CN101436906B - Apparatus and method for optimizing differential phase-shift-keyed optic transmission system - Google Patents
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Abstract
本发明提供了一种优化差分相移键控光传输系统的装置，其包括：延迟干涉仪，用于将差分相移键控信号分成两路子信号进行干涉，差分相移键控信号经延迟干涉仪干涉后解调为两路光信号，并将光信号输出到平衡接收机，差分相移键控信号中的一路的延迟时间可调；平衡接收机，用于接收来自延迟干涉仪的光信号，并对光信号进行光电转换和差分放大后将生成的电信号提供给时钟数据恢复单元；以及时钟数据恢复单元，用于接收来自平衡接收机的电信号，以对电信号进行时钟同步和数据判决来恢复原始数据。本发明还提供了一种优化差分相移键控光传输系统的方法。从而，DPSK系统的色散容限有一定程度的提高，DPSK系统更能承受窄带光合分波器滤波的影响。
The present invention provides a device for optimizing a differential phase shift keying optical transmission system, which includes: a delay interferometer, which is used to divide a differential phase shift keying signal into two sub-signals for interference, and the differential phase shift keying signal is subjected to delay interference After the interferometer is demodulated into two optical signals, and the optical signal is output to the balanced receiver, the delay time of one of the differential phase shift keying signals is adjustable; the balanced receiver is used to receive the optical signal from the delayed interferometer , and after performing photoelectric conversion and differential amplification on the optical signal, the generated electrical signal is provided to the clock data recovery unit; and the clock data recovery unit is used to receive the electrical signal from the balanced receiver, so as to synchronize the clock and data Judgment to restore the original data. The invention also provides a method for optimizing the differential phase shift keying optical transmission system. Therefore, the dispersion tolerance of the DPSK system is improved to a certain extent, and the DPSK system can better bear the influence of filtering by the narrowband optical combiner and demultiplexer.
Description
Technical field
The present invention relates to a kind of device of optimizing differential phase-shift-keyed optic transmission system.
Background technology
Along with the jumbo growth of communication service, two-forty, jumbo long Distance Transmission technology become the focus of the research of optical fiber communication in recent years.For improving the availability of frequency spectrum, reducing cost, narrow passage interval D WDM network will obtain increasing application.Differential phase keying (DPSK) (DPSK) has the raising of 3dB receiver sensitivity, superior advantages such as non-linear behaviour than non-return-to-zero (NRZ) modulation format.
In the DPSK modulation, data message is modulated on the phase difference of light carrier adjacent bit, and MZDI (Mach-ZehnderDelay Interferometer) demodulator that postpones 1 bit commonly used carries out demodulation before directly intensity detection receives.For making the light signal As soon as possible Promising Policy interference condition of two arms, need control the delay and the phase place of demodulator usually, therefore, it is as shown in Figure 1 that patent [CN1798121A] discloses the device of a kind of FEEDBACK CONTROL MZDI time of delay.It comprises interferometer structure (3), first and second arms (4,5) that this interferometer structure has the input port (1), output port (8) of the light signal that is used for receiving the DPSK modulation and extends to said output port (8) from said input port (1); The adjusting device (5,7,14,16) that is used for fine setting said two arms (4,5) delay-time difference in comprising the scope of T; Be connected to the light/electric transducer (10) of the output port (8) of interferometer structure (3); And the band pass filter (12) that is connected to the output of light/electric transducer (10), its passband does not comprise 1/T (T is a bit period).Said adjusting device (5,7,14,16) is suitable for adjusting time of delay according to the output power levels of band pass filter (12).
Above-mentioned demodulator can realize stably postponing the purpose of 1 bit time time of delay through fine setting MZDI; Solved the problem that the optical signal frequency skew brings the eye opening cost; But in dwdm system; If the bandwidth of channel join-splitting device is narrower, MZDI postpones 1 bit can introduce significant intersymbol interference, thereby make DPSK be applied in the narrow channel spacing system bigger cost is arranged.
