CN2638081Y

CN2638081Y - Ultra narrow regulatable optical fibre laser used for concentrated wave multiplexing system

Info

Publication number: CN2638081Y
Application number: CN 03277023
Authority: CN
Inventors: 董小鹏; 陈勇
Original assignee: Xiamen University
Current assignee: Xiamen University
Priority date: 2003-07-18
Filing date: 2003-07-18
Publication date: 2004-09-01
Anticipated expiration: 2013-07-18

Abstract

The utility model relates to an ultra narrow adjustable optical fiber laser used for a concentrated wave multiplexing system. The ultra narrow adjustable optical fiber laser is provided with a pumping source, optical fiber of a mixing rare-earth element, insulators, an optical fiber coupler, and comb-shaped filter comprising high-double folding polarization-preserving fiber and a 3dB coupler. The optical fiber is connected with one end of the insulator ISO2, and the other end of the insulator ISO2 is connected with the coupler. A port of the coupler is connected with one end of another insulator ISO1, and the other end of the insulator SIO1 is connected with the comb-shaped filter which is connected with the pumping source. The port of the coupler is laser output. A reflecting port of the coupler is connected with a tunable optical fiber grating. The output power is stable, and the line width of the laser is slightly narrower and is less than 0.01 nm. The wavelength shift is less than 0.01 nm. The filter has simple design, the wavelength interval of laser can be changed by only changing the polarization-preserving fiber length of the filter to conform to the standard and suit the DWDM communication system. The omni-optical fiber design makes the insertion loss and the threshold value low, and the ultra narrow adjustable optical fiber laser is easy in use and install.

Description

The super-narrow line width adjustable optic fibre laser instrument that is used for dense wavelength division multiplexing system

(1) technical field

The utility model relates to a kind of fiber laser, in particular for the super-narrow line width adjustable optic fibre laser instrument of dense wave division multipurpose (DWDM) system.

(2) background technology

Current, the global traffic amount is the rapid growth of the Internet especially, and is more and more higher to the requirement of communication system transmits capacity.And the approach that increases the optical fiber telecommunications system transmission capacity has: the bit rate that 1) improves individual channel; 2) number of channel of increase single-core fiber; 3) increase fiber number in the optical cable.In above-mentioned these schemes, adopting the DWDM technology then is the best approach of current increase communication system transmits capacity, also is a kind of method that generally adopts at present.Because in dwdm system, interval between the different channels very little (being spaced apart 0.8nm) as the 100MHz system channel, therefore be serious inter-channel crosstalk in avoiding transmitting, the spectrum width of the needed LASER Light Source of DWDM is very narrow, and require the operation wavelength of laser instrument stable, frequency drift is little, and the laser works frequency that DWDM requires promptly requires the uniform laser instrument of frequency interval at the dwdm system frequency of operation place of International Telecommunications Union (ITU-T) suggestion.Can offer at present DWDM as light source mainly contain distributed feed-back (DFB) semiconductor laser, but these laser instruments have complex process, price height, wavelength to be difficult for shortcomings such as adjusting.

(3) summary of the invention

The utility model aims to provide a kind of simplicity of design that is used for dwdm system, output intensity is stable and output optical maser wavelength is adjustable and at setted wavelength vibration, super-narrow line width adjustable optic fibre laser instrument that live width is little.

In order to achieve the above object, the utility model utilizes rare earth doped fiber as gain media, contain Sa Kenike (Sagnac) loop of high-birefringence polarisation-maintaining optical fiber and ring cavity cooperate that linear on a large scale tunable fiber grating is realized, can swash the adjustable narrow cable and wide optical fiber laser of penetrating by the dwdm system wavelength interval output of ITU-T suggestion.

The utility model is provided with pumping source, rare earth-doped fiber, 2 fibre optic isolaters, fiber coupler, comb filter.

Pumping source excites behind the rare earth-doped fiber stimulated radiation to transmit in optical fiber loop and is exaggerated formation laser, rare earth-doped fiber connects the end of isolator ISO2, another termination fiber coupler of isolator ISO2, stimulated radiation in the rare earth doped fiber enters fiber coupler through isolator ISO2, the reflected light port of fiber coupler connects the end of another isolator ISO1, another termination comb filter of isolator ISO1, comb filter connects pumping source, fiber coupler one end is exported as laser, another termination tunable fiber grating.

Said isolator adopts the polarization irrelevant fibre optic isolater.

Said comb filter is made up of polarization maintaining optical fibre and three-dB coupler.

