CN101588206B - Device and method for locking optical signal frequency by demodulator in DPSK system - Google Patents
Device and method for locking optical signal frequency by demodulator in DPSK system Download PDFInfo
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- CN101588206B CN101588206B CN2008100673504A CN200810067350A CN101588206B CN 101588206 B CN101588206 B CN 101588206B CN 2008100673504 A CN2008100673504 A CN 2008100673504A CN 200810067350 A CN200810067350 A CN 200810067350A CN 101588206 B CN101588206 B CN 101588206B
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Abstract
The invention relates to a device for locking an optical signal frequency by a demodulator in a DPSK system, which comprises a DPSK sending unit, a transmission link and a DPSK receiving unit, whereinthe DPSK receiving unit comprises a demodulator, a balanced receiver, a microprocessing unit, a demodulator adjusting circuit, a signal restoring unit, a first current monitoring unit and a second cu rrent monitoring unit; the invention also provides a method for the locking the optical signal frequency by the demodulator in the DPSK system, which comprises the following steps: generating a bit sequence of specific patterns through the DPSK sending unit, sending the bit sequence to the DPSK receiving unit, acquiring a current monitoring value from the DPSK receiving unit, normalizing the current monitoring value through the microprocessing unit, finding the maximum current value, and finally locking the optical signal frequency. The invention avoids a faulty adjustment effect of the demodulator caused by input optical power change and detection current pattern change, realizes the optical signal frequency locking by the demodulator, and optimizes the receiving performance of the DPSK system.
Description
Technical field
The present invention relates to optical communication field, (Differential Phase Shift Keying DPSK) utilizes the apparatus and method of demodulator locks optical signal frequency in the system to relate in particular to differential phase keying (DPSK) in the WDM.
Background technology
New type of modulation sign indicating number type based on the phase modulated principle is more superior than traditional sign indicating number type based on intensity modulated, has obtained extensive studies and application at present in high speed, long haul optical transmission.Phase modulation technique is realized the reception of signal by coherent demodulation and two kinds of methods of direct probe method (also claiming from coherent demodulation).Wherein, coherent demodulation realizes complicated, and direct probe method is simple relatively.Direct probe method at first utilizes delay interferometer, and (Delay-Interferometer DI) as demodulator (Demodulator), and then utilizes balanced reciver to realize the recovery of signal, sees Fig. 1.The direct probe method phase modulation format comprises DPSK modulation format, difference quadrature phase shift keying (Differential Quadrature Phase Shift Keying, DQPSK) modulation format.
The frequency drift of laser to the systematic function influence significantly in the DPSK system.Article " Optical Phase-Shift-Keyed Transmission " (JOURNAL OF LIGHTWAVETECHNOLOGY with reference to A.H.Gnauck, VOL.23, NO.1, JANUARY 2005), see Fig. 2, when the frequency drift 5% of laser, (Optical Signal to Noise Ratio, OSNR) cost is 2dB to the Optical Signal To Noise Ratio of system.Wavelength-division multiplex system with 40G DPSK is an example, if laser frequency drift 2GHz, the OSNR tolerance limit of system is with deterioration 2dB so.If the wavelength-division multiplex system of 10G DPSK, then laser frequency allows drift 200MHz.And the patient frequency drift of the wavelength-division multiplex system of DQPSK is littler.Even laser possesses the wavelength locking function, also between 1.5 ~ 3GHz, this is that institute of DPSK system is flagrant to its frequency maximum drift.And the demodulator wavelength also has temperature dependency, needs temperature control equally.When WDM beginning, also need to adjust the demodulator locks optical signal frequency.
As shown in Figure 3, from inserting on the loss spectra angle, demodulator is the optical filter of one-period, peak and Gu Caineng that signal frequency only works in optical filter reach optimum, we can say: in the channel wavelength scope, interfere the mutually long-armed band pass filter that is equivalent to, and interfere the arm that disappears mutually to be equivalent to band stop filter.Because the variation of the aging and ambient temperature of device, signal frequency is drifted about inevitably, and the filter wavelength of demodulator also might be drifted about.If the filter wavelength of demodulator is coincide all the time, so just the system injury that can avoid signal frequency drift to cause with signal frequency.
The wavelength of optical filter can be adjusted by temperature control, how to utilize the wavelength of adjusting demodulator to come the locking signal light frequency so people begin one's study.The article of E.A.Swanson " High sensitivityoptically preamplified direct detection DPSK receiver with activedelay-line stabilization " (IEEE Photon.Technol.Lett., vol.6, pp.263-265,1994.) tentatively solved this problem, it utilizes the electric current of one of them receiver of balanced reciver to adjust demodulator as feedback signal, thereby realizes the demodulator locks signal frequency.But, the input optical power of signal is variable, and especially on engineering, the electric current of balanced reciver also can change like this, and the distribution of signal 1 and signal 0 is relevant in the variation of electric current and the input signal sequence, adjusts mode so must seek more effective demodulator.
