CN108683453A - A kind of linear direct detection method and system based on synthesis single sideband singal - Google Patents
A kind of linear direct detection method and system based on synthesis single sideband singal Download PDFInfo
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- CN108683453A CN108683453A CN201810346891.4A CN201810346891A CN108683453A CN 108683453 A CN108683453 A CN 108683453A CN 201810346891 A CN201810346891 A CN 201810346891A CN 108683453 A CN108683453 A CN 108683453A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07953—Monitoring or measuring OSNR, BER or Q
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07955—Monitoring or measuring power
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6165—Estimation of the phase of the received optical signal, phase error estimation or phase error correction
Abstract
The invention discloses a kind of linear direct detection method and systems of optical signal based on synthesis single sideband singal.The system includes local oscillator laser, coupler, optical detector, radio frequency amplifier, electrical filter, analog-digital converter (ADC) and digital signal processor (DSP).Local oscillator laser frequency is arranged in incident optical signal frequency spectrum one side edge, and inputs optical detector by forming single sideband singal after coupler and incident optical signal multiplex.The analog signal of optical detector output is converted to digital signal after amplification filters by ADC.DSP will input digital signal as real part, and Hilbert transformation is added to obtain the complex signal for representing synthesized single sideband signals light field as imaginary part, and then restores incident optical signal light field by frequency deviation backoff algorithm.The relevant detection of digitlization of incident optical signal light field can be realized using single optical detector and single ADC by the present invention, have it is simple in structure, it is at low cost, the advantages that small power consumption.
Description
Technical field
The invention belongs to fiber optic communication, free space optical communication, optical signal detecting and digital processing fields, more specifically
Ground is related to a kind of linear direct detection method and system based on synthesis single sideband singal.
Background technology
Optical communication system mainly uses intensity modulated and Direct Inspection Technology at present.Light-receiving based on Direct Inspection Technology
Machine converts optical signals to electric signal using single photodiode, simple in structure, at low cost, but photodiode output current
It is directly proportional to square (i.e. the luminous power) of input optical signal mould field, therefore the strength information of signal light can only be detected.Due to intensity
The modulated dimension of whole of light field is modulated and underuses, therefore transmission efficiency is low, it is difficult to it is big to meet growing high speed
The demand of capacity communication system.Relevant detection can detect intensity, frequency, phase and each dimensional information of polarization of signal light,
With higher efficiency of transmission and sensitivity.It is restored to electric signal since the light field in detection that is concerned with can be linearized, is
A kind of linearisation detection technique.And the relevant detection of digitlization can be in numeric field recovering signal light field, and then algorithm can be passed through
Realize carrier synchronization, without complicated Optical phase-locked loop and high-performance laser, therefore high-speed high capacity long-distance optical communication at present
System mostly uses the coherent optical heterodyne communicatio based on digitlization coherent detection technology.But such coherent optical heterodyne communicatio generally wraps at present
2 optical mixer units are included, (each photo-equilibrium detector includes 2 photodiodes to 4 photo-equilibrium detectors, needs 8 light in total
Electric diode) and 4 analog-digital converters (Analog-to-Digital Converter, ADC), complicated, cost and work(
Consumption is all very high, is not suitable for data center, the occasion and satellite, sky more sensitive to cost such as Metropolitan Area Network (MAN) and Optical Access Network
Between the occasion harsh to communication terminal volume power consumption requirements such as stand, thus limit the coverage area of high-speed high capacity optical-fiber network.
Nearest foreign study person proposes some novel so-called " digital linearization " technologies.The technology is examined using single photodiode
It is flat to eliminate photodiode by Digital Signal Processing (Digital Signal Processing, DSP) operation for light signal
The nonlinear crosstalk that square rate receptance function introduces realizes the relevant detection of the linear digital of signal light field.The program can be significantly
System cost and power consumption are reduced, is a kind of digitlization coherence detection of green low cost.
