Abstract: Disclosed is a method for making the transition from a hybrid network into an all fiber network. In the preferred embodiment, the first step is to replace an existing fiber optic/coaxial cable conversion device located at a remote node with an optic distribution device. Secondly, a house optical network unit is installed in a living unit. Finally, a downstream optic fiber is installed between the optic distribution device and the house optical network unit.

Abstract: A fiber-coax network (30) includes feeder fiber (14) from a central office/headend (10) to a distribution node (32). At the distribution node, the transmissions are routed and distributed via successively a cable-coax node (16), a first PON node (36), and a second PON node (84). Each PON node comprises one or more passive optic component such as an optic splitter or wavelength division multiplexer (WDM). The cable-coax node provides broadcast CATV to subscribers via a coax distribution network (18) having spaced line extension amplifiers (LEAs) (26) in order to service more subscribers. The first PON node (36) provides switched telecommunication services (including ISDN) to subscribers via distribution fibers (38) which terminate at respective optic network units (ONUs) (40) that are co-located with an LEA (26) and connect to the coax distribution network downstream of the LEA (26).

Abstract: A comb splitting system demultiplexes and/or multiplexes a plurality of optical signal channels at various wavelengths. The comb splitting system has at least two interconnected successive stages of wavelength division multiplexers (WDMs). A WDM of a first stage communicates bands of channels to respective WDMs of the second stage via suitable optical paths. Each of the bands has a plurality of the individual channels that are separated by at least one other of the channels. Each second stage WDM, which is allocated to a particular band, is interconnected to optical paths, each for carrying one or more individual channels. Furthermore, in accordance with a significant feature of the present invention, the bandpasses and bandpass periodicity (free spectral range) associated with the first stage WDM are smaller than the bandpasses and bandpass periodicity associated with the second stage WDMs. The foregoing feature has numerous advantages.

Abstract: An optical communication network includes a novel, passive optical component. This component combines the function of a splitter with the function of a wavelength-division multiplexer. These functions are performed in distinct wavelength bands. In one embodiment, the inventive component is made using silicon optical bench technology.

Abstract: An optically switches relatively low power requirements and a relatively broad operating bandwidth. This switch includes a Mach-Zehnder interferometer (MZI) optically coupled at respective ends to an input coupler and an output coupler. One arm of the MZI includes a thermo-optic phase shifter. The output coupler is an adiabatic 3-dB coupler. In one embodiment, the input coupler is a Y-branch coupler having one input port. In a second embodiment, the input coupler is an adiabatic 3-dB coupler having two input ports.

Abstract: The occurrence and location of a disturbance in the vicinity of a localized portion of an optical fiber are determined based on the recognition that such a disturbance changes the polarization condition of signals backscattered from the disturbed portion. Thus, multiple consistently polarized optical pulses are applied to an input end of the fiber and only signals of a particular polarization that are backscattered from the disturbed portion are abstracted from the input end. An output signal indicative of the disturbance is generated by processing these backscattered signals in accordance with synchronous detection techniques.

Abstract: An optical communication network includes a fiber-optic terminal system (FOTS) coupled to internal optical waveguides (or fibers) situated within a central office or terminal. These waveguides connect to external optical fibers. A new component is provided for optically coupling the FOTS to the waveguides. This component includes planar waveguides, referred to as "main waveguides" formed on a substrate. Each main waveguide is coupled at one end to the FOTS and at the other end to an internal waveguide. Monitor waveguides, also formed on the substrate, are used to transmit OTDR signals to the main waveguides. Wavelength-division multiplexers formed on the substrate are used to couple monitor waveguides to corresponding main waveguides with respect to monitor wavelengths but not with respect to signal wavelengths.

Abstract: An optical communication network includes at least one single-mode fiber, referred to as a "primary fiber," for transmission between a central office and a distribution node, and at least one multiplicity of single-mode fibers, referred to as "distribution fibers," for transmission between the distribution node and a multiplicity of optical network units (ONUs). Transmissions are exchanged between the primary and distribution fibers via at least one optical coupler located at the distribution node. The network is passive in the sense that all monitoring of the transmission media and the ONUs can be performed at the central office, without active intervention at remote locations. The network includes a monitor and a multiplicity of bypass lines by means of which at least a portion of inbound signals from the distribution fibers are transmitted to the monitor without passing through the optical coupler at the distribution node.

Abstract: We describe an interferometric, channel-dropping, optical filter that includes a pair of planar waveguides. The two waveguides are spaced apart by a distance which is periodically varied along the longitudinal axis of the filter in order to effect a periodic optical coupling between them. There are at least three coupling locations, each associated with a coupling constant. The two waveguides have nominally equal effective refractive indices. In preferred embodiments of the invention, the coupling constants decrease symmetrically from the center of the filter toward the ends.

Abstract: An optical communication network includes at least one single-mode fiber, referred to as a "primary fiber," for transmission between a central office and a distribution node, and at least one multiplicity of single-mode fibers, referred to as "distribution fibers," for transmission between the distribution node and a multiplicity of optical network units (ONUs). Transmissions are exchanged between the primary and distribution fibers via at least one optical coupler located at the distribution node. The network is passive in the sense that all monitoring of the transmission media and the ONUs can be performed at the central office, without active intervention at remote locations. The network includes a monitor and a multiplicity of bypass lines by means of which at least a portion of inbound signals from the distribution fibers are transmitted to the monitor without passing through the optical coupler at the distribution node.