Chinese patent CN200710143877.6 " DPSK light modulation signal receiving device and method " has wherein also proposed a kind of method of how controlling demodulator, and with reference to figure 4, specifically, " peak detector is used to detect the peak value of the signal of telecommunication that is exaggerated; The time-delay control module is connected between optical fiber decoder and the peak detector, when peak detector detects peak value less than the signal of telecommunication that is amplified by limiting amplifier, and the time of delay of time-delay control module control optical fiber decoder ".This is that the electrical signal amplitude peak value is adjusted demodulator after utilizing opto-electronic conversion.
But the electric current of two detectors of balanced reciver is not changeless, can change with the variation of input optical power, and it is relevant with the pattern of input signal, as shown in the table, be the result of emulation, the luminous power of input signal remains unchanged, input signal is a pseudo random sequence, and the probability of signal 1 is 0.5, the each result of the electric current of two detectors (IPD1 and IPD2) is different in 10 emulation, and the electric current of also observing two detectors in experiment changes in time.
| No. | IPD1(a.u.) | IPD2(a.u.) |
| 1 | 0.4476752 | 0.5523248 |
| 2 | 0.5054028 | 0.4945972 |
| 3 | 0.4582242 | 0.5417758 |
| 4 | 0.4484064 | 0.5515936 |
| 5 | 0.4580571 | 0.5419429 |
| 6 | 0.4590076 | 0.5409924 |
| 7 | 0.4368441 | 0.5631559 |
| 8 | 0.4537645 | 0.5462355 |
| 9 | 0.4498475 | 0.5501525 |
| 10 | 0.4587255 | 0.5412745 |
European patent EP 1643665A1, " Control of delay line interferometer " proposed a kind ofly to utilize forward error correction (Forward Error Correction, FEC) error code information is adjusted the apparatus and method of demodulator.But it is consuming time to gather FEC error code information, and error code information is subjected to the various influences of optimizing and revising control ring of receiver very big, and the control algolithm more complicated should avoid using the adjustment control based on FEC error code information as far as possible.
Summary of the invention
Technical problem to be solved by this invention is, the device that utilizes the demodulator locks optical signal frequency in a kind of DPSK system is provided, and on the basis of this device, provide a kind of method of utilizing the demodulator locks optical signal frequency, the present invention to overcome the problem that the drift of optical signal frequency in the DPSK system causes system performance degradation.The present invention also adapts to and is applicable to DQPSK, and based on various improvement sign indicating number type, for example RZ-DPSK, RZ-DQPSK or the like of DPSK, DQPSK.
Utilize the device of demodulator locks optical signal frequency in a kind of DPSK system, comprise the DPSK transmitting element successively, transmission link, the DPSK receiving element, wherein the DPSK receiving element also comprises demodulator, balanced reciver, microprocessing unit, demodulator is adjusted circuit and signal recovery unit, demodulator is divided into 2 the tunnel with the light signal of input, enter balanced reciver, last entering signal recovery unit, the output current of microprocessing unit analyzing and processing balanced reciver, adjust circuit by demodulator and adjust demodulation filters wavelength adjustment parameter, this device also comprises first and second current monitoring unit, described first and second current detecting unit one end links to each other with one tunnel output of balanced reciver respectively, and an end links to each other with microprocessing unit.
Described first current detecting unit is a current detector.
Described second current detecting unit is a current detector.
A kind of method of utilizing the demodulator locks optical signal frequency may further comprise the steps:
Step 1: the DPSK transmitting element produces the bit sequence of specific pattern, enters the DPSK receiving element through transmission link;
Step 2: the DPSK receiving element is adjusted the filter wavelength of demodulator and is adjusted parameter, obtains the current monitoring value, sends to microprocessing unit;
Step 3: microprocessing unit carries out normalized to described current monitoring value, finds current maxima, and adjusts the filter wavelength adjustment parameter that circuit is adjusted demodulator, locking optical signal frequency by demodulator.
Described step 2 further may further comprise the steps:
Steps A: the DPSK receiving element is adjusted the filter wavelength of demodulator and is adjusted parameter, and the light signal of input is divided into two-way enters balanced reciver;
Step B: the current monitoring unit detects the output current of balanced reciver, and the current monitoring value that obtains is sent to microprocessing unit.