" digital linearization " technology proposed at present includes mainly single-stage and two-stage linearisation filtering technique, iterative linearized
Filtering technique, signal and signal beat frequency interference cancellation techniques and this five kinds of linearization technique based on minimum phase signal.Before
Four kinds of technologies are after coming out nonlinear terms caused by single photodiode square law receptance function as a kind of distortion computation
It is subtracted from output signal again.Linearization technique based on minimum phase signal is minimum with signal light synthesizing optical using direct current light
Phase signal, and then its intensity size is detected using single photodiode, it is finally based on minimum phase signal amplitude in dsp
With Hilbert transformation relations reconstruction signal light field existing for phasetophase, spectrum efficiency and quality of output signals four kinds of skills earlier above
Art higher.But currently based on the linearization technique of minimum phase signal, there is also some disadvantages, such as DSP is in reconstruct light field letter
There are video stretching effects in logarithm operation when breath, and ADC is caused to be not enough to restore whole audience letter under conventional 2 times of sampling multiplying power
It ceases (at least needing 3 sampling multiplying powers), it is additional huge to that can bring if conventional 2 times to reduce sampling multiplying power to introduce iterative algorithm
Intensive proposes the rate of DSP data processings high requirement.
Invention content
For the disadvantages described above or Improvement requirement of the prior art, the present invention provides a kind of based on synthesis single sideband singal
Linear direct detection method and system, thus solves existing for the current linearization technique based on minimum phase signal to ADC
Sampling multiplying power demand is high, requires the data processing rate of DSP high technical problem.
To achieve the above object, according to one aspect of the present invention, a kind of line based on synthesis single sideband singal is provided
Property direct detection system, including：The local oscillator laser that is sequentially connected, coupler, optical detector, radio frequency amplifier, electrical filter,
Analog-digital converter and digital signal processor；
Wherein, it includes defeated with 1 that the coupler, which has 2 input ports and 2 output ports, the optical detector,
The common optical detector PD of inbound port and 1 output port, or the photo-equilibrium with 2 input ports and 1 output port
Detector BPD, the coupler 1 that 1 port and the common optical detector PD are arbitrarily chosen from 2 output ports are defeated
Inbound port connects or 2 output ports are connect by the coupler with 2 input ports of the photo-equilibrium detector BPD；
The local oscillator laser is used to provide the local oscillator optical signal for carrying out beat frequency with incident optical signal, wherein the local oscillator
The frequency of optical signal is located in the left or right side preset range of the frequency spectrum of the incident optical signal；
The coupler obtains two-way satisfaction list for the incident optical signal and the local oscillator optical signal to be carried out multiplex
The optical signal of sideband condition；
The optical detector, for after multiplex incident optical signal and local oscillator optical signal be converted to rf signal all the way；
The radio frequency amplifier is met for amplifying the rf signal for coming from the optical detector with reaching
The demand of the analog-digital converter sampled level；
The electrical filter, for filtering out the noise in amplified rf signal；
The analog-digital converter is converted to digital signal for will filter out the rf signal after noise；
The digital signal processor, for handling the digital signal inputted by the analog-digital converter,
To restore signal light field in numeric field, digital coherent detection is realized.
Wherein, local oscillator optical signal can be generated in transmitting terminal, and be transmitted to receiving terminal after incident optical signal multiplex, can also connect
Receiving end generates, and is input to optical detector after coupler multiplex with the incident optical signal for being transmitted to receiving terminal.
Preferably, if the optical detector is common optical detector PD, the rf signal is：The digital signal is：
Wherein, IPD(t) table
Show the rf signal, RPDIndicate the responsiveness of the common optical detector PD, PSIndicate the light work(of the incident optical signal
Rate, PLOIndicate the luminous power of the local oscillator optical signal, ωIFThe angular frequency and the local oscillator light for indicating the incident optical signal are believed
Number angular frequency it is poor, φSIndicate the phase information that the incident optical signal carries, Idig-PD(nT) digital signal, T are indicated
Indicate that the sampling interval duration of the digital signal processor, n indicate sampled point serial number.
Preferably, the digital signal processor, for by Iim-PD(nT)=HT [Idig-PD(nT)]
Hilbert is carried out to the digital signal to convert to obtain new digital signal Iim-PD(nT), byRestore signal light field in numeric field, realizes number
The relevant detection of word, wherein Iim-PD(nT) corresponding ES-PD(nT) sampled value of the imaginary part amplitude size of field information, HT are indicated
Hilbert is converted,For signal Idig-PD(nT) mean value.
