Fiber Bragg grating sensing system using a TO-can-based compact optical module for wavelength demodulation

A combined scheme using the light source of a reflective semiconductor optical amplifier (RSOA) and an optical signal processing unit (OSPU) based on the compact TO-can package is fabricated and characterized for a fiber Bragg grating (FBG) sensing system. Due to the optical feedback behavior from the FBG sensor, the RSOA is self-injection locked and lasing occurs at the Bragg wavelength. Using the wavelength-dependent filter method, all of the components in the OSPU are compactly integrated on the TO-can package with a height of 17.6 mm and diameter of 6.0 mm. The wavelength demodulating output signals are based on the optical power difference, depending only on the wavelengths without the effect of input optical power variations. The sensitivity of the output signal to temperature shows 0.026 dB/°C. The entire FBG sensing system has an excellent linear response to temperatures controlled with an accuracy of ±0.3°C.