Fiber ring interferometer

A birefringent single-mode optical fiber is twisted mechanically in alternating sense on successive half-wave fiber sections. This arrangement, applicable in-line to a fiber, permits continuous adjustment of the state of polarization at the fiber output.

Single-mode fiber-optical polarization rotator.

The invention relates to an inerferometer based on the exploitation of an optical fibre through which both the phase signal which is of interest for the measurements concerned and a reference signal are simultaneously forwarded in order that in the differential measurement the noise introduced by the optical fibre for both thermal and mechanical reasons is ruled out.

Interferometer transmitting the useful phase information through optical fibres

A new follow-up-type laser Doppler velocimeter (FUTLDV) is constructed using single-mode optical fibers The use of optical fibers makes it possible to freely move the sampling volume of the LDV The feedback control system is designed so that the LDV can follow the movement of the object This system gives simultaneously high spatial resolution and wide measurable region The results obtained by the FUTLDV system constructed show the usefulness of this system

Follow-up-type laser Doppler velocimeter using single-mode optical fibers.

An incident light field is applied to the two separate front fiber faces of a pair of identical optical fibers which are initially held in a common plane. One fiber face is always kept stationary. The other fiber face may be moved either laterally in a plane common to the stationary face, or longitudinally into and out of the common plane. The output end of the device comprises two separate rear fiber faces that are held in a common plane. These faces are stationary. There is no lateral or longitudinal motion of one relative to the other. The light emerging from these two faces interferes in the far field. Straight line interference fringes whose spacing depends upon the lateral separation of the rear fiber faces are formed. The fringe modulation, however, depends upon the relative position of the front fiber faces. This modulation changes as one front face is scanned either laterally or longitudinally. The modulation changes with such motion is related to the degree of spatial or temporal coherence of the incident light field.

Fiber optic coherence meter

A new method of measuring the complete optical field distribution (optical field mapping) is proposed and is applied to the measurement of Gaussian beam distribution at its beam waist. This method utilizes an interference technique and uses two single-mode optical fibers as flexible paths. The interference pattern caused by the output beams from the reference fiber and pickup fiber directly gives the relative phase distribution at the input end. For the intensity and phase distribution measurements the experimental ambiguity is as small as 0.1 microm and 1/10 of the wavelength, respectively. Stability of the interference fringe against the distortion of the fiber is also examined experimentally.

Michitomo Iiyama

Papers

Optical field mapping using single-mode optical fibers