Preferably, if the optical detector is photo-equilibrium detector BPD, the rf signal is：The digital signal is：
Wherein, IBPD(t) radio frequency electrical is indicated
Signal, RBPDIndicate the responsiveness of the photo-equilibrium detector BPD, PSIndicate the luminous power of the incident optical signal, PLOIndicate institute
State the luminous power of local oscillator optical signal, ωIFIndicate that the angular frequency of the angular frequency and the local oscillator optical signal of the incident optical signal is poor,
φSIndicate the phase information that the incident optical signal carries, Idig-BPD(nT) indicate that the digital signal, T indicate the number letter
The sampling interval duration of number processor, n indicate sampled point serial number.
Preferably, if the optical detector is the photo-equilibrium detector BPD, the digital signal processor is used for
By Iim-BPD(nT)=HT [Idig-BPD(nT)] Hilbert is carried out to the digital signal to convert to obtain new digital signal Iim-BPD
(nT), by ES-BPD(nT)=Idig-BPD(nT)+j[Iim-BPD(nT)] restore signal light field in numeric field, realize digital coherent inspection
It surveys, wherein Iim-BPD(nT) corresponding ES-BPD(nT) sampled value of the imaginary part amplitude size of field information, HT indicate that Hilbert becomes
It changes.
Wherein, the amplification factor of the radio frequency amplifier should be with the nominal input voltage dynamic range of the analog-digital converter
Match.
It is another aspect of this invention to provide that a kind of linear direct detection method based on synthesis single sideband singal is provided,
Including：
Incident optical signal and local oscillator optical signal are obtained into the optical signal that two-way meets unilateral conditional by multiplex, and will be closed
Incident optical signal and local oscillator optical signal after wave are converted to rf signal all the way, wherein the frequency position of the local oscillator optical signal
In the left or right side edge of the frequency spectrum of the incident optical signal；
The rf signal is amplified, to reach the demand for meeting analog-to-digital conversion sampled level, and filters out amplification
The noise in rf signal afterwards；
The rf signal after noise will be filtered out and be converted to digital signal, and the digital signal is handled, with
Numeric field restores signal light field, realizes digital coherent detection.
Wherein, local oscillator optical signal can be according to actual demand flexible configuration in transmitting terminal or receiving terminal.Local oscillator optical signal is being sent out
When penetrating end and generating, through optical fiber or space propagation to receiving terminal after incident optical signal and local oscillator optical signal multiplex.Local oscillator optical signal
When receiving terminal generates and with the incident optical signal for being transmitted to receiving terminal optical detector is input to after coupler multiplex.
Preferably, described that incident optical signal and local oscillator optical signal are obtained into two ways of optical signals by multiplex, and by described two
Road optical signal is converted to rf signal all the way, including：
By the incident optical signal and the local oscillator optical signal by coupler multiplex at two-way incident optical signal after, by institute
The arbitrary optical signal all the way stated in two-way incident optical signal is converted to rf signal all the way by common optical detector PD, or
The two ways of optical signals is converted to rf signal all the way by person by photo-equilibrium detector BPD.
It preferably, if will be in the two-way incident optical signal by the common optical detector PD
Arbitrarily optical signal is converted to rf signal all the way all the way, and the rf signal is：The digital signal is：Wherein, IPD(t) institute is indicated
State rf signal, RPDIndicate the responsiveness of the common optical detector PD, PSIndicate the luminous power of the incident optical signal, PLO
Indicate the luminous power of the local oscillator optical signal, ωIFIndicate the angle of the angular frequency and the local oscillator optical signal of the incident optical signal
Difference on the frequency, φSIndicate the phase information that the incident optical signal carries, Idig-PD(nT) indicate the digital signal, T indicate into
Sampling interval duration when row Digital Signal Processing, n indicate sampled point serial number.
Preferably, described that the digital signal is handled, to restore signal light field in numeric field, realize digital coherent
Detection includes：
By Iim-PD(nT)=HT [Idig-PD(nT)] Hilbert is carried out to the digital signal to convert to obtain new number letter
Number Iim-PD(nT), byRestore to believe in numeric field
Number light field realizes digital coherent detection, wherein Iim-PD(nT) corresponding ES-PD(nT) sampling of the imaginary part amplitude size of field information
Value, HT indicate Hilbert transformation,For signal Idig-PD(nT) mean value.
