CN103576222A - CS-RZ to RZ code type conversion fiber bragg grating designing method and device thereof - Google Patents

Abstract

The invention discloses a CS-RZ to RZ code type conversion fiber bragg grating designing method and a device thereof. The method comprises the steps of giving a group of pseudo-random codes, acquiring a discretization number value sequence of CS-RZ codes and a discretization number sequence of NRZ codes according to the given duty ratio and the signal rate, carrying out fast fourier transform on the two discretization number value sequences to obtain discretization number value sequences to two power spectrums, blue shifting or red shifting the central wavelength of a discretization number value sequence of a power spectrum of a CS-RZ signal at the wavelength width corresponding to the bit rate of a half CS-RZ signal to obtain a CS-RZ signal spectrum, using a discretization number value sequence of an NRZ power spectrum to subtract the CS-RZ signal spectrum to obtain a new discretization number value sequence, choosing a cutting window with the cutting width corresponding to the wavelength widths of the bit rates of two CS-RZ signals to cut the new discretization number value sequence to obtain a complete characteristic spectrum of a fiber bragg grating and utilizing a reversed layer peeling method to obtain a grating structure. The device is good in filtering effect, can effectively restrain code pattern effect and ripple wave pulsation and can acquire higher Q values.

Description

CS-RZ is to NRZ pattern conversion fiber grating method for designing and device thereof

Technical field

The present invention relates to technical field of optical network communication, in particular a kind of full optical code type conversion apparatus from Carrier-Suppressed Return-to-Zero (CS-RZ) to nonreturn to zero code (NRZ).

Background technology

Following high-speed high capacity optical communication system will merge dense wave division multipurpose (DWDM) and Optical Time Division Multiplexing (OTDM) technology on the one hand to improve transmission capacity and speed.On the other hand, in order further to improve transmission capacity, the raising band efficiency (spectral efficiency is called for short SE) of optical communication system, many modulation formats novel, that have high spectrum efficiency, unique transport property will be used.New modulation techniques becomes one of gordian technique in High Speed System.Along with people are to modulating going deep into of technical research, except making zero (RZ) code and these traditional modulation formats of non-return-to-zero (NRZ) code, various new modulation formats continue to bring out, and Carrier-Suppressed Return-to-Zero (CS-RZ) is exactly one of them.This modulation format is proposed in 1999 first by MIYAMOTO, belongs to pseudo-multi-level modulation form.This modulation format itself is both with amplitude modulation information, also with phase information, the OOK(alternating-phase OOK that a kind of phase place changes) modulation format, from the angle of dispersion tolerance, SPM tolerance limit, nonlinear impairments tolerance limit, come, CS-RZ code is a kind of good modulation format.

The spectrum of CS-RZ is narrow, is approximately half of RZ code, so spectrum efficiency is high compared with RZ code; In addition, it is warbled and is mainly present in the place that two pulses are joined, therefore higher to the tolerance of dispersion.There are some researches show, CS-RZ code is obviously better than NRZ code in the impact of alleviating nonlinear effect, and it not only allows higher launched power, and Power penalty is also significantly less than NRZ code, is suitable for backbone network.

Nonreturn to zero code (NRZ) has that production method is simple, frequency band is narrow, have channel wavelength spacing closely, and the higher advantages such as spectrum efficiency, are suitable for being applied in dense wave division multipurpose (DWDM) technology that spectrum efficiency is had relatively high expectations; In addition, NRZ pattern also has the friendly to electronics device, and therefore stronger time jitter tolerance and dispersion tolerance but non-linear tolerance is low, transmission range is near be generally suitable for Metropolitan Area Network (MAN) and Access Network.

Different OOK patterns, because thering is different time domains, frequency domain characteristic is suitable for different networks, so interface in commercial high speed OTDM and DWDM network system, between various OOK patterns, mutually the pattern switch technology, particularly full optical code type switch technology of conversion become one of important, requisite network interface techniques.