Summary of the invention
Consider the problems referred to above and make the present invention, for this reason, main purpose of the present invention is, a kind of device of optimizing differential phase-shift-keyed optic transmission system is provided, and it comprises:
Delay interferometer is used for that the differential phase keying (DPSK) signal is divided into the two-way subsignal and interferes, and wherein the way delay of signals time is adjustable.Be demodulated into two ways of optical signals after the delayed interferometer of signal is interfered, and light signal is outputed to balanced reciver;
Balanced reciver is used to receive the light signal from delay interferometer, and light signal is carried out after opto-electronic conversion and the difference amplification signal of telecommunication that generates being offered the clock and data recovery unit; And
The clock and data recovery unit is used to receive the signal of telecommunication from balanced reciver, the signal of telecommunication is carried out clock synchronization and data decision recovers initial data;
Error code detection module is used to receive from the signal of clock and data recovery unit detecting the error rate of the signal that is received, and the error rate is outputed to feedback control unit; And
Feedback control unit is used to receive the error rate from error code detection module, and according to error rate control lag interferometer, to regulate the delay of a road in the subsignal, wherein,
Feedback control unit is used for storage and compares first state and second state; If first state is greater than second state; Then second state is saved as first state; And on second scheduled delay change direction identical, second scheduled delay of delay interferometer is changed particular value with respect to first scheduled delay, otherwise, if first state is less than second state; Then preserve first state, and on second scheduled delay change direction opposite, first scheduled delay of delay interferometer is changed particular value with respect to first scheduled delay; Wherein, With time of delay of delay interferometer being set to first scheduled delay and feedback control unit is set to initial condition; Finely tune at the first scheduled delay place so that error code detection module at the first scheduled delay place the detected error rate minimum, and with the minimum bit-error rate at the first scheduled delay place as first state; Differ second scheduled delay of particular value with first scheduled delay and finely tune changing into the time of delay of delay interferometer at the second scheduled delay place; So that error code detection module detects error rate minimum at the second scheduled delay place, and with the minimum bit-error rate at the second scheduled delay place as second state; Feedback control unit also is used to repeat to adjust second scheduled delay and obtains second state again; And second state that will obtain again and first state compare; Up to when occurring first state less than second state once more, be the optimal delay time of differential phase keying (DPSK) system the first state pairing time of delay when confirming to occur first state less than second state once more.
Delay interferometer can comprise: beam splitter is used for the differential phase keying (DPSK) signal is divided into the two-way subsignal; The adjustable delay module is used for making the road generation delay of being carried out the subsignal of beam splitting by beam splitter; And coupler, be used for interfering, and will interfere the two ways of optical signals of back generation to output to balanced reciver to the subsignal of delay with by another way signal of beam splitter output, wherein, two ways of optical signals is respectively the long mutually and signal cancellation of signal.
The adjustable delay module can be configured the time of delay that changes a road in the subsignal to different systems.
Can be arranged on time of delay greater than 0 to the scope less than 2T, wherein, T is a bit period.
Balance receiver can comprise: two optical-electrical converters, and being used in the future, the two ways of optical signals of self-dalay interferometer converts two path signal into; And differential amplifier, be used for that two path signal is carried out difference and amplify.
According to a further aspect of the invention, a kind of method of optimizing differential phase-shift-keyed optic transmission system is provided, it comprises:
Step S202; With time of delay of delay interferometer being set to first scheduled delay and feedback control unit is set to initial condition; Finely tune at the first scheduled delay place so that error code detection module at the first scheduled delay place the detected error rate minimum, and with the minimum bit-error rate at the first scheduled delay place as first state storage to feedback control unit;
Step S204; Differ second scheduled delay of particular value with first scheduled delay and finely tune changing into the time of delay of delay interferometer at the second scheduled delay place; So that error code detection module detects error rate minimum at the second scheduled delay place, and with the minimum bit-error rate at the second scheduled delay place as second state storage to feedback control unit; And
Step S206, feedback control unit compares first state and second state, and carries out handled according to comparative result;
If first state is greater than second state; Then in feedback control unit, second state is saved as first state; And on second scheduled delay change direction identical, second scheduled delay of delay interferometer is changed particular value with respect to first scheduled delay; Otherwise; If first state less than second state, is then preserved first state, and on second scheduled delay change direction opposite, first scheduled delay of delay interferometer is changed particular value with respect to first scheduled delay; And
Repeated execution of steps S204 and step S206, until occurring first state once more less than second state, be the optimal delay time of differential phase keying (DPSK) system the first state pairing time of delay when confirming to occur first state less than second state once more.
Through technique scheme, make the dispersion tolerance of DPSK system be improved to some extent, the influence of narrow band light channel join-splitting device filtering more can be born by the DPSK system.
Other features and advantages of the present invention will be set forth in specification subsequently, and, partly from specification, become obvious, perhaps understand through embodiment of the present invention.The object of the invention can be realized through the structure that in the specification of being write, claims and accompanying drawing, is particularly pointed out and obtained with other advantages.