Preferably, if the two-way incident optical signal is converted to radio frequency electrical all the way by the photo-equilibrium detector BPD
Signal, then the rf signal be：The digital signal is：Wherein, IBPD(t) rf signal is indicated,
RBPDIndicate the responsiveness of the photo-equilibrium detector BPD, PSIndicate the luminous power of the incident optical signal, PLOIndicate described
It shakes the luminous power of optical signal, ωIFIndicate that the angular frequency of the angular frequency and the local oscillator optical signal of the incident optical signal is poor, φS
Indicate the phase information that the incident optical signal carries, Idig-BPD(nT) indicate that the digital signal, T indicate to carry out digital signal
Sampling interval duration when processing, n indicate sampled point serial number.
Preferably, described that the digital signal is handled, to restore signal light field in numeric field, realize digital coherent
Detection includes：
By Iim-BPD(nT)=HT [Idig-BPD(nT)] Hilbert is carried out to the digital signal to convert to obtain new number
Signal Iim-BPD(nT), by ES-BPD(nT)=Idig-BPD(nT)+j[Iim-BPD(nT)] restore signal light field in numeric field, realize number
The relevant detection of word, wherein Iim-BPD(nT) corresponding ES-BPD(nT) sampled value of the imaginary part amplitude size of field information, HT are indicated
Hilbert is converted.
In general, through the invention it is contemplated above technical scheme is compared with the prior art, can obtain down and show
Beneficial effect：
(1) local oscillator laser, coupler, optical detector (PD or BPD) is used only in digital coherent detecting system of the invention,
Radio frequency amplifier, electrical filter, analog-digital converter ADC and each one of digital signal processor DSP.Compared to previous digital phase
Dry photoreceiver, required optical detector, ADC and DSP quantity are greatly reduced, and are not necessarily to optical mixer unit, therefore system structure letter
Single, good reliability is at low cost, small power consumption.
(2) the linear direct detection system constituted using common optical detector PD is compared currently based on minimum phase signal
Linear direct detection system for, the present invention is by the linear direct detection method based on synthesis single sideband singal to significantly
The complexity and operand for reducing demodulating algorithm make the present invention that can substantially reduce the arithmetic speed requirement of DSP, while this hair
Bright demodulating algorithm, which avoids logarithm operation etc., can lead to the algorithm of video stretching, reduce the high demand that bandwidth is sampled to ADC,
It is very suitable for data center, the occasion and satellite, space station etc. more sensitive to cost such as Metropolitan Area Network (MAN) and Optical Access Network
The occasion harsh to communication terminal volume power consumption requirements, can greatly improve the coverage area of high-speed high capacity optical-fiber network.
(3) it uses the linear direct detection system that photo-equilibrium detector BPD is constituted to compare currently based on minimum phase to believe
Number linear direct detection system for, in addition to have the advantages that (2) it is inner it is described other than, be also greatly reduced to local oscillation optical power
Demand.The present invention eliminates relative intensity noise caused by signal light and local oscillator light by balance detection structure simultaneously
(Relative intensity noise, RIN), improves the signal-to-noise ratio of output rf signal, and the present invention also passes through pairing
Two ways of optical signals after wave carries out the problem of opto-electronic conversion avoids multiplex optical power loss, is very suitable for clever using superelevation is pursued
Sensitivity and ultrahigh energy efficiency than occasion, while it is harsh to communication terminal volume power consumption requirements to be also applied for satellite, space station etc.
Occasion can greatly improve communication distance and improve communication quality.
Description of the drawings
Fig. 1 is a kind of structure of linear direct detection system based on synthesis single sideband singal provided in an embodiment of the present invention
Schematic diagram；
Fig. 2 is that one kind provided in an embodiment of the present invention is based on the present invention and currently based on minimum phase under typical case environment
The signal that the linear direct detection system of position signal and traditional phase diversity coherent optical heterodyne communicatio based on optical mixer unit are exported
Quality (being indicated with Error Vector Magnitude EVM) is with the change curve of input signal OSNR；
Fig. 3 is provided in an embodiment of the present invention a kind of under conditions of fixed signal input power (- 40dBm), based on this
Invention and the linear direct detection system based on minimum phase signal and traditional phase diversity coherent light based on optical mixer unit connect
Receipts machine quality of output signals (being indicated with Error Vector Magnitude EVM) (uses P with the direct current light being added with signal light power ratioLO/
PsIndicate) change curve；
In all the appended drawings, identical reference numeral is used for indicating identical element or structure, wherein：
1- local oscillator lasers, 2- couplers, 3- optical detectors, 4- radio frequency amplifiers, 5- electrical filters, 6- analog-digital converters
ADC, 7- digital signal processor DSP.
