Abstract
We present a simple technique to experimentally determine the optical-path length change with temperature for optical single-mode fibers. Standard single-mode fibers act as natural low-finesse cavities, with the Fresnel reflection of the straight cleaved surfaces being ∼3%, for the laser light coupled to them. By measuring the intensity variations due to interference of light reflected from the fiber front and end surfaces, while ramping the ambient temperature, the thermal sensitivity of the optical-path length of the fiber can be derived. Light was generated by a narrow linewidth, low drift laser. With our fairly short test fibers, we found that it was possible to reach a relative precision of the temperature sensitivity, compared to a reference fiber, on the 0.4%-2% scale and an absolute precision of 2%-5%, with the potential to improve both by an order of magnitude. The results for single-acrylate, dual-acrylate, and copper- and aluminum-coated fibers are presented. Values are compared with analytic models and results from a finite element method simulation. With the aid of these measurements, a simple fiber-interferometer, which is insensitive to thermal drifts, could be constructed.
Highlights
Good knowledge of the thermal sensitivity of single-mode optical fibers can be important for precision optics, where signal variations originating from unintentional changes in optical-path length can be limiting
We present a simple method to determine the thermal sensitivity of optical fibers, which reaches a relative precision between two fibers of 0.4%–2% and an absolute precision of 2%–5%
We have presented a simple experimental method for measuring the thermal sensitivity of single-mode fibers and presented the results for four silica fibers: standard single acrylate, dual acrylate, and copper and aluminum coating, respectively
Summary
Good knowledge of the thermal sensitivity of single-mode optical fibers can be important for precision optics, where signal variations originating from unintentional changes in optical-path length can be limiting. Examples of this include laser stabilization based on fiber cavities, fiber interferometers, fiber sensing, and more broadly in phase-sensitive measurements that use optical fibers.. An alternate method is based on the use of Fiber Bragg gratings connecting to their use as temperature sensors and, more recently, wavelength-sweeping interferometry.10 Another method, presented by Li et al, used very short Fabry–Pérot interferometers (FPIs) made of tellurite and germanite fibers spliced onto a fiber interferometer to measure the thermo-optic coefficient of those glasses. Fiber interferometers already find application as a cheap and simple method to narrow the laser linewidth significantly. environmental disturbances such as thermal fluctuations impose limitations on simple setups, and significant effort regarding isolation or a more sophisticated setup has to be designed to overcome these limitations.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