At present, the pattern conversion about NRZ to CS-RZ, Wandi Li, Jian Wang etc. has reported two kinds of technical schemes:

1. utilize semiconductor optical amplifier to form the active pattern switch technology (W.D.Li of fiber loop mirror, M.H.Chen, Y.Dong, and S.Z.Xie, " All-optical format conversion from NRZ to CSRZ and between RZ and CSRZ using SOA-based fiber loop mirror; " IEEE Photon.Technol.Lett.16,203-205 (2004) .);

2. utilize the nontransparent characteristic of period polarized reversion lithium niobate (PPLN) optical waveguide to realize active pattern switch technology (the Jian Wang of NRZ-to-CSRZ, Junqiang Sun, Xinliang Zhang, and Dexiu Huang, / Proposal for PPLN-Based all-optical NRZ-to-CSRZ, RZ-to-CSRZ, RZ-DPSK-to-CSRZ-DPSK, and RZ-DPSK-to-CSRZ-DPSK format conversions, 0IEEE Photonics Technol.Lett.20,1039-1041 (2008), and the full optical code type conversion to NRZ about CS-RZ, only the people such as Yu Yu has reported that a kind of Mach-Zehnder that utilizes interferes (optical-fiber time-delay interferometer at present, DI) passive pattern switch technology scheme (the Yu Yu of cascade narrow band filter, Xinliang Zhang, and Dexiu Huang, ' All-Optical Format Conversion from Cs-Rz to Nrz at40gbit/S', Optics express, 15 (2007), 5693-98, Yu Yu, Xinliang Zhang, and Dexiu Huang, ' Simultaneous All-Optical Multi-Channel Rz and Csrz to Nrz Format Conversion', Optics Communications, 284 (2011), 129-35).This scheme can be worked in passive mode, although relatively active pattern switching device has simple in structurely, cost performance is high, steady performance.Its shortcoming is: 1. owing to having adopted the structure of the interferometers such as DI, adjustment operation is more difficult, and cost is higher; 2. adopt the scheme of interferometer cascade wave filter, be actually with two wave filters frequency spectrum is carried out to the function that secondary cutting realizes pattern conversion, the technology of only carrying out a cutting straight forming with a wave filter is not provided, cause prior art relative complex, cost improves relatively, is unfavorable for using in batches in commercial system; 3. filter effect is not good enough, and pattern effect is obvious.The symmetric form spectral response that two filter banks obtain be not CS-RZ to the optimal spectrum response of NRZ pattern conversion, optimal spectrum response should be carried out specific design according to the two frequency spectrum difference of CS-RZ, NRZ and obtain.

Summary of the invention

Object of the present invention, overcome exactly the deficiencies in the prior art, provide a kind of passive CS-RZ based on cutter type spectral response fiber grating to NRZ full optical code type conversion special purpose device and method for designing thereof, this is different from the existing device that carries out secondary spectrum cutting based on interferometer cascade narrow band filter, the fiber grating filter that only need be designed by method for designing of the present invention, without additional any other active or passive device.

In order to achieve the above object, adopt following technical scheme:

To a NRZ pattern conversion fiber grating method for designing, bag following steps:

A given group code stream length is 2 ⁿ-1 pseudo-random code, the discretize sequence of values of CS-RZ code and NRZ code when providing dutycycle and be certain value, signal rate and being definite value;

Two groups of discretize sequence of values are done to fast fourier transform, take decibel as unit, obtain the discretize sequence of values of the two power spectrum;

By the wavelength width corresponding to bit rate of the centre wavelength blue shift of the discretize sequence of values of the power spectrum of CS-RZ signal or half CS-RZ signal of red shift, obtain the CS-RZ signal spectrum after centre wavelength blue shift or red shift;

With the CS-RZ signal spectrum that the discretize sequence of values of NRZ power spectrum deducts after blue shift or red shift, obtain one group of new discretize sequence of values;

Choose cutting width and be the crop window of the wavelength width that the bit rate of two CS-RZ signals is corresponding new discretize sequence of values is carried out to cutting, obtain the characteristic spectrum that fiber grating is complete;

According to the characteristic spectrum of fiber grating, adopt and comprise that discrete reverse layer strip obtains the structure of grating.