The utility model utilizes external agency's effect, make fiber grating Bragg wavelength that linear moving be taken place, so every cycle through a comb filter promptly just can obtain sharp penetrating that power is very strong, live width is extremely narrow when the transmission of the Bragg of fiber grating wavelength and comb filter is greatly located to coincide, and between adjacent two sharp penetrating, do not have laser to export substantially, realized that just wavelength sharply penetrates output what determine the discrete point place, the comb filter cycle of the interval of adjacent excitation wavelength and design is consistent.Select different fiber lengths just can change the cycle of comb filter according to the birefringence of polarization maintaining optical fibre, make it to meet the dwdm system wavelength interval that ITU-T advises, the fiber laser of realizing with this scheme just can be applied in the dwdm system so.This wavelength interval uniform rare earth doped fiber laser instrument, the Sagnac comb filter and the rare earth doped fiber amplifier that have adopted polarization maintaining optical fibre to constitute on the structure, linear tuning by fiber grating realized that the wavelength interval is sharp uniformly to penetrate.Compare with traditional fiber laser, its advantage is: 1) the fiber laser output power is stable; 2) laser linewidth is narrower, can be less than 0.01nm; 3) the tunable fiber grating add suitable stabilizing measures situation under, wave length shift can be less than 0.01nm, even lower; 4) comb filter simplicity of design, the length that only need change polarization maintaining optical fibre on the wave filter just can change the sharp wavelength interval of penetrating makes it to meet the ITU-T standard, to be suitable for the DWDM communication system; 5) full optical fiber designs, the insertion loss is low, and laser threshold is low, will be easier to use in system and installation.Therefore, the adjustable optic fibre laser instrument of this all optical fibre structure can be conveniently used in wavelength division multiplexer (WDM), dense wave division multiplexer fields such as (DWDM), has broad application prospects.

(4) description of drawings

Fig. 1 is a structured flowchart of the present utility model.

Fig. 2 is the output spectrum figure of the utility model embodiment.

(5) embodiment

Following examples will be further described the utility model in conjunction with the accompanying drawings.

As shown in Figure 1, pumping source (Pump) excites the excited radiation light of the certain wavelength bandwidth of rare earth-doped fiber (REDF) generation to enter fiber coupler (Fiber Coupler) through isolator ISO2.Pass through coupling mechanism, a part couples light to port one, because fiber grating is to the selection effect of wavelength, the light at the Bragg wavelength place that grating pair is answered is almost reflected back fully, light after the reflection arrives the Sagnac ring of being made up of high birefringence optical fiber and three-dB coupler (3dB Coupler) through coupling mechanism, isolator ISO1, because the polarization maintaining optical fibre birefringence is relevant with wavelength, this device that is made of high birefringence optical fiber and three-dB coupler has the comb filtering characteristic, and promptly the transmission of this wave filter and wavelength are approximate uniform period-luminosity relation.If the Bragg wavelength of grating is corresponding to the smaller part of comb filter transmission, the gain of whole loop so at this moment is less can not to form laser; When the transmission of grating Bragg wavelength and comb filter was greatly consistent, the loss minimum of whole loop, this wavelength light can produce laser when gaining enough greatly and be exported by port 2 by coupling mechanism when loop transmit.Swash and to hit the long grating Bragg consistent wavelength therewith time of cardiac wave.In sum, have only when the Bragg wavelength transmits maximal point corresponding to comb filter to form laser output, and the light of other wavelength is because the effect of comb filter can't form laser output.This shows that the output excitation wavelength is at interval by the comb filter decision, and its wavelength interval can conveniently regulate by changing comb filter, this is very simple in design.

In Fig. 1, Fiber Coupler is one common 50: 50 coupling mechanisms, ISO1, ISO2 are the polarization irrelevant isolator, ISO1 can overcome since the reflection of comb filter to the interference of signal, thereby ISO2 has avoided light through the fiber grating reflection to form the noise that vibration produces between by coupling mechanism and comb filter.High-birefringence polarisation-maintaining optical fiber (Hi-Bi Fiber) encircles with 3dBCoupler composition Sagnac and constitutes comb filter, and wherein the cycle of the length of polarization maintaining optical fibre and comb filter is inversely proportional to, the interval of the excitation wavelength of its decision fiber laser output.Pump is a powerful pumping source, and REDF is one section rare earth-doped fiber.Tunable FBG is a large-scale linear tunable fiber grating, and tuning by to fiber grating plays the excitation wavelength of selective light fibre laser, and emitting laser is by the output of OUTPUT end.

Fig. 2 is the output spectrum embodiment that adopts the narrow linewidth tunable laser of Fig. 1 scheme realization.Wherein pumping source is the 980nm long wavelength laser, and REDF is er-doped (Er) optical fiber, and horizontal ordinate is wavelength (nm), and ordinate is output intensity (dBm).As can be seen from Figure 2, the optical maser wavelength of two adjacent wavelength is equally spaced at interval substantially, and this is 0.51nm at interval by the cycle decision of comb filter.The laser extinction ratio of output is all greater than 35dB.The spectrogram that Fig. 2 provides is that the resolution of spectrometer is made as 0.01nm time scanning obtains, and at this moment resulting laser 3dB live width is extremely narrow, all less than 0.015nm.

Claims

1, the super-narrow line width adjustable optic fibre laser instrument that is used for dense wavelength division multiplexing system, it is characterized in that being provided with pumping source, rare earth-doped fiber, 2 isolators, fiber coupler and the comb filter that constitutes by high-birefringence polarisation-maintaining optical fiber and three-dB coupler, rare earth-doped fiber connects the end of isolator ISO2, another termination fiber coupler of isolator ISO2, the port of fiber coupler connects the end of another isolator ISO1, another termination comb filter of isolator ISO1, comb filter connects pumping source, the port of fiber coupler is laser output, and the reflector port of fiber coupler connects tunable fiber grating.