Tunable optical filter

Details Tunable optical filter Tunable optical filter

1994-02-22

1996-01-02

Lerner, Martin

Optical: systems and elements

Polarization without modulation

By relatively adjustable superimposed or in series polarizers

359500, 359578, 385 11, G02B 528, G02B 530, G02F 121

Patent

active

054814022

ABSTRACT:
An tunable optical filter of the kind used, for example, in wavelength-division multiplexing (WDM) optical communication systems and tunable source applications, has an interference filter element which is pivotable to adjust the operating wavelength of the filter. In order to reduce polarization dependency as the angle of the interference filter element changes, the light beam to be filtered is passed through the filter element twice, the second time with its polarization state shifted, specifically orthogonal, relative to the polarization state during the first pass. As a result, polarization dependent effects are equalized. The optical filter comprises a pivotally mounted filter element, an input optical fiber for directing a light beam to be filtered through the filter element in a first direction with a first polarization state, optical elements for rotating the polarization state of the filtered light beam and returning the light beam through the filter element (10) a second time, and an output optical fiber for receiving the light beam following passage of the light beam though the filter element the second time. The optical elements may comprise a reflector for reflecting a light beam emerging from the optical filter element to return through the optical filter element in the opposite direction, and a polarization rotator, such as a quarter-wave plate or a Faraday rotator, for rotating the polarization state of the light beam through 90 degrees before passage in the opposite direction.

REFERENCES:
patent: 3401590 (1968-09-01), Massey
patent: 4305046 (1981-12-01), LeFloch et al.
patent: 4502762 (1985-03-01), Anderson
patent: 5272560 (1993-12-01), Baney et al.
patent: 5287214 (1994-02-01), Robertson et al.
R. H. Eather and D. L. Reason et al, Applied Optics vol. 8, No. 2, Feb. 2, 1969, pp. 228-234.

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