Specific implementation mode
In order to make the purpose , technical scheme and advantage of the present invention be clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
It does not constitute a conflict with each other and can be combined with each other.
The present invention provides a kind of linear direct detection method and systems based on synthesis single sideband singal, thus solve mesh
To ADC sampling multiplying power demands height, to the data processing rate of DSP existing for the preceding linearization technique based on minimum phase signal
It is required that high technical problem.
It is a kind of linear direct detection system based on synthesis single sideband singal provided in an embodiment of the present invention as shown in Figure 1
Structural schematic diagram, include in the system shown in figure 1：The local oscillator laser 1 that is sequentially connected, optical detector 3, is penetrated coupler 2
Audio amplifier 4, electrical filter 5, analog-digital converter 6, digital signal processor 7；
Wherein, optical detector can use common optical detector (Photodetector, PD), have 1 input port and
1 output port；Photo-equilibrium detector (Balanced Photo-detector, BPD) can also be used, there are 2 input terminals
Mouth and 1 output port.
In embodiments of the present invention, the frequency of local oscillator optical signal be located at the frequency spectrum of incident optical signal left or right side it is default
In range, wherein preset range can be determined according to actual use situation.
In embodiments of the present invention, local oscillator optical signal can be generated in transmitting terminal, and be transmitted to receiving terminal after photosynthetic wave signal；
Also it can be generated in receiving terminal, and optical detector is input to after coupler multiplex with the incoming signal light for being transmitted to receiving terminal.
In embodiments of the present invention, incident optical signalWith local oscillator optical signalIt obtains being input to optical detector after two-way meets the optical signal of unilateral conditional through coupler multiplex
1 or 2 input ports (being judged according to the input port quantity variance of PD and BPD), wherein Ps、PLORespectively incident optical signal
With the luminous power of local oscillator optical signal, ωS、ωLORespectively incident optical signal and the corresponding angular frequency of local oscillator optical signal, φS(t) it is
The phase information that incident optical signal carries.
Optical detector, for converting 1 tunnel or 2 road optical signals (judging according to the input port quantity variance of PD and BPD)
For 1 road rf signal；
When in embodiments of the present invention, using common optical detector PD, rf signal (does not consider that multiplex luminous power is damaged
Lose) be：When using photo-equilibrium detector BPD,
Rf signal is：Wherein, IPD(t) or IBPD(t) radio frequency electrical is indicated
Signal, RPDIndicate the responsiveness of common optical detector PD, RBPDIndicate the responsiveness of photo-equilibrium detector BPD, PSIndicate incident light
The luminous power of signal, PLOIndicate the luminous power of local oscillator optical signal, ωIFIndicate the angular frequency and local oscillator optical signal of incident optical signal
Angular frequency it is poor, φSIndicate the phase information that incident optical signal carries.
Radio frequency amplifier meets analog-digital converter and adopts for amplifying the rf signal for coming from optical detector to reach
The demand of sample level；
Wherein, the amplification factor of radio frequency amplifier should match with the nominal input voltage dynamic range of analog-digital converter.
Electrical filter, for filtering out the noise in amplified rf signal；
Analog-digital converter is converted to digital signal for will filter out the rf signal after noise；
When in embodiments of the present invention, using common optical detector PD, digital signal is：Use photo-equilibrium detector
When BPD, digital signal is：Wherein, Idig-PD
(nT) or Idig-BPD(nT) indicate that digital signal, T indicate that the sampling interval duration of digital signal processor, n indicate sampled point sequence
Number.
Digital signal processor, for handling the digital signal inputted by analog-digital converter, with extensive in numeric field
Complex signal light field realizes digital coherent detection.
