Fiber optic intensity sensor referenced with a virtual delay line

Abstract

In this work a self-referencing fiber optic intensity sensor using virtual instrumentation is presented. To ensure higher flexibility and dynamic optimization, the use of an optical fiber delay line or an electrical delay line is avoided by implementing a delay line in the virtual domain, preserving the self-referencing and sensitivity characteristics of the proposed optical intensity sensing structure. Results are presented where displacement is measured with an 18 μm resolution demonstrating the concept feasibility.

Remote Interrogation of WDM Fiber-Optic Intensity Sensors Deploying Delay Lines in the Virtual Domain

“…The 0.3% F.S. measurand resolution obtained is better than the values reported in [15], which were around 1.3% F.S., even though lower frequencies are used, of tenths of Hz. Resolution improvement is mainly due to the reflective operation and better R parameter performance of our sensing structure.…”

“…This electro-optical self-referencing solution was verified by modulating the light injected into the network and using a lock-in amplifier and electrical phase-shifters at the reception stage. On the other hand, it was recently reported a virtual delay line deployment [15], but in a Mach-Zehnder interferometric topology in which the optical source was modulated with two different frequencies and based on a power-splitting topology rather than in a WDM approach. The self-referencing parameter was defined as the ratio of voltage values of the optical output sinusoidal wave at a previously defined non-constructive and constructive interference frequency, respectively.…”

Ring Cavity Erbium-Doped Fiber for Refractive Index Measurements

“…They range from the simplest, such as cleaved multimode fiber tips, to the most complex, such as microspheres [ 8 ]. Intensity sensors require signal referencing to eliminate source fluctuations and sometimes there is high signal noise when the sensors are immersed in liquids [ 9 , 10 ]. On the other hand, ring cavity erbium-doped fiber lasers (EDFRLs) use the gain provided by the erbium-doped fiber (EDF) more efficiently, and they also have a cavity free spectral range (FSR) that is twice as large for the same cavity length, compared with linear cavity lasers.…”