Abstract: A transmission system for transmitting data over a channel in the form of a digital signal comprising bits of data, the system comprising an encoder for encoding the data prior to transmission, the encoder producing coding in the form of an overhead, and a decoder for decoding the data after transmission, characterised in that a first portion only of the data is encoded, the second portion remaining uncoded, the system further comprising a partitioner for partitioning the overhead from the uncoded data portion of the signal, after the first portion data has been encoded.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritizing means for prioritizing the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to the bit error rate.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritizing means for prioritizing the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to the bit error rate.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritizing means for prioritizing the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to the bit error rate.

Abstract: A transmission system for transmitting data over a channel in the form of a digital signal comprising bits of data, the system comprising an encoder for encoding the data prior to transmission, the encoder producing coding in the form of an overhead, and a decoder for decoding the data after transmission, characterised in that a first portion only of the data is encoded, the second portion remaining uncoded, the system further comprising a partitioner for partitioning the overhead from the uncoded data portion of the signal, after the first portion data has been encoded.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritising means for prioritising the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to tho bit error rate.

Abstract: The present invention relates to a circuit for driving a solid state optical emitter device such as a laser diode, and in particular a circuit which limits the maximum current which may be drawn through the device. The circuit comprises a current supply path and a current return path to which the optical emitter may be connected, and a current limit device to limit a maximum current that may flow through one of the current paths. The current limit device has a current mirror with an input portion and an output portion, the circuit being arranged so that when a first current flows through the input portion, the second portion is predisposed to supply a second current up to a maximum which mirrors the first current. The maximum current through the paths is thereby limited in accordance with the maximum of the second current.

Abstract: In a Sagnac effect optical fibre gyroscope, which uses a phase nulling photo detection technique to drive a feedback loop controlling one or more non-reciprocal elements connected in series with the coil, a commutating switch reverses the direction of propagation of oppositely directed beams of light directed through the coil and non-reciprocal elements. The null balance is detected as the absence in the photodetector output of any a.c. component in phase or out of phase with the commutation switching. This removes a source of systematic error occasioned by drift in optical parameters of unbalanced components.

Abstract: In a Sagnac effect optical fibre gyroscope a commutating switch (SW) is included immediately before the Sagnac coil (C). Operation of the switch synthesises turning the coil upside down. This provides the advantages of producing an a.c. signal in response to a constant rotation rate and in certain arrangements remove a source of systematic error occasioned by drift in optical parameters of unbalanced components.

Abstract: A termination for an optical fibre is formed with an integral lens for producing an expanded parallel light beam. A pair of terminations provide an optical coupler for connecting between a corresponding pair of optical fibres.

Abstract: In a closed-loop multiple data terminal data transmission system, each message includes in addition to a message portion, a prefix portion having at least the address of the terminal for which the message is intended. When such a message reaches a data terminal its address is checked, and if not for that terminal, the prefix and the message portions are repeated along the loop. If the message is for the terminal only the prefix is repeated along the loop, the message portion being retained at the intended terminal. The prefix with no attached message eventually reaches the originating data terminal where its arrival indicates that the message has reached its destination and that the loop is intact.

Abstract: An optical fiber coupling element in which a short length of optical fiber is placed in a glass sleeve with one end of the fiber projecting from the sleeve. The glass sleeve is collapsed onto the fiber, and a watch jewel is fitted over the fiber end. The other end of the sleeve is flared to facilitate the insertion into it of a second fiber. The sleeve and jewel are sealed into one end of a ferrule.

Abstract: An optical fiber connector in which each fiber is terminated by a coupling element comprising a cylindrical transparent body having a concave reflector on one end facing into the body and a circular reflector on the opposite end facing the concave reflector. The circular reflector has a diameter less than that of the cylindrical body and is concentric therewith. This arrangement has the advantage that the main focussing elements are reflectors and therefore require far less curvature than lenses.

Abstract: An optical fiber coupler comprising a glass sleeve having a link piece of single material glass optical fiber having a refractive index higher than the sleeve mounted in a central section of the sleeve. The central section of the sleeve is collapsed to secure the link piece therein, leaving portions of the sleeve beyond the link piece of sufficient cross-section to freely receive optical fibers therein to be optically coupled. An index matching adhesive is used to secure the fibers in the sleeve abutting the link piece.

Abstract: Optical sensors may be arranged to give transmission or reflection of signals along optical fibers depending on the quantity to be measured. The outputs of several sensors may be simply multiplexed onto a single fiber (or pair) by putting a different delay line in series with each sensor. Similarly optical filters can be used separately or combined with the delay lines and/or space division multiplexing can be used to increase the number of sensors. Local frequency modulation of the sensors offer an additional means of multiplexing.

Abstract: An optical fibre data transmision system in which some terminals at least act as repeaters for received data. Each terminal is allotted a specified transmission time. Terminals are provided with optical fibre by-pass arrangements in case a repeating terminal fails.

Abstract: A process is disclosed for manufacturing a lens termination for an optical fiber using laser machining to form a cavity which centers the fiber in the termination.

Abstract: A connector for coupling a plurality of pairs of single optical fibers is disclosed. A pair of optical fiber terminations abut in a V-groove. Each termination comprises a set of more than three cylinders closely packed side-by-side to provide a plurality of interstitial apertures therebetween into which single fibers are individually inserted. Because the two terminations are positioned in the V-groove, the fibers in one termination will be accurately aligned with corresponding fibers in the other termination.

Abstract: A laser stud mount wherein one terminal connection is provided by the stud and the other by a strip line. One embodiment includes a light guide extending through the stem of the stud mount or along the surface of the stud base for monitoring the light output from the back end of the laser. The monitored light from the back end of the laser can be used to regulate the laser drive.

Abstract: Misregistration and losses between the ends of coupled optical fibre-bundles are reduced by tapering the fibre ends. The ends are etched to remove a portion of the outer cladding glass around each glass core. The tapered ends are inserted into a low refractive index glass tube and drawn down in the tube to form a solid core glass zone. The solid end is polished to facilitate coupling to another bundle.