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Proceedings Paper

Polarization Preserving Fiber-Optic 2X2 Directional Coupler (PPFDC)
Author(s): Shigefumi Masuda; Terumi Chikama; Takashi Touge
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Paper Abstract

A low-loss, wide band, compact, polarization preserving, fiber optic directional coupler (PPFDC) is developed for use in future coherent optical fiber transmission systems or gyroscopes. The PPFDC is made of two 200 μm diameter sapphire ball lenses, a half-mirror and four conical alumina-ceramic ferrules with flat reference plane to preserve polarization at the connection of the fibers. Built-in thermal stress change in the fiber is minimized, because the fiber is polished only for the short length within the straight ferrule. The optical and mechanical axes are tilted, so cross-talk light from the fiber endfaces or lens surfaces is avoided. The optical directivity of the PPFDC is over 50 dB and return loss is over 40 dB in the 1.3 μm wavelength range. The excess loss is under 1 dB in the 1.2 to 1.4 μm wavelength range. The extinction ratio is over 25 dB. The length of the coupling region of the PPFDC is about 1 mm including the two ball lenses and half mirror. Spectral line widths of a fiber interfaced DFB laser diode are measured by a self delayed homodyne detection scheme, using the PPFDC. Experimental results of a novel polarization preserving fiber-optic gyroscope using a phase modulating PPFDC showed reasonable sensitivity and stability. These experimental results verified the above mentioned characteristics of the PPFDC.

Paper Details

Date Published: 31 October 1985
PDF: 8 pages
Proc. SPIE 0568, Coherent Technology in Fiber Optic Systems I, (31 October 1985); doi: 10.1117/12.949855
Show Author Affiliations
Shigefumi Masuda, Fujitsu Laboratories, Ltd. (Japan)
Terumi Chikama, Fujitsu Laboratories, Ltd. (Japan)
Takashi Touge, Fujitsu Laboratories, Ltd. (Japan)


Published in SPIE Proceedings Vol. 0568:
Coherent Technology in Fiber Optic Systems I
Virginia A. Ormiston; Frederic Quan, Editor(s)

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