optical pulse with each wavelength downloaded by the wave division delay branch; the wave combining branch is used for sequentially uploading and combining the optical pulses with the wavelengths regulated by the power pre-emphasis branch to synthesize a multi-wavelength quasi-continuous optical signal with pre-emphasized power; and the output port is used for outputting the combined multi-wavelength quasi-continuous optical signal.
The wave-splitting delay branch circuit comprises N wave-splitting devices and N-1 optical fiber delay rings which are alternately arranged with the N wave-splitting devices, the power pre-emphasis branch circuit comprises N electric variable optical attenuators, and the wave-combining branch circuit comprises N wave-combining devices, wherein the N wave-splitting devices are connected with the N electric variable optical attenuators in a one-to-one correspondence manner, and the N electric variable optical attenuators are connected with the N wave-combining devices in a one-to-one correspondence manner.
The optical attenuator comprises an electric adjustable optical attenuator, a wave-combining device and a light-transmitting device, wherein the wave-splitting device comprises a broadband input port, a narrowband optical download port and a broadband output port, the electric adjustable optical attenuator comprises an attenuation input port and an attenuation output port, and the wave-combining device comprises a wave-combining input port, a narrowband optical upload port and a wave-combining output port; the optical fiber coupling device comprises an ith optical splitter, an ith electric variable optical attenuator, an ith narrow-band optical down-load port, an ith narrow-band optical up-load port and an ith narrow-band optical down-load port, wherein the narrow-band optical down-load port of the ith optical splitter is connected with the attenuation input port of the ith electric variable optical attenuator through an optical fiber; the broadband output port of the ith wave splitter is connected with the broadband input port of the (i + 1) th wave splitter through the ith optical fiber delay ring, and the wave combining output port of the ith wave combining device is connected with the wave combining input port of the (i + 1) th wave combining device through an optical fiber; i is a positive integer greater than or equal to 1 and less than N.
The broadband input port of the 1 st wave splitter is connected with the multi-wavelength optical pulse input port through an optical fiber, and the wave combining output port of the Nth wave combiner is connected with the output port through an optical fiber.
And adjacent wave-splitting devices of the wave-splitting delay branch circuit are connected through the optical fiber delay ring.
The lengths D of the delay optical fibers between two adjacent wave-splitting devices in the wave-splitting delay branch are the same:
wherein c is the speed of light in vacuum, T is the period of light pulse, N is the refractive index of the delay optical fiber, M is the number of time division multiplexing channels of the optical fiber hydrophone array, and min (M, N) is the minimum value of M and N.
Wherein the acousto-optic modulator assembly is driven by a TTL level.
The duty ratio of a multi-wavelength optical pulse signal output by the acousto-optic modulator component is less than or equal to 1/M, wherein M is the number of time division multiplexing channels of the optical fiber hydrophone array.
The first optical fiber amplifier is an erbium-doped optical fiber amplifier, and the second optical fiber amplifier is an erbium-doped optical fiber amplifier.
The light emitting device outputs multi-wavelength composite light pulse by wavelength division delay and pre-emphasis components, performs power pre-emphasis and then performs power amplification, fully realizes multi-wavelength high-power light amplification, greatly reduces spontaneous radiation noise, nonlinear noise accumulation and waveform distortion while improving output power, improves output light pulse power and signal-to-noise ratio of the light emitting device, effectively improves remote transmission performance, and improves transmission distance of a shore-based fixed optical fiber hydrophone array and detection capability of weak signals.
Other characteristic features and advantages of the invention will become apparent from the following description of exemplary embodiments, which is to be read in connection with the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings, like reference numerals are used to indicate like elements. The drawings in the following description are directed to some, but not all embodiments of the invention. For a person skilled in the art, other figures can be derived from these figures without inventive effort.
