Khotiaintsev et al. [85] demonstrated the use of a twin-core fiber with an
integrated coupler as a small-sized probe for invasive laser Doppler anemometry.
Parasitic phase modulation due to external disturbances was reported to be
greatly attenuated because of the integrated design. Wosinski et al. [86] in 1994
proposed the use of a dual-core fiber with different strain and temperature
dependencies for the two cores for monitoring strain in, for example, composites.
Changes in temperature and/or strain introduce refractive index changes that
can be detected with, for example, fiber Bragg gratings inscribed in the cores.
Strain and temperature are then easily obtained from two independent
equations.
The sensor examples so far cited employ dual-core fibers. ...