When in embodiments of the present invention, using common optical detector PD, digital signal processor, for by Iim-PD(nT)=
HT[Idig-PD(nT)] Hilbert is carried out to digital signal to convert to obtain new digital signal Iim-PD(nT), byRestore signal light field in numeric field, realizes number
The relevant detection of word, wherein Iim-PD(nT) corresponding ES-PD(nT) sampled value of the imaginary part amplitude size of field information, HT are indicated
Hilbert is converted,For signal Idig-PD(nT) mean value.
When using photo-equilibrium detector BPD, digital signal processor, for by Iim-BPD(nT)=HT [Idig-BPD
(nT)] Hilbert is carried out to digital signal to convert to obtain new digital signal Iim-BPD(nT), by ES-BPD(nT)=Idig-BPD
(nT)+j[Iim-BPD(nT)] restore signal light field in numeric field, realize digital coherent detection, wherein Iim-BPD(nT) corresponding ES-BPD
(nT) sampled value of the imaginary part amplitude size of field information, HT indicate Hilbert transformation.
The present invention also provides a kind of linear direct detection methods based on synthesis single sideband singal, including：
Incident optical signal and local oscillator optical signal are obtained into the optical signal that two-way meets unilateral conditional by multiplex, and will be closed
Incident optical signal and local oscillator optical signal after wave are converted to rf signal all the way, wherein the frequency of local oscillator optical signal be located at into
It penetrates in the left or right side preset range of the frequency spectrum of optical signal, wherein preset range can carry out true according to actual use situation
It is fixed；
Rf signal is amplified, to reach the demand for meeting analog-to-digital conversion sampled level, and is filtered out amplified
Noise in rf signal；
The rf signal after noise will be filtered out and be converted to digital signal, and digital signal is handled, in number
Signal light field is restored in domain, realizes digital coherent detection.
Fig. 2 be typical case environment under based on the present invention and currently based on minimum phase signal linear direct detection system
And the signal quality that traditional phase diversity coherent light receiving system based on optical mixer unit is exported (uses Error Vector Magnitude EVM
Indicate) with the change curve of input optical signal OSNR.Wherein, the optical signal detected is 20Gbps (baud rate 10GBaud/
S) quadrature phase shift keying (QPSK) signal.The BER=1e as EVM=32.5%-3.Work as EVM=32.5% as can be seen from Figure 2
That is BER=1e-3When, based on the present invention linear direct detection system using common optical detector PD when sensitivity at present
Linear direct detection system based on minimum phase signal is suitable；Linear direct detection system based on the present invention is flat using light
Sensitivity when weighing apparatus detector BPD improves 1.1dB relative to currently based on the linear direct detection system of minimum phase signal
(required OSNR reduces 1.1dB), with the highest traditional phase diversity coherent optical heterodyne communicatio based on optical mixer unit of current sensitivity
It compares, sensitivity is consistent.
Fig. 3 is shown under conditions of fixed signal input power (- 40dBm), is believed based on the present invention and based on minimum phase
Number linear direct detection system and tradition based on optical mixer unit phase diversity coherent light receiving system quality of output signals (use
Error Vector Magnitude EVM is indicated) with the local oscillator light being added (P is used with signal light power ratioLO/PsIndicate) change curve.
As can be seen from Figure 3 as EVM=32.5%, that is, BER=1e under same operating condition-3When the technology of the present invention using common
Required DC optical power P when optical detector PDLO=30Ps, compared to based on minimum phase signal linearization technique (PLO=8Ps)
Though local oscillation optical power demand is improved, because the reduction of sampling bandwidth demand and algorithm complexity makes system synthesis originally drop significantly
It is low.In practical applications, because the power of incident optical signal is more faint, therefore under the premise of ensureing comparable receptivity,
There is great practicability and economic value system cost is greatly reduced by improving local oscillation optical power.The technology of the present invention simultaneously
Required DC optical power P when using photo-equilibrium detector BPDLO=2Ps, compared to based on minimum phase signal linearization technique
(PLO=8Ps) 4 times are reduced, at this time for using common optical detector (PD), though system cost is slightly improved,
Significantly being promoted for receptivity and being greatly lowered for local oscillation optical power demand are obtained, the comprehensive performance and biography of the present invention are made
Phase diversity coherent light receiving system of the system based on optical mixer unit is consistent.