Description of drawings
Accompanying drawing is used to provide further understanding of the present invention, and constitutes the part of specification, is used to explain the present invention with embodiments of the invention, is not construed as limiting the invention.In the accompanying drawings:
Fig. 1 shows the known sketch map that passes through the DPSK demodulating equipment of FEEDBACK CONTROL fine setting MZDI time of delay;
Fig. 2 shows the schematic representation of apparatus according to optimization differential phase-shift-keyed optic transmission system of the present invention;
Fig. 3 shows the flow chart according to the method for optimization differential phase-shift-keyed optic transmission system of the present invention;
Fig. 4 shows an embodiment according to the device of optimization differential phase-shift-keyed optic transmission system of the present invention, wherein, uses adjustable delay MZDI demodulation dpsk signal;
Fig. 5 shows the flow chart according to an embodiment of the method for optimization differential phase-shift-keyed optic transmission system of the present invention;
Fig. 6 a, Fig. 6 b, Fig. 6 c-1, Fig. 6 c-2, Fig. 6 c-3, Fig. 6 d-1, Fig. 6 d-2 and Fig. 6 d-3 show respectively system works under narrow-band optical filter adjustable delay MZDI demodulator time of delay asynchronous signal eye diagram; And
Fig. 7 shows that dispersion tolerance is with the MZDI variation of time of delay under the different optical filter bandwidth, and wherein, optical filter bandwidth is 37.5GHz and 75GHz.
Embodiment
Below in conjunction with accompanying drawing the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein only is used for explanation and explains the present invention, and be not used in qualification the present invention.
Fig. 2 shows the schematic representation of apparatus according to optimization differential phase-shift-keyed optic transmission system of the present invention.
With reference to Fig. 2, a kind of device of optimizing differential phase-shift-keyed optic transmission system is provided, it comprises:
Balanced reciver 20 is used to receive the light signal from delay interferometer 10, and light signal is carried out after opto-electronic conversion and the difference amplification signal of telecommunication that generates being offered clock and data recovery unit 30; And
Clock and data recovery unit 30 is used to receive the signal of telecommunication from balanced reciver 20, the signal of telecommunication is carried out clock synchronization and data decision recovers initial data.
Can be arranged on time of delay greater than 0 to scope less than 2T.
The device of optimizing differential phase-shift-keyed optic transmission system can also comprise: error code detection module is used to receive from the signal of clock and data recovery unit detecting the error rate of the signal that is received, and the error rate is outputed to feedback control unit; And feedback control unit, be used to receive the error rate from error code detection module, and according to the adjustable delay module of error rate control lag interferometer, to regulate the delay of a road in the subsignal.
Fig. 3 shows the flow chart according to the method for optimization differential phase-shift-keyed optic transmission system of the present invention.
With reference to Fig. 3, a kind of method of optimizing differential phase-shift-keyed optic transmission system is provided, it comprises:
Step S202; With time of delay of delay interferometer being set to first scheduled delay and feedback control unit is set to initial condition; Finely tune at the first scheduled delay place so that error code detection module at the first scheduled delay place the detected error rate minimum, and with first time of delay place minimum bit-error rate as first state storage to feedback control unit;
Step S204; Differ second scheduled delay of particular value with first scheduled delay and finely tune changing into the time of delay of delay interferometer at the second scheduled delay place; So that error code detection module locates to detect error rate minimum in second time of delay, and the minimum bit-error rate that locate second time of delay is arrived feedback control unit as second state storage; And
Step S206, feedback control unit compares first state and second state, and carries out handled according to comparative result.
The method of optimizing differential phase-shift-keyed optic transmission system can also comprise:
If first state is greater than second state; Then in feedback control unit, second state is saved as first state; And on identical change direction, second scheduled delay of delay interferometer is changed particular value, otherwise, if first state is less than second state; Then preserve first state, and on opposite change direction, first scheduled delay of delay interferometer is changed particular value; And
Repeated execution of steps S204 and step S206, until occurring first state once more less than second state, be the optimal delay time of differential phase keying (DPSK) system the first state pairing time of delay when confirming to occur first state less than second state once more.
First scheduled delay is 1.0T.
Particular value is 0.1T.
Below the preferred embodiment of present invention will be described in detail with reference to the accompanying apparatus and method.
Fig. 4 passes through illustrative and nonrestrictive example, has shown a preferred embodiment of apparatus of the present invention: realize DPSK optical transmission system optimization in Properties with FEEDBACK CONTROL adjustable delay MZDI (Mach-Zehnder DelayInterferometer) demodulator.Its device comprises: delay interferometer 10, be used for the dpsk signal of input is carried out demodulation, and wherein one tunnel delay adjustable (12), 10 two-way output are respectively the long mutually and signal cancellation of signal; Balanced reciver 20 is used for the two ways of optical signals of delay interferometer 10 outputs is carried out opto-electronic conversion and difference amplification, thus the signal of telecommunication that obtains amplifying; Clock and data recovery unit 30 is used for the signal of balanced reciver 20 outputs is carried out clock synchronization and data decision, thereby recovers initial data; Error code detection module 40 is used to monitor the error rate that receives data; Feedback control unit 50 is used to read the error rate of error code detection module 40 and regulates the time of delay of adjustable delay module 12 automatically according to error condition, makes systematic function reach best.
