Loss-Modulation-Based Wavelength-Range Shifting of Tunable EDF Ring Laser with Cascaded-Chirped Long-Period Fiber Grating for Temperature Measurement

A novel tunable Erbium-doped fiber ring laser (EDFRL) with a cascaded-chirped long-period fiber grating (C-CLPG) as a wavelength selection filter is proposed from the viewpoint of the sensor use, in which a variable optical attenuator (VOA) is employed as an intracavity loss modulator to change the oscillation wavelength region so that the resultant tuning wavelength range is widened. In the demonstrative experiment for temperature measurements, oscillation over the wavelength range of 12.85 nm (1557.62~1570.47 nm), which is more than three times range of the previously presented laser and is equivalent to 64 °C in terms of temperature change, was achieved, while a single-wavelength oscillation was maintained. In addition, a practical technique for realizing a temperature measurement by combining with the VOA control is also discussed.