Fig. 1 schematically shows a schematic view of a light emitting device of the present invention;
FIG. 2 schematically illustrates a wavelength division delay and pre-emphasis component;
FIG. 3 schematically illustrates a pulse timing diagram for a wavelength division delay and pre-emphasis module multi-wavelength pulse input port;
FIG. 4 is a schematic diagram illustrating the power and timing of multi-wavelength optical pulses at the output port of the M ≧ N wavelength division delay and pre-emphasis module;
fig. 5 is a schematic diagram illustrating the power and timing of the multi-wavelength optical pulse at the output port of the M < N time wavelength division delay and pre-emphasis module.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
The invention delays the low-duty-ratio light pulses output by multiple wavelengths simultaneously to the whole pulse period in a wavelength-division sequence through the wavelength-division delay and pre-emphasis component, adjusts the power of each wavelength light pulse according to the requirement and outputs multi-wavelength continuous light subjected to power pre-emphasis. In a non-relay transmission system, the sub-wavelength delay equivalently introduces dispersion, thereby greatly reducing the multi-wavelength power imbalance caused by spontaneous Raman scattering effect; the power pre-emphasis can effectively compensate the multi-wavelength power imbalance caused by uneven gain of the optical fiber Raman amplifier in the signal bandwidth, reduce the accumulation of nonlinear noise and increase the unrepeatered transmission distance. In a relay transmission system, multi-wavelength continuous light is output in a wavelength-division delay manner, so that the optical surge phenomenon caused by power fluctuation in the process of simultaneously switching on and off multi-wavelength optical pulses can be effectively avoided, and the stability of the system is enhanced; the power pre-emphasis can effectively compensate gain unevenness of the cascade repeater and gain spectrum inclination caused by mismatching of the repeater gain and corresponding span loss, reduce power imbalance of each wavelength channel, reduce nonlinear noise accumulation and improve the detection capability of the optical fiber hydrophone array on weak signals. The scheme realizes the functions of wavelength division delay peak staggering output and power pre-emphasis of the multi-wavelength optical pulse in the same component, has high integration level, can greatly improve the performance of the multi-wavelength high-power light emitting device, can effectively improve the long-distance transmission performance, and has important significance for improving the transmission distance of the shore-based fixed optical fiber hydrophone array and the detection capability of weak signals.
The following describes in detail a light emitting device for a fiber optic hydrophone array according to the present invention with reference to the accompanying drawings.
Fig. 1 is a schematic diagram showing an embodiment of the light emitting device for a fiber optic hydrophone array according to the present invention, and referring to fig. 1, the light emitting device includes N narrow linewidth light sources 1 for emitting N continuous light signals with different wavelengths, and further includes a wavelength division multiplexer 2, an acousto-optic modulator module 3, a first fiber amplifier 4, a wavelength division delay and pre-emphasis module 5, and a second fiber amplifier 6, where N is a natural number greater than 1, and is equal to the number of wavelength division multiplexing channels of the fiber optic hydrophone array.
In particular, the amount of the solvent to be used,the wavelength division multiplexer 2 comprises N input ports and 1 output port, wherein the N input ports of the wavelength division multiplexer 2 are respectively connected with the output ends of the N narrow line width light sources 1 in a one-to-one correspondence manner and are used for combining N beams of optical signals with different wavelengths, which are emitted by the N narrow line width light sources 1, into a beam of multi-wavelength continuous optical signal and outputting the beam; the input port of the acoustic optical modulator component 3 is connected with the output port of the wavelength division multiplexer 2 through an optical fiber, and is used for modulating the multi-wavelength continuous optical signal synthesized by the wavelength division multiplexer 2 into a multi-wavelength composite optical pulse signal and outputting the multi-wavelength composite optical pulse signal; the acousto-optic modulator component 3 is driven by TTL level, the pulse characteristic of the TTL level, the time division multiplexing number M of the optical fiber hydrophone array and the repetition frequency fcAnd the demodulation method, which will not be described herein. The input port of the first optical fiber amplifier 4 is connected with the output port of the acousto-optic modulator component 3 through an optical fiber, and is used for pre-amplifying and outputting the multi-wavelength composite optical pulse signal modulated by the acousto-optic modulator component 3; the wavelength division delay and pre-emphasis component 5 is connected with an output port of the first optical fiber amplifier 4 through an optical fiber, and is used for performing wavelength division delay and power pre-emphasis processing on the multi-wavelength composite light pulse signal and outputting the multi-wavelength composite light pulse signal; the second optical fiber amplifier 6 is connected with the output port of the wavelength division delay and pre-emphasis module 5 through an optical fiber, and is used for performing high-gain power amplification on the output signal of the wavelength division delay and pre-emphasis module 5 to form a high-power wavelength division delay multi-wavelength optical pulse and output the high-power wavelength division delay multi-wavelength optical pulse.