The CS-RZ obtaining according to above-mentioned method for designing design transforms fiber grating device to NRZ pattern, for the CS-RZ signal to be converted of setting signal speed being converted to the NRZ signal of same signal rate, comprise the fiber grating with cutter type spectral response, it consists of fiber grating main body and grating the first port and two ports of grating the second port.

Further, also comprise a circulator, described circulator is connected with fiber grating, and RZ signal to be converted enters from circulator, then is back to circulator after entering into fiber grating, and exports from circulator.

Further, described signal rate is more than or equal to 10Gbit/s, and is less than or equal to 200Gbit/s.

Compared with prior art, beneficial effect of the present invention is:

1. the conversion device structure being obtained by method for designing of the present invention design is simple, uses easy to operate: whole conversion equipment is reduced to a fiber grating with cutter type spectral response, is that a kind of CS-RZ of simplifying is most to NRZ full optical code type conversion apparatus.

2. good wave filtering effect, can effectively suppress pattern effect and ripple pulsation, obtains higher Q value simultaneously.

3. pair WDM signal is transparent.The CS-RZ signal of WDM, directly carries out by the present invention the NRZ signal or the WDM signal that after pattern conversion, obtain, and the process of not additional demultiplexing does not need to add the wavelength division multiplexers such as AWG yet and carries out multiplexingly just can directly in wdm system, transmitting.

4. possesses multichannel translation function simultaneously: construct a multichannel optical fiber grating and can realize multi channel CS-RZ to the conversion of NRZ pattern simultaneously, for example, emulation experiment adopts 4 channels.

5. the passive working method of full raster, energy-conserving and environment-protective, stable performance, without additional noise, with existing optical fiber telecommunications system highly compatible.

Accompanying drawing explanation

Fig. 1 is ultimate principle figure of the present invention;

Fig. 2 is the power spectrum of CS-RZ signal;

Fig. 3 is that CS-RZ power spectrum signal is through the figure of fiber grating spectrum cutting;

Fig. 4 is the power spectrum of NRZ;

Fig. 5 is CS-RZ, NRZ pattern power spectrum comparison diagram;

Fig. 6 is fiber grating characteristic spectrum cutting schematic diagram and filtering order optimization figure.

Fig. 7 is that conversion gained NRZ pattern Q value is with the change curve of filtering order;

Fig. 8 is that the standard deviation of 1 yard of conversion gained NRZ pattern is with the change curve of filtering order;

Fig. 9 is index modulation function and the local chirp value of fiber grating; .

Figure 10 is the comparison diagram of object penetrating spectrum and simulated transmission spectrum;

Figure 11 is the oscillogram of the CS-RZ signal of 20Gbit/s;

Figure 12 is the transmission spectrum of fiber grating of the CS-RZ signal input of 20Gbit/s;

After Figure 13 is the CS-RZ signal input of 20Gbit/s, the oscillogram of the NRZ of output;

After Figure 14 is the CS-RZ signal input of 20Gbit/s, the eye pattern of NRZ after conversion;

Figure 15 be in embodiment bis-the full light CS-RZ of 40Gbit/s to NRZ code type conversion apparatus schematic diagram;

Figure 16 is the eye pattern of the NRZ pattern signal after the full light CS-RZ conversion of 40Gbit/s;

Figure 17 is the reflectance spectrum of 4 channel fiber gratings;

Figure 18 is that the full light CS-RZ of 4 channel 40Gbit/s is to index modulation function and the local chirp value of NRZ pattern conversion fiber grating.

Embodiment

Below in conjunction with accompanying drawing and specific implementation method, describe the present invention in detail, in exemplary embodiment and description of the present invention, be used for explaining the present invention, but not as a limitation of the invention.

