Effect of MMF stub on the sensitivity of a photonic crystal fiber interferometer sensor at 1550 nm

• A photonic crystal fiber based Mach–Zehnder interferometric sensor is reported.
• It is used to sense the temperature, refractive index and liquid level at 1550 nm.
• The multimode fiber is used which acts as a mode coupler.
• The evidence of interferometric pattern of this sensor is novel, to our knowledge.

A simple photonic crystal fiber (PCF) based Mach–Zehnder interferometric sensor is reported for sensing the refractive index and level of liquid. The sensing head is formed by all-fiber in-line single mode–multi mode–photonic crystal–single mode fiber structure using the fusion splicing method. The interferometric pattern, observed in the PCF interferometer using monochromatic source and temperature sensing arrangement, is novel and reported for the first time to the best of our knowledge. The refractive index sensitivity of the interferometric device is increased by using multimode fiber. The output intensity at the end of lead-out single mode fiber decreases with increase in refractive index of surrounding. The index sensitivities of the interferometric devices are 440.32 μw/RIU, 267.48 μw/RIU and 195.36 μw/RIU with sensing length 2.10 cm, 5.50 cm and 7.20 cm respectively. A 7.20 cm longed PCF sensor exhibits liquid level sensitivities −1.032 μw/cm, −1.197 μw/cm, and −1.489 μw/cm for three different liquid respectively.