According to the technical scheme, the wavelength division delay and pre-emphasis component 5 is adopted to perform wavelength division delay and power pre-emphasis adjustment on the multi-wavelength composite light pulse and then output peak staggering, so that the power imbalance of each wavelength channel in long-distance transmission is reduced, the nonlinear noise accumulation is reduced, and the detection capability of the optical fiber hydrophone array on weak signals is improved.
Fig. 2 is a schematic diagram illustrating an embodiment of the wavelength division delay and pre-emphasis module 5, and referring to fig. 1 and fig. 2, the wavelength division delay and pre-emphasis module 5 includes a multi-wavelength optical pulse input port 51, a wavelength division delay branch 52, a power pre-emphasis branch 53, a wavelength combining branch 54, and an output port 55. The multi-wavelength optical pulse input port 51 is connected with the output end of the first optical fiber amplifier 4 through an optical fiber, and is used for inputting the multi-wavelength composite optical pulse signal pre-amplified by the first optical fiber amplifier 4 into the wavelength division delay and pre-emphasis component 5; the wavelength division delay branch 52 is used for sequentially delaying and downloading the optical pulses of each wavelength in the multi-wavelength composite optical pulse signal; the power pre-emphasis branch 53 is used for independently adjusting the optical pulse power of each wavelength downloaded by the wave-splitting delay branch 52; the wave combining branch 54 is used for sequentially uploading and combining the optical pulses with the wavelengths adjusted by the power pre-emphasis branch 53 to combine the multi-wavelength quasi-continuous optical signals with pre-emphasized power; the output port 55 is used for outputting the combined multi-wavelength quasi-continuous optical signal.
The wave-division delay branch 52 includes N wave-division devices 521 (ODM)1～ODMN) And N-1 fiber delay rings 522 (D) alternately arranged with the N wavelength division devices 5211～DN-1) The power pre-emphasis branch 53 comprises N electrically variable optical attenuators 531 (VOA)1～VOAN) The multiplexing branch 54 includes N multiplexing devices 541 (OAM)1～OAMN) (ii) a The N wave splitting devices 521 are connected to the N electrically adjustable optical attenuators 531 in a one-to-one correspondence, and the N electrically adjustable optical attenuators 531 are connected to the N wave combining devices 541 in a one-to-one correspondence.
In the present invention, the wave-splitting delay branch 52, the power pre-emphasis branch 53 and the wave-combining branch 54 are arranged in a symmetrical series structure. Specifically, each of the wavelength division devices 521 includes a broadband input port, a narrowband optical download port, and a broadband output port; each of the electrical variable optical attenuators 531 includes an attenuation input port and an attenuation output port, and each of the wave combining devices 541 includes a wave combining input port, a narrowband optical upload port, and a wave combining output port. The wave separating device 521, the electrically adjustable optical attenuator 531 and the wave combining device 541 are arranged in a one-to-one correspondence manner: the narrow-band optical down load port of the ith wave-splitting device 521 is connected with the attenuation input port of the ith electrically adjustable optical attenuator 531 through an optical fiber, and the attenuation output port of the ith electrically adjustable optical attenuator 531 is connected with the narrow-band optical up load port of the ith wave-combining device 541 through an optical fiber. Meanwhile, the N wave splitters 521 are arranged in series, that is, the broadband output port of the ith wave splitter 521 is connected with the broadband input port of the (i + 1) th wave splitter 521 through the ith optical fiber delay ring 522; the N wave-combining devices 541 are arranged in series, that is, the wave-combining output port of the i-th wave-combining device 541 is connected with the wave-combining input port of the (i + 1) -th wave-combining device 541 through an optical fiber; wherein i is a positive integer greater than or equal to 1 and less than N.
The broadband input port of the 1 st wave splitter 521 is connected to the multi-wavelength optical pulse input port 51 through an optical fiber, and the wave combining output port of the nth wave combiner 541 is connected to the output port 55 through an optical fiber.
In the present invention, the wave-division delay and pre-emphasis module 5 further includes a multi-wavelength power control port 56, and the N electrically variable optical attenuators 531 are independently controlled through the multi-wavelength power control port 56.