Three major parts that delay interferometer 10 comprises are: beam splitter (50: 50) 11 is used for being divided into two-way to the dpsk signal of input; Adjustable delay module 12 is used for one road dpsk signal is produced certain delay, and regulate its time of delay in 0.4T-1.1T (T is a bit period, down together); 2 * 2 output coupling (50: 50) 13 are used for that two-way is had the dpsk signal that postpones difference and interfere, and export the long mutually and signal cancellation light signal of signal after interfering.
Fig. 5 has shown the preferred embodiment that the inventive method realizes with installation drawing 4 through a flow chart; Its concrete operations step is following: 1. put MZDI10 and feedback control unit 50 and be initial condition; Be 1.0T the time of delay that makes MZDI; And fine setting (trimming precision 0.00001T) makes the error rate minimum, and the error rate of feedback control unit 50 stored this moments and time of delay are as state 1; 2. changing 0.1T (for example reducing 0.1T) time of delay of MZDI10, and near this time of delay, finely tune, obtain the best error rate under this time of delay, deposit this error rate and this time of delay in feedback control unit 50 as state 2; 3. the error rate to state 1 and state 2 compares in feedback control unit 50; Confirm to change the direction of time of delay with the little state of the error rate: if the error rate of state 2 is good next time; Just continue the last direction (for example continuing to reduce) that changes time of delay and change 0.1T, and save as state 1 to previous status 2; If the error code rate variance of state 2 then changes 0.1T, the attitude 1 of remaining stationary according to changing opposite direction time of delay (for example increasing) with the last time; 4. near the time of delay that step 3 obtains, finely tune, obtain the best error rate under this time of delay, this error rate and time of delay as state 2.5. repeating step 3 and 4, the direction that changes up to time of delay occurs repeatedly, then stops, and be exactly system's best configuration the 1 corresponding time of delay of state of this moment.
When system works in narrow band light channel join-splitting device following time, the dpsk signal of input is because the effect of narrow-band optical filter can produce significant intersymbol interference.If be 1 bit the time of delay of MZDI demodulator 10, significantly the signal of distortion is interfered with the opening width of balance reception back output eye pattern relatively poor.If but arrived certain optimum value the time of delay of regulating MZDI demodulator 10 less than 1 bit, the eye opening of receiver output signal could have significant improvement.The 40Gb/s wdm system is operated under the 37.5GHz optical filter bandwidth, and when be respectively 1 bit and 0.7 bit the time of delay of MZDI demodulator 10, the eye pattern of S0, S1, S2, S3 signal was as shown in Figure 6 among Fig. 4.Wherein, Fig. 6 a shows the dpsk signal of transmitter output, and Fig. 6 b shows the S0 signal of input MZDI behind the 37.5GHz optical filter; Fig. 6 c-1 shows the S1 signal that MZDI postpones 1 bit; Fig. 6 c-2 shows the S2 signal that MZDI postpones 1 bit, and Fig. 6 c-3 shows the S3 signal that MZDI postpones 1 bit, and Fig. 6 d-1 shows the S1 signal that MZDI postpones 0.7 bit; Fig. 6 d-2 shows the S2 signal that MZDI postpones 0.7 bit, and Fig. 6 d-3 shows the S3 signal that MZDI postpones 0.7 bit.S0 is the signal that gets into MZDI demodulator 10, and the dpsk signal that the contrast transmitter sends can be clear that very big distortion has taken place the S0 of process narrow-band filtering; S3 is the signal of balanced reciver 20 outputs, and the eye pattern of S3 can be known when contrast postponed 1 bit and 0.7 bit, and the eye opening when postponing 0.7 bit is significantly improved than the eye opening that postpones 1 bit.Fig. 7 be under the different optical filter bandwidth (37.5GHz and 75GHz) dispersion tolerance with the MZDI variation of time of delay.As can be seen from the figure, along with reducing of MZDI time of delay, dispersion tolerance all is improved to some extent under these two kinds of optical filter bandwidth.
Though show and the application of institute of the present invention extracting method and the realization of device be described with reference to the preferred embodiments of the present invention; But it should be appreciated by those skilled in the art; The realization of delay interferometer 10 is not limited to the MZDI among the embodiment; Can also be Michelson steller interferometer etc., come the demodulation dpsk signal through delayed interference as long as satisfy; The realization of adjustable delay also is not limited to pure optical fiber, planar lightwave circuit, waveguide or the free space light path etc. used always; The control of regulating both can be manual, also can realize with feedback control unit; The monitoring variable of FEEDBACK CONTROL both can be the error rate, also can be output voltage of balanced reciver etc., and the design of FEEDBACK CONTROL and operating procedure also are diversified.
The above is merely the preferred embodiments of the present invention, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.All within spirit of the present invention and principle, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
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