As shown in Figure 1, passive CS-RZ based on cutter type spectral response fiber grating of the present invention is used for the CS-RZ signal to be converted of setting signal speed to convert to NRZ full optical code type conversion apparatus the NRZ signal of same signal rate, comprise the fiber grating with cutter type spectral response, it consists of fiber grating main body 2 and grating the first port one and 3 two ports of grating the second port.The spectral response of described fiber grating main body, be that transmission spectrum or reflectance spectrum are according to the spectral composition feature of the NRZ signal of the spectral composition of the CS-RZ signal to be converted of special speed and corresponding bits speed, wavelength centered by one of two sidebands of selection CS-RZ frequency spectrum, be relative carrier frequency red shift or frequency corresponding to blue shift 1/2nd bit rates, calculate the poor of NRZ power spectrum and CS-RZ power spectrum, asymmetric line according to the difference of power spectrum about centre wavelength, takes different disposal method to design respectively in the centre wavelength left and right sides to obtain.The special speed here refers to that speed is more than or equal to 10Gbit/s, and is less than or equal to the CS-RZ signal of 200Gbit/s.The Refractive index modulation distribution of fiber grating main body and the distribution of warbling are to be obtained by spectral response inverting according to cause-effect relationship, and fiber grating can adopt publicly-owned method to inscribe and make.

As shown in Figure 1, CS-RZ signal to be converted enters grating the first port one, by fiber grating main body 2, from the angle analysis of frequency domain, fiber grating main body 2 is just equivalent to a wave filter, its cutter type spectral response, be that transmission spectrum or reflectance spectrum will carry out cutting to the frequency spectrum of the CS-RZ signal to be converted of described special speed, cutting center is certain sideband of selected CS-RZ frequency spectrum, and the left and right sides obtains different cutting amounts, and cutting amount size is determined by the spectral response of cutter type.A cutting by the spectral response of cutter type completes Spectrum Conversion, realizes the adjustment of pulse shape in time domain, completes pattern conversion, obtains NRZ signal.If the transmission spectrum that the spectral response of described cutter type is fiber grating, transmitted light has comprised the NRZ signal that pattern is converted to, and described NRZ signal is from grating the second port 3 outputs.Otherwise if described cutter type frequency spectrum should be the reflectance spectrum of fiber grating, reflected light has comprised the NRZ signal that pattern is converted to, described NRZ signal is from the first port one output of institute's grating.As shown in Figure 2, it is that CS-RZ signal is from the power spectrum of the CS-RZ signal of grating the first port one input.As shown in Figure 3, the situation of optical fiber grating spectrum cutting during CS-RZ signal process fiber grating main body 2, black dotted lines represents the characteristic spectrum of fiber grating.As shown in Figure 4, it is the power spectrum from the NRZ of grating second port 3 output of fiber grating.

The cutter type transmission spectrum of fiber grating or reflectance spectrum are to design according to the spectral composition of the NRZ signal of the spectral composition of special speed CS-RZ signal to be converted, centre wavelength red shift or blue shift and corresponding bits speed.The spectrum of CS-RZ signal to be converted of input, suppressed because of carrier wave, at carrier wave place, there is no obvious line spectrum, but carrier wave each side there is a very strong line spectrum, be called the sideband of CS-RZ code, the difference on the frequency between two sidebands equals bit rate.The spectrum of NRZ code comprises continuous spectrum part and in the very strong discrete line spectrum at carrier wave place, at the frequency place of bit rate integral multiple, remaining line spectrum is compared with the line spectrum at carrier wave place, much weak.The difference of the spectral composition maximum of CS-RZ and NRZ signal has the spectrum carrier wave of two point: 1.CS-RZ suppressed, there are two very strong sidebands, i.e. two very strong discrete line spectrums, and only at carrier wave place, there is a very strong discrete line spectrum in NRZ spectrum, single order sideband is very weak, negligible.2. after centre wavelength red shift or blue shift, the spectrum of CS-RZ loses symmetrical property, and the spectrum of NRZ is symmetrical.

