| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 102 === Nowadays, the bandwidth requirement for wavelength division multiplexing (WDM) system is very crucial. A tunable laser could play a role as back-up light source for individual WDM lasers, as well as a measured light source for equipments and components testing. In this thesis, C, L and C+L band tunable fiber lasers based on tunable fiber Bragg gratings (TFBGs) were investigated. It has the merits of cheaper and more flexible than most of the commercial products.
Here, two materials were utilized for realizing tunable FBGs and linear cavity fiber laser. There are hot-melt adhesive material and flexible material, respectively. The flexible material is the better one to make tunable FBG achieve a maximum tuning range of 22.4 nm with a fine-tuning resolution of 0.6 nm. The detail for parameters design and measurement are also addressed in later chapter.
Two schemes for linear cavity tunable fiber lasers are proposed in this thesis. The first scheme employs an 1×2 optical fiber coupler integrated two TFBGs, the wavelength tunable laser for C band ranges from 1534.96 nm to 1566.0 nm. The same concept can also be applied to L-band ranges from 1565.6 nm to 1599.12 nm. The second scheme employs an 1×4 optical switch (OSW) integrated four TFBGs. A segment of gain fiber is connected to the common port of the OSW. Two FBGs in port 1 and port 2, respectively, cover the C band; the other two FBGs in port 3 and port 4, respectively, cover the L band. Two segments of gain fiber are located in port 3 and port 4 to interact with the residual pump power for upgrade the lasing signal level. The whole tuning range is up to 71.58 nm (i.e., from 1528.8 nm to 1600.38 nm), covering almost the C + L band. At room temperature, the minimum and maximum output power are 3.61 dBm and 6.95 dBm, respectively, in this C+L band linear cavity fiber laser. The temperature coefficient from -10°C to 60°C has a constant value of 0.047 nm/°C for different wavelengths in-between 1534.96 nm and 1599.12 nm. At 60°C, the power variation of linear cavity fiber laser is less than ±0.07 dB before and after 12-hour burning.
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