An optical temperature sensor based on linear cavity erbium-doped fiber laser is proposed in this work. A fiber Bragg grating is utilized in the laser cavity as the sensor head for temperature detection. Experimental results suggest that the laser wavelength has linear relationship with temperature. As the temperature increases from 25 °C to 55 °C, the laser wavelength shifts linearly from 1550.168 nm to 1550.524 nm with the recorded sensitivity of 11.7 pm °C−1 . The laser is also found to be stable with fluctuation of less than 0.42 dB and it has 3 dB linewidth of 0.024 nm. Moreover, the laser has high optical signal-to-noise ratio (OSNR) of 55 dB and this arises from the use of linear cavity in this design. Resulting from the signal amplification that happens twice in the linear cavity for a round trip, the laser gets high power and this enhances the laser OSNR. The high OSNR of the laser is beneficial to improve the sensor detection limit.

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A fiber laser temperature sensor which is based on Sagnac interferometer is proposed in this work. The fiber laser consists of an erbium-doped fiber amplifier for signal amplification and a Sagnac interferometer for signal filtering. The Sagnac interferometer is made of 30 cm polarization maintaining fiber (PMF) and it acts as the sensing head. Experimental results suggest that the temperature does affect the laser wavelength. As the temperature varies from 30°C to 41°C, the laser wavelength is shifted to the lower wavelength from 1596.5 nm to 1581.8 nm with the recorded sensitivity of 1.1965 nm/°C. The change of the laser wavelength with temperature validates the use of this fiber laser as the temperature sensor.

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