The adjacent wave-splitting devices 521 of the wave-splitting delay branch 52 are connected by an optical fiber delay ring 522. Furthermore, the connection optical fiber, the optical fiber delay ring 522 and the ports of the devices are welded by an optical fiber welding machine, and the welding points are protected by an optical fiber heat-shrinkable tube.
Specifically, the lengths D of the delay fibers between any two adjacent wave splitters 521 of the wave-splitting delay branch 52 are the same as:
in the formula, c is the speed of light in vacuum, T is the period of light pulse, N is the refractive index of the delay optical fiber, M is the time division multiplexing channel number of the optical fiber hydrophone array, N is the wavelength division multiplexing number of the optical fiber hydrophone array, and min (M, N) is the minimum value of M and N.
FIG. 3 is a schematic diagram of pulse timing for the input ports of multiple wavelength pulses of the WDM component 5 in which the multi-wavelength composite light pulse period T is defined by the system repetition frequency fcDetermining:
due to the widening effect of the acousto-optic modulator component on the TTL pulse, the time division is avoidedChannel pulse crosstalk, width τ of multi-wavelength composite light pulse in FIG. 31Should be less than the time division channel interval tau0：
τ0＝T/M
In practical application systems, the following two situations exist in the relationship between the number of wavelength division multiplexing N and the number of time division multiplexing M: m is more than or equal to N or less than N.
FIG. 4 is a schematic diagram showing the power and timing sequence of the multi-wavelength optical pulse at the output port of the wavelength division delay and pre-emphasis module 5 when M is greater than or equal to N, that is, when the wavelength division multiplexing number M is greater than or equal to the wavelength division multiplexing number N, the optical pulses with N wavelengths can be sequentially delayed and output at equal intervals within the period T, and the delay time τ between adjacent wavelengths2Satisfies the following conditions:
τ2＝T/N,τ2≥τ0>τ1
from the above delay time τ2Deterministic delay fiber (D)1～DN-1) The length D is:
D＝cT/nN
in the formula, c is the speed of light in vacuum, T is the period of light pulse, N is the refractive index of the delay optical fiber, and N is the wavelength division multiplexing number of the optical fiber hydrophone array.
Optical pulse power P of N wavelengths1～PNIndependent adjustment is performed according to the situation of the actual application system to achieve the purpose of balancing the power of each wavelength channel, which is not described herein.
FIG. 5 is a schematic diagram showing the power and timing sequence of the multi-wavelength optical pulse at the output port of the pre-emphasis module 5 when M < N, i.e. when the WDM M is smaller than the WDM N, the optical pulses with N wavelengths are delayed and output at equal intervals in turn in k periods T, and the delay time τ between k and the adjacent wavelength2Satisfies the following conditions:
τ2＝T/M,τ2>τ1
k is an integer not less than N/M, and when M is less than N, pulses in different periods T can be storedIn partial overlap, if the wavelengths of two overlapping pulses are each lambdaaAnd λb(b > a), then a and b satisfy:
b-a＝i×M,i＝1,2,…k-1
by the above-mentioned delay time tau2Deterministic delay fiber (D)1～DN-1) The length D is:
D＝cT/nM
in the formula, c is the speed of light in vacuum, T is the period of light pulse, n is the refractive index of the delay optical fiber, and M is the time division multiplexing number of the optical fiber hydrophone array.
Optical pulse power P of N wavelengths1～PNIndependent adjustment is performed according to the situation of the actual application system to achieve the purpose of balancing the power of each wavelength channel, which is not described herein.
In summary, under the conditions that M is greater than or equal to N and M is less than N, the peak-shifted output of the multi-wavelength composite optical pulse can be realized as multi-wavelength quasi-continuous light through the parameter design, and the power of the N wavelength optical pulses can be independently adjusted according to the actual application requirements.