Described step 3 further may further comprise the steps:
Step a: microprocessing unit carries out normalized to the current value that receives, and obtains normalized current monitoring value;
Step b: normalized current monitoring value is carried out match, obtain matched curve, an intercepting part is wherein found out current maxima;
Step c: the order demodulator is adjusted the filter wavelength adjustment parameter that circuit is adjusted demodulator;
Steps d: demodulator is adjusted parameter adjustment to current maxima value corresponding, locking optical signal frequency with its filter wavelength.
Among the described step b, the normalization matched curve of intercepting comprises 1 peak value and 2 valleies.
Apparatus and method of the present invention compared with prior art, have avoided input optical power variation and detection electric current to put in order effect because of change in pattern causes the demodulator mistuning, have realized the demodulator locking optical signal frequency, have greatly optimized the receptivity of DPSK system.
Description of drawings
Fig. 1 is a DPSK system receiving element theory diagram;
Fig. 2 is the OSNR cost schematic diagram of DPSK system medium frequency mismatch;
Fig. 3 is the filter shape schematic diagram of the used demodulator of DPSK system;
Fig. 4 is traditional scheme 2 theory diagrams that DPSK system demodulator is adjusted;
Fig. 5 is a device schematic diagram of the present invention;
Fig. 6 is the schematic diagram that concerns that normallized current and demodulator are adjusted parameter;
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further details.
As shown in Figure 5, utilize the device of demodulator locks optical signal frequency to comprise with lower module in the DPSK of the present invention system: DPSK transmitting element 1, transmission link 2, DPSK receiving element 3, wherein DPSK receiving element 3 comprises that also demodulator 31, balanced reciver 32, the first current monitoring unit 33 and the second current monitoring unit 34, microprocessing unit 35, demodulator adjust circuit 36 and signal recovery unit 37.Comprise two photoelectric detector PD 1 and PD2 in the balanced reciver 32, adjust the filter wavelength of demodulator 31 and adjust parameter, the electric current of PD1, PD2 can change thereupon, and meets certain rule, when 1 road electric current of balanced reciver 32 reached maximum, another road electric current reached minimum value.The filter wavelength of demodulator can be adjusted by adjusting voltage.
It is the dpsk signal of fn that DPSK generating unit 1 produces optical signal frequency, and behind transmission link 2, light signal enters DPSK receiving element 3; After light signal enters DPSK receiving element 3, at first will import light and be divided into 2 road light signals (interfering mutually, length disappears mutually with interference), enter balanced reciver 32 then, last entering signal recovery unit 37 through demodulator 31.
The demodulator 31 of DPSK receiving element 3 needs locking optical signal frequency fn could realize optimizing reception, so the DPSK transmitting element 1 of transmitting terminal produces the bit sequence of specific pattern, behind transmission link 2, enter DPSK receiving element 3, the demodulator 31 of DPSK receiving element 3 is adjusted filter wavelength, and light signal is divided into 2 the tunnel, export to balanced reciver 32, current monitoring unit 33,34 outputs by the monitoring balanced reciver, obtain the current monitoring value and send to microprocessing unit, microprocessing unit is analyzed the current monitoring value, find out the demodulation filters wavelength of current maxima correspondence and adjust parameter, thus locking optical signal frequency fn.
The method of demodulator locks optical signal frequency of utilizing of the present invention comprises the steps:
Step 1:DPSK transmitting element 1 produces the bit sequence of specific pattern, and for example 10101010 ..., enter DPSK receiving element 3 through transmission link 2;
Step 2: DPSK receiving element 3 is adjusted the filter wavelength of demodulators 31 and is adjusted parameter, and the light signal of input is divided into 2 the tunnel enters balanced reciver 32;
Step 3: first and second current monitoring unit 33,34 detects the output current of balanced reciver 32 respectively, with the current monitoring value I that obtains
CAnd I
DSend to microprocessing unit 35;
The current monitoring unit can pass through mirror current source, through the current/voltage conversion, utilizes analog-digital converter to read the monitor value of concrete monitoring current at last again.
Step 4: 35 couples of I of microprocessing unit
CAnd I
DCarry out analyzing and processing, find current maxima, and adjust the filter wavelength adjustment parameter that circuit 36 is adjusted demodulator 31, locking optical signal frequency fn by demodulator; Specifically may further comprise the steps:
Step 41: 35 couples of I of microprocessing unit
CAnd I
DCarry out normalized
Eliminate the influence of input optical signal variable power, obtained the normallized current value;
Step 42: normalized current value is carried out match, obtain the normalization matched curve, the part of intercepting normalized curve, the principle of intercepting is that curve comprises 1 peak value and 2 valleies, and carries out match, finds out current maxima;
As shown in Figure 6, be the schematic diagram that concerns that normallized current and demodulator are adjusted parameter; Wherein, realize the expression matched curve, △ represents the normallized current monitor value, keyed end among the figure is current maxima, this current maxima is corresponding to the setting of receiver input optical signal frequency, is the desired value of the centre wavelength of filter, and expression has locked the frequency of input optical signal.