In short, the present invention using common optical detector PD when relative to the linear direct detection based on minimum phase signal
System has system cost lower, and algorithm complexity is lower, the better advantage of stability；The present invention is using photo-equilibrium detector
There is when BPD compared with the linear direct detection system based on minimum phase signal higher sensitivity, lower local oscillator
Light power requirements, lower algorithm complexity and better system stability.Simultaneously with phase of the tradition based on optical mixer unit
Diversity coherent light receiving system is compared, under conditions of considerably reducing system cost, obtain identical receptivity and
Systematic energy efficiency ratio.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, all within the spirits and principles of the present invention made by all any modification, equivalent and improvement etc., should all include
Within protection scope of the present invention.
Claims (10)
1. a kind of linear direct detection system based on synthesis single sideband singal, which is characterized in that including：The local oscillator being sequentially connected
Laser, coupler, optical detector, radio frequency amplifier, electrical filter, analog-digital converter and digital signal processor；
Wherein, it includes having 1 input terminal that the coupler, which has 2 input ports and 2 output ports, the optical detector,
The common optical detector PD of mouth and 1 output port, or the detection of the photo-equilibrium with 2 input ports and 1 output port
Device BPD, the coupler arbitrarily choose 1 input terminal of 1 port and the common optical detector PD from 2 output ports
2 output ports are connect by mouth connection or the coupler with 2 input ports of the photo-equilibrium detector BPD；
The local oscillator laser, for providing the local oscillator optical signal for carrying out beat frequency with incident optical signal, wherein the local oscillator light letter
Number the frequency frequency spectrum that is located at the incident optical signal left or right side preset range in；
The coupler, for obtaining two-way and meeting single-side belt the incident optical signal and local oscillator optical signal progress multiplex
The optical signal of condition；
The optical detector, for by after multiplex incident optical signal and local oscillator optical signal be converted to rf signal all the way；
The radio frequency amplifier, for amplifying the rf signal for coming from the optical detector, with reach meet it is described
The demand of analog-digital converter sampled level；
The electrical filter, for filtering out the noise in amplified rf signal；
The analog-digital converter is converted to digital signal for will filter out the rf signal after noise；
The digital signal processor, for handling the digital signal inputted by the analog-digital converter, with
Numeric field restores signal light field, realizes digital coherent detection.
2. system according to claim 1, which is characterized in that described if the optical detector is common optical detector PD
Rf signal is：The digital signal
For：Wherein, IPD(t) it indicates
The rf signal, RPDIndicate the responsiveness of the common optical detector PD, PSIndicate the luminous power of the incident optical signal,
PLOIndicate the luminous power of the local oscillator optical signal, ωIFIndicate the angular frequency of the incident optical signal and the local oscillator optical signal
Angular frequency is poor, φSIndicate the phase information that the incident optical signal carries, Idig-PD(nT) indicate that the digital signal, T indicate
The sampling interval duration of the digital signal processor, n indicate sampled point serial number.
3. system according to claim 2, which is characterized in that the digital signal processor, for by Iim-PD(nT)=
HT[Idig-PD(nT)] Hilbert is carried out to the digital signal to convert to obtain new digital signal Iim-PD(nT), byRestore signal light field in numeric field, realizes number
The relevant detection of word, wherein Iim-PD(nT) corresponding ES-PD(nT) sampled value of the imaginary part amplitude size of field information, HT are indicated
Hilbert is converted,For signal Idig-PD(nT) mean value.
4. system according to claim 1, which is characterized in that if the optical detector is photo-equilibrium detector
BPD, then the rf signal be：The digital signal is：Wherein, IBPD(t) rf signal is indicated,
RBPDIndicate the responsiveness of the photo-equilibrium detector BPD, PSIndicate the luminous power of the incident optical signal, PLOIndicate described
It shakes the luminous power of optical signal, ωIFIndicate that the angular frequency of the angular frequency and the local oscillator optical signal of the incident optical signal is poor, φS
Indicate the phase information that the incident optical signal carries, Idig-BPD(nT) indicate that the digital signal, T indicate the digital signal
The sampling interval duration of processor, n indicate sampled point serial number.
