Fiber optic attenuator

Arto Karppinen, Harri Kopola, Risto Myllylä

Research output: Contribution to journalArticleScientificpeer-review


Several possibilities based on the principles of scattering and polarization of light in liquid crystals (LCs) and PLZT ceramics were studied for the replacement of mechanical shutters and attenuators in optical instruments.
A scatter-mode LC was selected as the active material, and two modules were developed for fiber optic attenuator applications. In the first, the light transmitted through an optical fiber (input fiber, Φ100/140 μm) is collimated to a beam using a graded-index microlens (0.25 P, Φ1.8 mm).
This beam penetrates two LC films (7 × 12 mm2) and is received by a microlens at the output fiber. The second, for large-diameter fibers (Φ400 μm), employs conventional aspherical lenses to optimize the fiber-to-fiber coupling instead of microlenses. Components were built for both Φ100- and Φ400-μm fibers. The maximum transmission is up to 70% and maximum contrasts 10,000:1 (632.8 nm), 2000:1 (830 nm), and 700:1 (905 nm).
The rise time is typically less than 1 ms and the decay time less than 5 ms, given a temperature above + 20°C. The contrast remains high from 0 to + 50°C. Both components function with ±100VAC.
Original languageEnglish
Pages (from-to)104-110
JournalJournal of Electronic Imaging
Issue number1
Publication statusPublished - 1992
MoE publication typeA1 Journal article-refereed


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