Abstract: In accordance with the invention, an optical fiber system is provided with a tapered fiber device for filtering, wavelength shift detecting, or switching. Specifically, applicant has discovered that a multiclad single mode optical fiber with a fundamental mode cutoff can be tapered to form a compact component useful in optical fiber systems, e.g. a filter in telecommunications systems, a wavelength shift detector in sensing systems, or a switch in any optical system.

Abstract: An optical device includes: a first dielectric slab waveguide having an effective refractive index N.sub.1 ; a second dielectric slab waveguide having an effective refractive index N.sub.2 ; and a third dielectric slab waveguide having a length 1 and an effective refractive index N.sub.3, the third dielectric slab waveguide being formed between the first dielectric slab waveguide and the second dielectric slab waveguide so as to connect the first dielectric slab waveguide with the second dielectric slab waveguides optically; wherein the length I and the effective refractive index N.sub.3 substantially satisfy following equations; ##EQU1## where .lambda. is a free-space wavelength of light traveling in the optical device and the light travels from the first dielectric slab waveguide to the third dielectric slab waveguide at an incident angle .THETA. in a single mode.

Abstract: In accordance with the invention the birefringence induced by compressive strain in silica waveguides on silicon substrates is compensated with a high index patch--such as silicon nitride--placed adjacent the core. The patch is disposed sufficiently close to the core to optically couple with the transmitted optical mode. The patch is preferably wider than the core to intersect the exponential tail of the transmitted optical mode. Such a high index patch preferentially couples TE polarization modes. By choosing an appropriate length for the patch, both strain and bend birefringence can be compensated.

Abstract: A low loss fiber optic coupler of the type wherein a plurality of single-mode optical fibers are fused together along a portion of the lengths thereof to form a coupling region. Each fiber includes a core and a cladding, the lowest refractive index of the fiber claddings being n.sub.2. Each of the output fibers of the coupler further includes a surface region of refractive index n.sub.4 that inhibits the coupling of light to lossy composite modes, n.sub.4 being lower than n.sub.2.

Abstract: Previous efforts to measure polarization dependent loss of optical components have been limited in uncertainty to more than 0.01 dB. This is because the power meter used in a test set contains polarization dependent loss which adversely affects the final readings. It is here disclosed that an unpumped erbium doped fiber can convert a received polarized signal into unpolarized amplified spontaneous emission of a longer wavelength if the fiber is of sufficient length to absorb the received signal. By locating the inventive unpumped erbium doped fiber upstream of the power meter of a test set, the polarized signal to the power meter is coverted to an unpolarized signal and, therefore, the polarization dependent loss of the power meter can not influence the measurement obtained.

Abstract: An optical transmitter (1) comprises a semiconductor laser optical source (14) housed in an optical fibre connector component. An optical baffle (8) such as a short section of optical fibre ensures that only minimal power is emitted to the environment when the transmission fibre (6) is withdrawn from the connector.

Abstract: An optoelectronic device having an optical guide and photodetector integrated on a common substrate is provided with a light coupling means for increasing the absorption of light within the photodetector. This means consists of freeing the lower portion of the guide layer--opposite the photodetector--to bring it into contact with air. The use of air has the effect of repelling the light propagating through the guide layer towards the absorbent layer of the photodetector thereby increasing the photodetector efficiency.

Abstract: An optical modulation method operable in an optical transmission path using an optical fiber, wherein an optical fiber bending region is formed by bending a portion of the optical fiber into a U shape having a predetermined bending width. A bending width set point is set in correspondence with a predetermined inclined portion of a characteristic curve representing a dependency ratio of insertion loss of light propagating in said optical fiber bending region relative to the bending width thereof, said predetermined inclined portion of said characteristic curve being located between a predetermined maximum and minimum portion thereof. Intensity modulation of light propagating in the optical fiber is performed using a signal to be transmitted by adjusting the bending width of the optical fiber bending region in correspondence with the signal to be transmitted with reference to the bending width set point as a center.

Abstract: An optical fiber connector element comprises a ferrule and an optical fiber stub secured within a through passage of the ferrule. The optical fiber stub comprises a core, an inner cladding having a diameter no more than six times the core diameter and a refractive index less than the core refractive index, and an outer cladding having a refractive index greater than the inner cladding refractive index and less than or equal to the ferrule refractive index. A length of the outer cladding is in intimate contact with the ferrule. A rearward part of the ferrule passage may have an inner diameter greater than the outer diameter of the fiber stub, and a plastic plug having a through passage for receiving the fiber stub may be located in the rearward part of the ferrule passage. The plastic plug has a refractive index equal to or greater than the outer cladding refractive index and less than the ferrule refractive index.

Abstract: A waveguide structure includes a substrate, a waveguide film, and an overlay material in contact with the waveguide film. The overlay material may also contact the substrate or the film may be disposed between the overlay and the substrate. The overlay material has a higher refractive index than the waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagating modes supported by the waveguide.

Abstract: The physical properties of thin films can be examined with the aid of polarized light with which the film to be examined is irradiated while the reflected or transmitted light is deflected in the direction of an imaging system, the polarized light having the effect of exciting waveguide modes in the film to be examined.

Abstract: A fiber-optic communication system (10) employs a Fabry-Perot laser (14) that launches its output onto a single-mode pigtail (16) physically coupled to a mode scrambler (22), which is air coupled to a transmission medium consisting of multi-mode fiber-optic cable. Because the mode scrambler (22) divides the laser output power among many modes, the fraction of any reflected light that is coupled back into the cavity of the laser (14) can be made small enough to permit sufficient laser coherence for high-data-rate-transmission.

Abstract: Integrated monomode spatial optical filter and its method of embodiment. The optical filter of the invention for isolating one first optical mode and eliminating second stray optical modes consists of an optical microguide (4) borne by a substrate (2) and having along a plane parallel to the surface (P) of the substrate at least one curved portion (6) whose radius of curvature is such that the losses in the curve of the first and second modes are respectively negligible and extremely high and two light absorbers (8, 10) disposed within a given plane on both sides of the curved portion (6).

Abstract: An output of a light source coupled to an optical fiber is controlled by an apparatus comprising a mode stripper for stripping a first part of the optical signal from the cladding of the optical fiber, means for bending the optical fiber and withdrawing a second part of the optical signal from a core of the fiber downstream from the stripper, means for detecting the second part of the optical signal, and feedback means for using the detected second signal part to control an output of the light source to better linearize an amount of power injected into the fiber.

Abstract: A constricted portion (14) is formed on an optical fiber (6) composed of a core (2) and a clad (4), and one or two belt-like conductive layers (20) elongated in a longitudinal direction of the optical fiber (6) are provided on a surface of the constricted portion (14). With the structure, the device functions as a polarizer which removes a polarized light component having a polarization plane perpendicular to the conductive layers (20). The optical fiber polarizer is suitably inserted in and used with an optical transmission line of an optical communication system and is also suitable for use as a component of an optical isolator.