Low-Loss Photonic Crystal Fiber Interferometers for Sensor Networks

This work addresses important issues of photonic crystal fiber (PCF) interferometers built by fusion splicing: high insertion loss, low mechanical strength, and complex multiplexing schemes. We have found that by decreasing the length of the collapsed region in these interferometers, the overall insertion losses diminish (down to 0.7 dB) without compromising their performance and mechanical strength. To multiplex such interferometers, we have used the frequency-division-multiplexing technique combined with a simple fast Fourier transform demodulation method. To avoid crosstalk between the interferometers, we have calculated the optimal relationship between their periods. The results reported here may allow the development of functional and competitive PCF devices or PCF-based sensor networks and can be adapted to multiplex any other optical fiber sensors that exhibit sinusoidal patterns.