A fabrication method of the multi-wavelength fiber grating (FBG) was introduced. Using\nthe scan exposure method, the multi-wavelength FBG can be successfully manufactured through\napplying different tensile forces during the multiple exposures process on the same fiber. Experiment\nresults show that the position and the overlap of different sub FBGs will greatly affect the spectrum\nof every sub FBG. The spectrum of each sub FBG will be affected by short wave oscillation unless\nthe lengths and positions of all sub FBGs are fully overlapped. For hydrogen loaded fiber, the\nwavelength and reflectivity of the nth level FBG will increase as the (n+1)th level FBG is written.\nBut for germanium doped photosensitive fiber, multiple exposure will increase the wavelength of\nprevious sub FBGs while decrease the reflectivity of all sub FBGs. Through well distributing\nexposure intensity of every sub FBGs, a four-wavelength FBG with same sub FBG�s spectrum was\nfabricated on a hydrogen loaded single mode fiber.
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