Abstract: Disclosed is an optical communication system comprising at least two optical fibers of dissimilar core sizes, joined by a fusion splice. In one embodiment, the larger-core fiber is a communication fiber, and the smaller-core fiber is an erbium-doped amplifier fiber. A taper region is included adjacent the splice. The diameter of the smaller-core fiber increases within the taper region as the splice is approached along the smaller-core fiber. The taper region is substantially free of constrictions. As a consequence of the taper region, the optical losses associated with the splice are relatively low, even when there is relatively high mismatch between the mode field diameters (at a signal wavelength) in the respective fibers.

Abstract: Disclosed is a planar optical waveguide that is manufacturable by the compression molding or embossing of a multilayer film of polymeric material. In one embodiment, the waveguide comprises a core layer of relatively high refractive index included between cladding layers of lower refractive index. The waveguiding channels are bounded by regions where the cladding layers are in contact and from which core material has been excluded.

Abstract: A mode scrambling arrangement for a multimode optical fiber by irradiating the cladding using an ultra-violet light to change the index of refraction of the cladding. The cladding uses a material whose index of refraction is modified in response to ultra-violet light. The exposure time and intensity of the light required is determined by monitoring the mode pattern in the multimode fiber during the irradiation to provide the desired amount of mode scrambling.

Abstract: Distributed region optical sensors for chemical detection are provided by utilizing optical fiber technology. A core is provided with a surrounding region that is permeable to the chemical to be detected. A composition whose optical characteristics are altered upon interaction with the chemical to be detected is provided within the permeable material. This change in optical characteristics allows chemical detection through detection of light guided by the fiber.

Abstract: An optical system, including a waveguide such as an optical fiber, in which optical signals are noninvasively coupled into the waveguide at any point along the length of the waveguide, is disclosed. This is achieved by coupling substantially constant intensity electromagnetic radiation into the waveguide, and then impinging upon the waveguide a directed beam of energy, such as electromagnetic radiation or heat, from an energy source. Alternatively, the waveguide is impinged upon by a combination of an energy beam and a stimulus, e.g., a temperature change. The energy beam, or energy beam and stimulus, induce at least partial absorption of the guided, substantially constant intensity electromagnetic radiation by radiation-absorbing material in the waveguide, to produce the desired optical signal.

Abstract: Disclosed is BeF.sub.2 -based optical fiber. Such fiber can have, in addition to low loss, other advantageous properties. For instance, BeF.sub.2 -based dispersion shifted single mode fiber can have lower core-cladding index difference and larger core diameter than the corresponding SiO.sub.2 -based fiber, and BeF.sub.2 -based graded index multimode fiber can have larger bandwidth than the corresponding SiO.sub.2 -based fiber. The inventive fibers have a core and a cladding containing at least 30 mol % BeF.sub.2, and may contain up to 40 mol % of AlF.sub.3, and one or more members of the group consisting of NaF, KF, MgF.sub.2, CaF.sub.2, PbF.sub.2, PF.sub.5, and SiF.sub.4. An exemplary and currently preferred glass has nominal composition (in mol percent) 30KF-(15-x)CaF.sub.2 -xPbF.sub.2 -10AlF.sub.3 -45BeF.sub.2, with x.ltoreq.15. Single mode fibers according to the invention have minimum total dispersion in the range 1.5-2.0 .mu.m, and typically have 0.25%.ltoreq..DELTA..sub.esi .ltoreq.0.6%, and 2.5 .mu.m.

Abstract: Single mode and multimode silica-based optical fibers having a down-doped outer cladding are disclosed. The outer cladding material is derived from a preexisting silica tube that comprises an amount of index-lowering dopant, typically F or B, sufficient to result in an effective refractive index of the material that is at least about 0.001, preferably at least 0.0025, lower than the refractive index of SiO.sub.2. Single mode optical fiber according to the invention typically requires a smaller amount of deposited cladding material than an equivalent prior art fiber, and thus can be produced more economically. Multimode optical fiber according to the invention may have lower core doping or higher NA than equivalent prior art fiber. Down-doped substrate or sleeve tubes advantageously are produced by a gel process.

Abstract: The application pertains to fiberguide systems comprising signal sources having center wavelengths near an absorption peak in the loss spectrum of the fiber, with the systems having a link length of several km, preferably at least 5 km. The resulting "filtering" of the signal can be used advantageously. For instance, the repeater spacing of a LED-based multimode system can be increased if fiberguide having an absorption peak of appropriate strength located above the minimum chromatic dispersion wavelength of the fiber is used, and if the LED center wavelength is chosen to exceed that wavelength by a small amount. In particular, in silica-rich fiberguide, absorption peaks due to OH typically occur at about 1.24 .mu.m and 1.39 .mu.m, and the wavelength of minimum chromatic dispersion can be about 1.3 .mu.m. In such systems according to the invention, the total fiber loss at 1.39 .mu.m is typically at least about 0.

Abstract: In a double-clad, single mode fiber with depressed inner cladding, reduced losses at the longer wavelengths are realized when the ratio of the radius of the inner cladding to the radius of the core is at least 6.5 to 1.

Abstract: The inventive multimode fiber has total loss at an operating wavelength of at least about 0.8 db/km, typically not more than 5 db/km. At least 0.3 db/km, preferably 0.5 db/km, of the loss is due to the presence in the fiber of radially nonuniformly distributed attenuation centers, with the concentration of the centers differing by at least about 10% between the concentration minimum and the maximum. The resulting differential mode attenuation can lead to fiber having larger bandwidth than analogous fiber without differential attenuation. Preferred distributions of attenuation centers have the concentration maximum either at or near the fiber axis, or at or near the core/clad interface. Preferred attenuation centers are absorbers, with OH being a preferred absorber.