Fiber grating of the present invention, as a bandpass filter, designs for two large differences of the two spectrum, and a sideband in CS-RZ frequency spectrum is retained, and another one sideband filters out.To select centered by the sideband of reservation, CS-RZ frequency spectrum after centre wavelength red shift or blue shift and the NRZ frequency spectrum centered by carrier wavelength are compared, obtain the centre wavelength left and right sides different filter curve separately, thereby obtain the cutter type spectral response curve of fiber grating.Optimal design shows, the pattern conversion effect optimum that first-order filtering obtains.

The structural parameters of fiber grating of the present invention, Refractive index modulation distribution and the distribution of warbling are to obtain by spectral response inverting according to the cause-effect relationship between optical grating construction and spectral response.Spectral response is the concrete manifestation of fiber grating filtering characteristic, and its essence is by the unique decision of optical fiber grating structure, the two Satisfying Causality relation.Therefore, determine required spectral response, according to known algorithm, just can calculate the whole structural parameters of grating according to spectral response.According to Refractive index modulation distribution and the distribution of warbling, just can adopt publicly-owned method, for example point-to-point writing method is inscribed and is made, thereby obtains fiber grating of the present invention.

Provide the design process of fiber grating spectral response below:

Embodiment mono-:

The full light CS-RZ of a kind of single channel 20Gbit/s of take is below example to NRZ pattern conversion designs method.

The first step: a given group code stream length is 2 ⁿ-1 pseudo-random code, when providing 67% dutycycle, signal rate and be 20Gbit/s according to publicly-owned method, the discretize numeral of CS-RZ code and NRZ code is described, i.e. discretize sequence of values S _cS-RZand S (t) _nRZ(t).

Second step: to S _cS-RZand S (t) _nRZ(t) these two groups of discretize sequence of values are done fast fourier transform, take decibel as unit, obtain the discretize sequence of values SPCT of the two power spectrum _{org_CS-RZ}(Δ λ) and SPCT _nRZ(Δ λ).As shown in Figure 5, solid line represents SPCT _nRZ(Δ λ), dotted line represents SPCT _{org_CS-RZ}(Δ λ)), that is:

S_FFT _CS-RZ=FFT(S _CS-RZ(t))

S_FFT _NRZ=FFT(S _NRZ(t))

SPCT _{org_CS-RZ}(Δλ)=10*log(S_FFT _CS-RZ×S_FFT _CS-RZ ^*/T)

SPCT _NRZ(Δλ)=10*log(S_FFT _NRZ×S_FFT _NRZ ^*/T)

S_FFT wherein _cS-RZ ^*for S_FFT _cS-RZcomplex conjugate, S_FFT _nRZ ^*for S_FFT _nRZcomplex conjugate, T is the time to chopping determined by code stream length, Δ λ=λ-λ _c, λ _ccentered by wavelength be carrier wavelength.

The 3rd step: by the SPCT of CS-RZ signal _{org_CS-RZ}(Δ λ) centre wavelength blue shift or red shift

obtain CS-RZ signal spectrum SPCT after centre wavelength blue shift or red shift _cS-RZ(Δ λ).B wherein _1rdcorresponding wavelength width while being converted into YinmWei unit for signal bit rate, i.e. bandwidth between two sidebands of CS-RZ frequency spectrum, when signal bit rate is 20Gbit/s, B _1rd=0.16nm.Even:

${\mathrm{SPCT}}_{\mathrm{CS}-\mathrm{RZ}}\left(\mathrm{\&Delta;\&lambda;}\right)={\mathrm{SPCT}}_{\mathrm{org}\_\mathrm{CS}-\mathrm{RZ}}(\mathrm{\&Delta;\&lambda;}\&PlusMinus;\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000405730720000031.png,HDA0000405730720000032.png"\; state="\{\{state\}\}">B</figure-callout>}}_{1\mathrm{rd}})$

Wherein, positive sign and negative sign corresponding blue shift and red shift respectively.In Fig. 6, solid line provides the situation of centre wavelength blue shift, below take blue shift and designs as example, for the situation of red shift, with reference to the flow process of blue shift, processes, and does not repeat them here.