The wavelength division delay and pre-emphasis module 5 sequentially delays the low-duty ratio optical pulse signals of multiple wavelengths, which are pre-amplified by the first optical fiber amplifier 4 and are simultaneously output, into the whole pulse period in a wavelength division mode through the combination of the wavelength division delay branch 52, the power pre-emphasis branch 53 and the wave combination branch 54, adjusts the power of the optical pulse of each wavelength according to the requirement, and finally outputs the multi-wavelength quasi-continuous optical signal subjected to power pre-emphasis. The wavelength division delay and pre-emphasis component 5 is applied to a light emitting device of an optical fiber hydrophone array remote transmission system, when multi-wavelength quasi-continuous optical signals subjected to wavelength division delay are subjected to power amplification through a second optical fiber amplifier 6, excited state particles in the whole pulse period can be fully utilized to realize multi-wavelength high-gain optical amplification, the output power is improved, meanwhile, the spontaneous radiation noise, nonlinear four-wave mixing noise and pulse distortion caused by gain saturation of the second optical fiber amplifier 6 are greatly reduced, and the output light pulse power and the signal-to-noise ratio of the light emitting device are improved.
In a non-relay transmission system, the wave-splitting delay is equivalent to introducing dispersion, so that the multi-wavelength power imbalance caused by the spontaneous Raman radiation effect is greatly reduced; the power pre-emphasis can effectively compensate the multi-wavelength power imbalance caused by uneven gain of the optical fiber Raman amplifier in the signal bandwidth, reduce the accumulation of nonlinear noise and increase the unrepeatered transmission distance.
In a relay transmission system, the sub-wavelength delay outputs multi-wavelength quasi-continuous optical signals, so that the optical surge phenomenon caused by power fluctuation in the process of simultaneously switching on and off multi-wavelength optical pulses can be effectively avoided, and the stability of the system is enhanced; the power pre-emphasis can effectively compensate gain unevenness of the cascade relay and gain spectrum inclination caused by mismatching of the relay gain and the corresponding span, reduce power imbalance of each wavelength, reduce nonlinear noise accumulation and improve the detection capability of the optical fiber hydrophone array on weak signals.
The invention skillfully realizes the wavelength division delay peak-shifting output function and the power pre-emphasis function of the multi-wavelength optical pulse in one component, has high integration level, not only can greatly improve the performance of a multi-wavelength high-power light emitting device, but also can effectively improve the long-distance transmission performance, and has important significance for improving the transmission distance of a shore-based fixed optical fiber hydrophone array and the detection capability of weak signals.
In a particular embodiment, the acousto-optic modulator assembly 3 is driven by TTL levels.
Specifically, the duty ratio of the multi-wavelength optical pulse signal output by the acousto-optic modulator component 3 is less than or equal to 1/M, wherein M is the number of time division multiplexing channels of the optical fiber hydrophone array.
In the present invention, the first optical fiber amplifier 4 is an erbium-doped optical fiber amplifier supporting multi-wavelength amplification, and the second optical fiber amplifier 6 is an erbium-doped optical fiber amplifier supporting multi-wavelength amplification.
The above-described aspects may be implemented individually or in various combinations, and such variations are within the scope of the present invention.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: the above examples are only for illustrating the technical solutions of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The light emitting device for the optical fiber hydrophone array is characterized by comprising N narrow-linewidth light sources (1), a wavelength division multiplexer (2), an acousto-optic modulator assembly (3), a first optical fiber amplifier (4), a wavelength division delay and pre-emphasis assembly (5) and a second optical fiber amplifier (6), wherein N is a natural number larger than 1, and the number of the N is equal to that of wavelength division multiplexing channels of the optical fiber hydrophone array;
the wavelength division multiplexer (2) comprises N input ports which are respectively connected with the output ends of the N narrow line width light sources (1) in a one-to-one correspondence manner and are used for combining N beams of optical signals with different wavelengths, which are emitted by the N narrow line width light sources (1), into a beam of multi-wavelength continuous optical signal and outputting the beam of multi-wavelength continuous optical signal;
the acousto-optic modulator assembly (3) is connected with an output port of the wavelength division multiplexer (2) through an optical fiber and is used for modulating the multi-wavelength continuous optical signal into a multi-wavelength composite optical pulse signal and outputting the multi-wavelength composite optical pulse signal;
the first optical fiber amplifier (4) is connected with an output port of the acousto-optic modulator assembly (3) through an optical fiber and is used for pre-amplifying and outputting a multi-wavelength composite optical pulse signal;
the wavelength division delay and pre-emphasis component (5) is connected with an output port of the first optical fiber amplifier (4) through an optical fiber and is used for performing wavelength division delay and power pre-emphasis processing on the multi-wavelength composite optical pulse signal and outputting the multi-wavelength composite optical pulse signal;
and the second optical fiber amplifier (6) is connected with an output port of the wavelength division delay and pre-emphasis component (5) through an optical fiber and is used for amplifying and outputting an output signal of the wavelength division delay and pre-emphasis component (5) by high-gain power.