5. system according to claim 4, which is characterized in that the digital signal processor, for by Iim-BPD(nT)=
HT[Idig-BPD(nT)] Hilbert is carried out to the digital signal to convert to obtain new digital signal Iim-BPD(nT), by ES-BPD
(nT)=Idig-BPD(nT)+j[Iim-BPD(nT)] restore signal light field in numeric field, realize digital coherent detection, wherein Iim-BPD
(nT) corresponding ES-BPD(nT) sampled value of the imaginary part amplitude size of field information, HT indicate Hilbert transformation.
6. a kind of linear direct detection method based on synthesis single sideband singal, which is characterized in that including：
Incident optical signal and local oscillator optical signal are obtained into the optical signal that two-way meets unilateral conditional by multiplex, and will be after multiplex
Incident optical signal and local oscillator optical signal be converted to rf signal all the way, wherein the frequency of the local oscillator optical signal is located at institute
It states in the left or right side preset range of the frequency spectrum of incident optical signal；
The rf signal is amplified, to reach the demand for meeting analog-to-digital conversion sampled level, and is filtered out amplified
Noise in rf signal；
The rf signal after noise will be filtered out and be converted to digital signal, and the digital signal is handled, in number
Signal light field is restored in domain, realizes digital coherent detection.
7. according to the method described in claim 6, it is characterized in that, described pass through multiplex by incident optical signal and local oscillator optical signal
Two ways of optical signals is obtained, and the two ways of optical signals is converted into rf signal all the way, including：
By the incident optical signal and the local oscillator optical signal by coupler multiplex at two-way incident optical signal after, by described two
Arbitrary optical signal all the way in the incident optical signal of road is converted to rf signal all the way by common optical detector PD, alternatively, will
The two ways of optical signals is converted to rf signal all the way by photo-equilibrium detector BPD.
8. if the method according to the description of claim 7 is characterized in that will be described by the common optical detector PD
Arbitrary optical signal all the way in two-way incident optical signal is converted to rf signal all the way, and the rf signal is：The digital signal is：Wherein, IPD(t) institute is indicated
State rf signal, RPDIndicate the responsiveness of the common optical detector PD, PSIndicate the luminous power of the incident optical signal, PLO
Indicate the luminous power of the local oscillator optical signal, ωIFIndicate the angle of the angular frequency and the local oscillator optical signal of the incident optical signal
Difference on the frequency, φSIndicate the phase information that the incident optical signal carries, Idig-PD(nT) indicate the digital signal, T indicate into
Sampling interval duration when row Digital Signal Processing, n indicate sampled point serial number.
9. according to the method described in claim 8, it is characterized in that, described handle the digital signal, in number
Signal light field is restored in domain, realizes that digital coherent detection includes：
By Iim-PD(nT)=HT [Idig-PD(nT)] Hilbert is carried out to the digital signal to convert to obtain new digital signal
Iim-PD(nT), byRestore signal in numeric field
Light field realizes digital coherent detection, wherein Iim-PD(nT) corresponding ES-PD(nT) sampling of the imaginary part amplitude size of field information
Value, HT indicate Hilbert transformation,For signal Idig-PD(nT) mean value.
10. if the method according to the description of claim 7 is characterized in that pass through the photo-equilibrium detector BPD
The two-way incident optical signal is converted into rf signal all the way, then the rf signal is：The digital signal is：
Wherein, IBPD(t) the radio frequency telecommunications is indicated
Number, RBPDIndicate the responsiveness of the photo-equilibrium detector BPD, PSIndicate the luminous power of the incident optical signal, PLODescribed in expression
The luminous power of local oscillator optical signal, ωIFIndicate that the angular frequency of the angular frequency and the local oscillator optical signal of the incident optical signal is poor,
φSIndicate the phase information that the incident optical signal carries, Idig-BPD(nT) indicate that the digital signal, T indicate to carry out digital letter
Number processing when sampling interval duration, n indicate sampled point serial number；
It is described that the digital signal is handled, to restore signal light field in numeric field, realize that digital coherent detection includes：
By Iim-BPD(nT)=HT [Idig-BPD(nT)] Hilbert is carried out to the digital signal to convert to obtain new digital signal
Iim-BPD(nT), by ES-BPD(nT)=Idig-BPD(nT)+j[Iim-BPD(nT)] restore signal light field in numeric field, realize digital phase
Dry detection, wherein Iim-BPD(nT) corresponding ES-BPD(nT) sampled value of the imaginary part amplitude size of field information, HT indicate Hilbert
Transformation.
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