The 4th step: with the discretize sequence of values SPCT of NRZ power spectrum _nRZ(Δ λ) deducts CS-RZ blue shift

the discretize sequence of values SPCT of power spectrum _cS-RZ(Δ λ), obtains one group of new discretize sequence of values SPCT _nRZ-CS-RZ(Δ λ), as shown in phantom in Figure 6.The centre wavelength left and right sides of Fig. 6 is asymmetric, SPCT _grtand SPCT _grtaccording to asymmetrical SPCT _nRZ-CS-RZthe left and right sides is designed respectively, whole formation cutter type spectral response.

That is:

SPCT _NRZ-CS-RZ(Δλ)=SPCT _NRZ(Δλ)-SPCT _CS-RZ(Δλ)

The 5th step: according to the difference SPCT of power spectrum _nRZ-CS-RZ(Δ λ) near centre wavelength ± B _1rdvalue condition in (± 0.16nm) scope, minute left and right two parts are processed.Left-half SPCT _nRZ-CS-RZbe greater than zero, as wave filter, because not possessing the function of power amplification, its transmitance or reflectivity all can not surpass 0dB, therefore the left-half of fiber grating characteristic spectrum is designed to approach a value of 0dB; Right half part SPCT _nRZ-CS-RZbe less than zero, can be directly as the part of fiber grating characteristic spectrum.Choosing like this cutting width is ± B _1rdcrop window to SPCT _nRZ-CS-RZcarry out cutting, obtain the characteristic spectrum SPCT that fiber grating is complete _grt, for 20Gbit/s CS-RZ code, B _1rd=0.16nm, obtains characteristic spectrum SPCT _grtas shown in solid line in Fig. 6:

$\left\{\begin{array}{cc}{\mathrm{SPCT}}_{\mathrm{grt}}\left(\mathrm{\&Delta;\&lambda;}\right)={\mathrm{SPCT}}_{\mathrm{NRZ}-\mathrm{CS}-\mathrm{RZ}}\left(\mathrm{\&Delta;\&lambda;}\right)& 0\&le;\mathrm{\&Delta;\&lambda;}\&le;{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000405730720000031.png,HDA0000405730720000032.png"\; state="\{\{state\}\}">B</figure-callout>}}_{1\mathrm{rd}}\\ {\mathrm{SPCT}}_{\mathrm{grt}}\left(\mathrm{\&Delta;\&lambda;}\right)=-0.01\mathrm{dB}& -{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000405730720000031.png,HDA0000405730720000032.png"\; state="\{\{state\}\}">B</figure-callout>}}_{1\mathrm{rd}}\&le;\mathrm{\&Delta;\&lambda;}<0\\ {\mathrm{SPCT}}_{\mathrm{grt}}\left(\mathrm{\&Delta;\&lambda;}\right)=-40\mathrm{dB}& \mathrm{\&Delta;\&lambda;}\&le;-{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000405730720000031.png,HDA0000405730720000032.png"\; state="\{\{state\}\}">B</figure-callout>}}_{1\mathrm{rd}}\\ {\mathrm{SPCT}}_{\mathrm{grt}}\left(\mathrm{\&Delta;\&lambda;}\right)=-40\mathrm{dB}& \mathrm{\&Delta;\&lambda;}\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000405730720000031.png,HDA0000405730720000032.png"\; state="\{\{state\}\}">B</figure-callout>}}_{1\mathrm{rd}}\end{array}\right.$

That is: in cutting window, 0≤Δ λ≤B _1rdregion, make SPCT _grt(Δ λ)=SPCT _nRZ-CS-RZ(Δ λ) ,-B _1rdin the region of≤Δ λ <0, the left-half of characteristic spectrum is designed to approach a value of 0dB, makes SPCT _grt(Δ λ)=-0.01dB; In cutting, make SPCT outside window _grt(Δ λ) is an approaching small value (40dB) of zero, but can not get zero, so that the design of next step grating and physics realization.In crop window, obtain so a kind of cutter type spectral response, by optimization, calculate and show, the fiber grating that utilization has a this cutter type spectral response carries out first-order filtering and just can obtain best filter effect, and this has been that CS-RZ changes best spectral response to NRZ pattern.

