| Optoelectronic components are the key techniques for next generation of AllOptical Net (AON). In the recent years, with the development of the techniques ofAON, its core devices have been improved, so the optical fiber communicationbecame stable and flexible increasingly. However some of the key opticalcomponents are not well developed, which limits the future improvement ofOptical Net. With the demand of big capacity and high speed of optical fibrecommunication, the dynamic tunable optical source on a certain optical frequencyband is needed. Therefore tunable broadband optical fiber laser have become theresearch focus and frontier in laser techniques. The dynamic tunable wavelength laser can provide optical source formulti-channels at the same time, which makes the design of the emission terminalmore compact and economical. It can save backup quantity and specification ofoptical source, and be easy to standardize the communication system, so therunning and maintenance cost of the systems can be reduced greatly. The tunablelaser can be used as not only optical source of DWDM system, but also PSE andLambda Router etc. It has great potential for optical communication and in thefuture the current fixed wavelength laser will be replaced by it. The tunable fiberlaser can also provide good optical source for all kinds of sensor systems andmodern spectrum techniques. Nowadays most of the lasers for communication are semiconductor lasers,which cost much and hard to couple into transfer fiber for the same size, so as tolimit further development of optical fiber communication. Semiconductor laser diode (LD) has several ways of tuning, such as electronictuning, thermal tuning and mechanical tuning etc. It can be divided into outer andinner cavity multi-electrode. However all kinds of tuning methods exist someweakness, which cannot be eliminated, such as wavelength stability reducing bythermal effect, which causes mode pulling etc. With the increasing of number ofthe channel, the semiconductor laser has to be increased. It will cost more, be hardto control wavelength and reach the requirement of the WDM wavelength standardintroduced by ITU – T. What's more it also causes problem of reliability.The optical fiber laser is better than the semiconductor laser in the followingaspects:1. The cheaper diode laser pumping the doped fiber is used, which can reduce thecost of the system;2. Fiber laser is easy to couple into transfer fiber for the same size;3. Fiber laser can be more cooler for the high area-cubage ratio;4. The wide band wavelength (380 – 3900nm) output can be obtained, which isvery important for DWDM system;5. Fiber laser and fiber amplifier is compatible with current fiber components, soit is possible to setup all optical transfer system.The gain broad band is the highlight of all advantages of the fiber laser. Due toits advantages of less coupling loss, all compatibility with optical fiber, lowpolarization relativity, high stability and low cost, the tunable Er-doped fiber laseris of significant practical value in the fields of wavelength division multiplexer(WDM) and time division multiplexer (TDM) optical fiber communication network,optical fiber sensor system and modern spectrum techniques.The ways to achieve variable wavelength output are as follows: rotatablegrating as end mirror, standard filter with adjustable angle, liquid crystal standardfilter, acousto-optic filter, F-P filter, M-Z interference filter and multiplex annularresonant cavity etc.The tunable optical fiber laser based on F-P filter is designed and developed. Ituses fiber Fabry-Perot filter as the device for wavelength tuning. The test carriedout through software simulation and optimization of related components so as toshorten the test cycle and reduce the cost. During the test it used Erbium-dopedfiber as gain medium and F-P filter as tuning component. It is ring cavity and uses1480nm laser diode as pump source. Through selecting reasonable parameter, itoptimizes the configuration of laser resonant cavity, reduces threshold value ofpump source of laser and improves slope efficiency and output power. The workingwavelength of laser is 1550nm, linewidth is less than 0.2nm in 3dB and 0.4nm in25dB, edge-mode suppression ratio is more than 50dB. After 1 hr testing, thewavelength doesn't wave, and its stability is better than 0.01nm. The laser outputduring the whole tuning process is no chirped. The continuous tuning range is1525nm – 1560.3nm (35.3nm), the spectrum band width keeps the same while thewavelength changing. The peak values of laser wavelength are flat. When thewavelength is shorter than 1530nm, ASE noise increases, however thesignal-to-noise ratio is still higher than 57dB. The reason of above is because theEr-doped laser has a higher absorption peak at the point of 1530nm. Due to theselection of erbium fiber laser of optimal length, and two isolators to reduce thenoise in the fiber loop, which increases the signal-to-noise ratio, the maximumoutput power is 80.72mW, stability of power is better than ±0.02dB and slopeefficiency of laser is 42.83%.This laser is with the advantages of high power, low threshold value, narrowline width and good stability of performance. The center wavelength can be choice,wideband tuning, high wavelength resolution, high stability, small size andreasonable performance to price ratio. |
PDF Full Text Request