2. The optical transmitting device according to claim 1, wherein the wavelength division delay and pre-emphasis module (5) comprises a multi-wavelength optical pulse input port (51), a wavelength division delay branch (52), a power pre-emphasis branch (53), a wavelength combining branch (54), and an output port (55), the multi-wavelength optical pulse input port (51) is connected to the output end of the first optical fiber amplifier (4) through an optical fiber, and the wavelength division delay branch (52) is configured to sequentially delay and download optical pulses of respective wavelengths in the multi-wavelength composite optical pulse signal; the power pre-emphasis branch (53) is used for independently adjusting the power of the optical pulse with each wavelength downloaded by the wave-division delay branch (52); the wave combining branch (54) is used for sequentially uploading and combining the optical pulses with the wavelengths regulated by the power pre-emphasis branch (53) to synthesize a multi-wavelength quasi-continuous optical signal with pre-emphasized power; and the output port (55) is used for outputting the combined multi-wavelength quasi-continuous optical signal.
3. An optical transmitting device according to claim 2, wherein the wavelength-division delay branch (52) comprises N wavelength-division devices (521) and N-1 optical fiber delay loops (522) alternately arranged with the N wavelength-division devices (521), the power pre-emphasis branch (53) comprises N electrical variable optical attenuators (531), and the combining branch (54) comprises N combining devices (541), wherein the N wavelength-division devices (521) are connected with the N electrical variable optical attenuators (531) in a one-to-one correspondence, and the N electrical variable optical attenuators (531) are connected with the N combining devices (541) in a one-to-one correspondence.
4. A light emitting arrangement according to claim 3, wherein the wave splitting device (521) comprises a broadband input port, a narrowband optical drop port and a broadband output port, the electrically variable optical attenuator (531) comprises an attenuation input port and an attenuation output port, and the wave combining device (541) comprises a wave combining input port, a narrowband optical drop port and a wave combining output port; wherein, the narrow-band optical down-load port of the ith wave-splitting device (521) is connected with the attenuation input port of the ith electric variable optical attenuator (531) through an optical fiber, and the attenuation output port of the ith electric variable optical attenuator (531) is connected with the narrow-band optical up-load port of the ith wave-combining device (541) through an optical fiber; the broadband output port of the ith wave splitting device (521) is connected with the broadband input port of the (i + 1) th wave splitting device (521) through the ith optical fiber delay ring (522), and the wave combining output port of the ith wave combining device (541) is connected with the wave combining input port of the (i + 1) th wave combining device (541) through an optical fiber; i is a positive integer greater than or equal to 1 and less than N.
5. An optical transmitting device as claimed in claim 3, wherein the broadband input port of the 1 st said wavelength division device (521) is connected to the input port (51) of the multi-wavelength optical pulse by an optical fiber, and the wavelength combining output port of the nth said wavelength combining device (541) is connected to the output port (55) by an optical fiber.
6. The optical transmitting device according to claim 2, wherein adjacent ones of the wave-splitting devices (521) of the wave-splitting delay branches (52) are connected by the optical fiber delay loop (522).
7. The optical transmitting device according to claim 2, wherein the lengths D of the delay fibers between two adjacent wave-splitting devices (521) in the wave-splitting delay branches (52) are the same:
wherein c is the speed of light in vacuum, T is the period of light pulse, N is the refractive index of the delay optical fiber, M is the number of time division multiplexing channels of the optical fiber hydrophone array, and min (M, N) is the minimum value of M and N.
8. The light emitting device according to claim 1, wherein the acousto-optic modulator assembly (3) is driven by a TTL level.
9. The optical transmission apparatus according to claim 1, wherein the duty cycle of the multi-wavelength optical pulse signal outputted from the acousto-optic modulator module (3) is less than or equal to 1/M, where M is the number of time division multiplexing channels of the optical fiber hydrophone array.
10. Optical transmission apparatus according to claim 1, wherein said first fiber amplifier (4) is an erbium doped fiber amplifier and said second fiber amplifier (6) is an erbium doped fiber amplifier.
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