Fig. 7 and Fig. 8 are respectively the standard deviation of conversion gained NRZ pattern Q value and 1 yard with the change curve of filtering order, in figure, curve illustrates that respectively first-order filtering can obtain maximum Q value and 1 yard of minimum standard deviation, adopt first-order filtering, when obtaining maximum Q value, can well suppress pattern effect.

As everyone knows, if need the NRZ signal obtaining after conversion from grating the first port output, make the reflectance spectrum r of fiber grating ²(Δ λ) equals characteristic spectrum SPCT _grt(Δ λ), otherwise, if need the NRZ signal obtaining after conversion to export from the second port of fiber grating, make the transmission spectrum t of fiber grating ²(Δ λ) equals characteristic spectrum SPCT _grt(Δ λ), even:

10*log (r ²(Δ λ))=SPCT _grt(Δ λ) the first port of grating is output terminal

Or 10*log (t ²(Δ λ))=SPCT _grt(Δ λ) the second port of grating is output terminal

T wherein ²(Δ λ)+r ²(Δ λ)=1.

The 6th step: according to the characteristic spectrum SPCT of fiber grating _grt(Δ λ), employing such as discrete reverse layer strip etc. designed the structure of grating.Refractive index modulation distribution as shown in Figure 9 and the distribution of warbling, complete grating design process.As shown in Figure 10,

The CS-RZ signal to be converted of 20Gbit/s code type conversion apparatus of the present invention enters grating the first port one, see through fiber grating main body 2, the frequency spectrum of CS-RZ signal to be converted is subject to the cutting of fiber grating transmission spectrum, by a cutting, complete Spectrum Conversion, realize pulse strenching, complete pattern conversion, obtain the NRZ signal of 20Gbit/s and from grating the second port 3, export the relative CS-RZ of NRZ signal signal center wavelength blue shift

b wherein _1rdcorresponding wavelength width while being converted into YinmWei unit for signal bit rate, i.e. bandwidth between two sidebands of CS-RZ frequency spectrum, when signal bit rate is 20Gbit/s, B _1rd=0.16nm.Figure 11 is the waveform of the CS-RZ pattern signal of input, the transmission spectrum that Figure 12 is fiber grating, and Figure 13 is the waveform of the NRZ pattern signal of output, Figure 14 is the eye pattern of NRZ pattern signal.The transmission spectrum of this fiber grating designs according to the two difference of 20Gbit/s CS-RZ signal spectrum and 20Gbit/s NRZ signal spectrum, according to the requirement of eliminating 20Gbit/s CS-RZ flashlight spectrum distance carrier wave+0.16nm place sideband, its bandwidth Design is 0.32nm, ± 0.16nm place provides the filter effect that is greater than 40dB, reaches the object of pattern conversion.After conversion, as shown in figure 14, eye pattern opens greatly the eye pattern of NRZ pattern signal, and Q value is 64.39.