Step 43: the order demodulator is adjusted the filter wavelength adjustment parameter that circuit 36 is adjusted demodulator;
Step 44: demodulator is adjusted parameter adjustment to current maxima value corresponding, locking optical signal frequency fn with its filter wavelength.
After system operation time is long, if bigger variation takes place system frequency, need finely tune the filter wavelength of demodulator, can under the situation of interrupting service, carry out the method for locking optical signal frequency of the present invention once more; Because this moment, other parameters optimization of system were relatively stable, also can make demodulator locking optical signal frequency again by FEC error code information.
The appended embodiment of this specification is a kind of typical way that embodies the present invention's design, does not get rid of and uses other embodiment that embody design of the present invention.
Claims (6)
1. utilize the device of demodulator locks optical signal frequency in the DPSK system, comprise the DPSK transmitting element successively, transmission link, the DPSK receiving element, wherein the DPSK receiving element also comprises demodulator, balanced reciver, microprocessing unit, demodulator is adjusted circuit and signal recovery unit, demodulator is divided into 2 the tunnel with the light signal of input, this 2 road light signal all enters balanced reciver, last entering signal recovery unit, the output current of microprocessing unit analyzing and processing balanced reciver, adjust circuit by demodulator and adjust demodulation filters wavelength adjustment parameter, it is characterized in that, this device also comprises first and second current monitoring unit, described first and second current detecting unit one end links to each other with one tunnel output of balanced reciver respectively, and an end links to each other with microprocessing unit.
2. the device that utilizes the demodulator locks optical signal frequency as claimed in claim 1 is characterized in that, described first current detecting unit is a current detector.
3. the device that utilizes the demodulator locks optical signal frequency as claimed in claim 1 is characterized in that, described second current detecting unit is a current detector.
4. a method of utilizing the demodulator locks optical signal frequency is characterized in that, may further comprise the steps:
Step 1: the DPSK transmitting element produces the bit sequence of specific pattern, enters the DPSK receiving element through transmission link;
Step 2: the DPSK receiving element is adjusted the filter wavelength of demodulator and is adjusted parameter, obtains the current monitoring value, sends to microprocessing unit; Described step 2 further may further comprise the steps:
Steps A: the DPSK receiving element is adjusted the filter wavelength of demodulator and is adjusted parameter, and the light signal of input is divided into two-way, and this 2 road light signal all enters balanced reciver;
Step B: the current monitoring unit detects the output current of balanced reciver, and the current monitoring value that obtains is sent to microprocessing unit;
Step 3: microprocessing unit carries out normalized to described current monitoring value, finds current maxima, and adjusts the filter wavelength adjustment parameter that circuit is adjusted demodulator, locking optical signal frequency by demodulator.
5. the method for utilizing the demodulator locks optical signal frequency as claimed in claim 4 is characterized in that, described step 3 further may further comprise the steps:
Step a: microprocessing unit carries out normalized to the current value that receives, and obtains normalized current monitoring value;
Step b: normalized current monitoring value is carried out match, obtain matched curve, an intercepting part is wherein found out current maxima;
Step c: the order demodulator is adjusted the filter wavelength adjustment parameter that circuit is adjusted demodulator;
Steps d: demodulator is adjusted parameter adjustment to current maxima value corresponding, locking optical signal frequency with its filter wavelength.
6. the method for utilizing the demodulator locks optical signal frequency as claimed in claim 5 is characterized in that, among the described step b, the normalization matched curve of intercepting comprises 1 peak value and 2 valleies.
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| EP2621112B1 (en) * | 2012-01-24 | 2019-08-21 | Mitsubishi Electric R&D Centre Europe B.V. | Method and device for determining a presence of a locking signal in a signal received by an optical receiver device. |
| CN104125019B (en) * | 2013-04-28 | 2016-09-28 | 华为技术有限公司 | A kind of method and apparatus of Differential Quadriphase Shift Keying demodulator locks |
| CN104753842B (en) * | 2015-04-18 | 2017-10-13 | 中国电子科技集团公司第四十一研究所 | The signal modulation mode recognition methods differentiated based on peak |
| CN107631814B (en) * | 2017-09-14 | 2020-09-01 | 电子科技大学 | Optical self-coherent sensing optical path structure, frequency shift change detection method and sensing device |
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