Optical time-division multiplexer using optical fiber for phase adjustment
AssigneeOki Electric Industry Co., Ltd.
InventorKozo Fujii
Life of this patent
Estimating the term…
Abstract
An optical time-division multiplexer branches input light into a plurality of optical paths with different optical lengths. At least one path includes a section of optical fiber with an optical length that is adjustable by physical stretching. The input light is separately modulated on each optical path, and the modulated light signals are recombined into a multiplexed output light signal. Adjustment of the optical length of the optical fiber can compensate for changes in input wavelength and adjust the phase of successive pulses in the multiplexed output signal to provide a π-radian shift that enables long-haul optical transmission.
Claims10
An optical time-division multiplexer that branches input light into a plurality of optical paths having different path lengths, modulates the input light propagating on each optical path by a signal to be transmitted, and combines the modulated light from the optical paths into an output light signal, wherein:
- the optical time-division multiplexer comprises a substrate;
- at least one of the optical paths includes a section of optical fiber functioning as an optical path length adjustment section;
- both ends of the optical fiber comprising said optical path length adjustment section are fastened to the substrate;
- said optical paths include spatial sections in which the branched input light propagates through a space having a refractive index different from a refractive index of the optical fiber;
- the optical time-division multiplexer has means for altering the optical length of the optical fiber in the optical path length adjustment section;
- and
- said means for altering the optical length of the optical fiber comprises a member mounted on the substrate, rotatable in a plane parallel to the substrate, having a surface that presses against the optical fiber, bending the optical fiber by different amounts depending on the rotational position of the member.
A method of generating a time-division multiplexed optical signal by branching input light onto a plurality of optical paths, modulating the light separately on each optical path, and recombining the light from the optical paths, comprising the steps of:
- providing a section of optical fiber on at least one of the optical paths;
- and
- adjusting an optical length of the optical fiber, thereby adjusting a phase relationship of the recombined light, by turning a rotatable member that presses against the optical fiber, thereby applying lateral pressure to the optical fiber to stretch the optical fiber, the rotatable member having a varying radius.
An optical time-division multiplexer comprising:
- an input adapted to receive input light;
- a half-mirror adapted to branch said input light onto a first spatial optical path and onto a second spatial optical path;
- a modulator adapted to modulate said light on said first spatial optical path;
- a mirror adapted to reflect said modulated light;
- a section of optical fiber in said first optical spatial path adapted to receive said reflected light, said section of optical fiber being adapted to adjust a difference in optical path length between said first spatial optical path and said second spatial optical path;
- and
- a rotatable member that presses against said section of optical fiber, wherein rotation of said rotatable member generates a lateral pressure on said section of optical fiber.
Dependencies are inferred from the claim text.