Embodiment bis-

The full light CS-RZ of a kind of multichannel 40Gbit/s of take is below example to NRZ pattern conversion designs method.As shown in figure 15, circulator 4 comprises A, B, tri-ports of C to its device, and fiber grating comprises grating the first port one and 2 two ports of grating the second port.WDM CS-RZ signal to be converted is from the A port input of circulator 4, from circulator C port, export, enter grating the first port one, after the reflection of fiber grating main body, from grating the first port one, export, from circulator C port, enter circulator, and from the output of circulator B port, obtain 40Gbit/s WDM NRZ signal.Figure 16 is the eye pattern of the rear NRZ pattern signal of conversion, and Figure 17 is the reflectance spectrum of 4 channel fiber gratings.Because the signal after pattern conversion is from grating the first port one output, so the reflectance spectrum that the characteristic spectrum is here fiber grating.The characteristic spectrum of this fiber grating (reflectance spectrum) designs according to the two difference left and right two parts of the wavelength blue shift 0.16nm of 40Gbit/s CS-RZ signal center gained spectrum and 40Gbit/s NRZ signal spectrum, according to the requirement of eliminating 40Gbit/s CS-RZ flashlight spectrum distance carrier wave+0.32nm place sideband, each channel width is designed to 0.60nm, at ± 0.32nm place, provide the filter effect that is greater than 40dB, channel spacing is taken as the corresponding 200GHz of 1.6nm() to eliminate crosstalking of interchannel, reach the object of pattern conversion.After conversion, as shown in figure 16, eye pattern opens greatly the eye pattern of NRZ pattern signal, calculates and obtains, and Q value is 53.68.

Wherein the design of 4 channel fiber gratings need be only 4 by the number of channel, each channel width is got 0.60nm, dutycycle gets 50%, channel spacing is got the corresponding 200GHz of 1.6nm(), according to the fiber grating design procedure providing in above-described embodiment 1, multichannel optical fiber grating design method with reference to publicly-owned, does not repeat them here.Figure 18 provides 4 channels, and the full light CS-RZ of 40Gbit/s of channel spacing 200GHz is to the optical grating construction of NRZ pattern conversion fiber grating, and it comprises index modulation function and local chirp value.

The technical scheme above embodiment of the present invention being provided is described in detail, applied specific case herein the principle of the embodiment of the present invention and embodiment are set forth, the explanation of above embodiment is only applicable to help to understand the principle of the embodiment of the present invention; , for one of ordinary skill in the art, according to the embodiment of the present invention, in embodiment and range of application, all will change, in sum, this description should not be construed as limitation of the present invention meanwhile.

Claims (4)

1. CS-RZ, to a NRZ pattern conversion fiber grating method for designing, is characterized in that, comprises the following steps:

A given group code stream length is 2 ⁿ-1 pseudo-random code, the discretize sequence of values of CS-RZ code and NRZ code when providing dutycycle and be certain value, signal rate and being definite value;

Two groups of discretize sequence of values are done to fast fourier transform, take decibel as unit, obtain the discretize sequence of values of the two power spectrum;

By the wavelength width corresponding to bit rate of the centre wavelength blue shift of the discretize sequence of values of the power spectrum of CS-RZ signal or half CS-RZ signal of red shift, obtain the CS-RZ signal spectrum after centre wavelength blue shift or red shift;

With the CS-RZ signal spectrum that the discretize sequence of values of NRZ power spectrum deducts after blue shift or red shift, obtain one group of new discretize sequence of values;

Choose cutting width and be the crop window of the wavelength width that the bit rate of two CS-RZ signals is corresponding new discretize sequence of values is carried out to cutting, obtain the characteristic spectrum that fiber grating is complete;

According to the characteristic spectrum of fiber grating, adopt and comprise that discrete reverse layer strip obtains the structure of grating.

2. the CS-RZ that method for designing design according to claim 1 obtains transforms fiber grating device to NRZ pattern, for the CS-RZ signal to be converted of setting signal speed being converted to the NRZ signal of same signal rate, it is characterized in that: comprise the fiber grating with cutter type spectral response, it consists of fiber grating main body and grating the first port and two ports of grating the second port.

3. CS-RZ according to claim 2 transforms fiber grating device to NRZ pattern, it is characterized in that: also comprise a circulator, described circulator is connected with fiber grating, RZ signal to be converted enters from circulator, after entering into again fiber grating, be back to circulator, and export from circulator.

4. CS-RZ according to claim 1 and 2 transforms fiber grating device to NRZ pattern, it is characterized in that: described signal rate is more than or equal to 10Gbit/s, and is less than or equal to 200Gbit/s.

Images