Abstract: The method and system of the present invention can be utilized to model aggregate multimedia traffic within a shared transmission medium, such as an ATM network, so that customer expectations can be met and the network can be constructed and utilized efficiently. A total number of different traffic services, as well as a maximum number of sources of each service are specified by a network operator. Next, a quality of service characterization for each service is determined, based upon available standards. Average sojourn time for each service is determined by modeling each Constant Bit Rate (CBR) service as a Renewal Process, each Variable Bit Rate (VBR) real-time service as a multistate Modulated Discrete Process and each Variable Bit Rate (VBR) non-real-time service as an On-Off Process. Sojourn mean times can thereafter be obtained from measurements or published standards.

Abstract: A method and system are provided for calculating the total service capacity for multimedia traffic under aggregate traffic conditions within a shared transmission medium, such as an ATM network. A total number of different types of telecommunication traffic is specified by the network operator or network designer. Each different type of network telecommunication traffic is referred to as a service. Next, each week is partitioned into several busy periods. This partitioning is provided by the network operator and may include multiple days, for example: Monday-Friday; and, Saturday-Sunday. Thereafter, for each busy day described above, the day is further partitioned into several busy periods, each period discernible from a previous period by the level of activity expected within the network at that time. For example, 8:00 a.m.-5:00 p.m.; and, 5:00 p.m.-7:00 a.m. Once again, this information is provided by the network operator or network designer.

Abstract: Various operational measurements of a network element are determined in real time. These measurements are used to determine the call carrying capacity of the elements and the reaction of the network element to various call loads. Models of the network elements are generated from the operational measurements. Using an element's model, the network's reaction to various changes in a particular element can be determined without complex and expensive engineering work.

Abstract: A tool for use in manipulating telecommunications modules comprises a housing having a grip, engagement means for engaging with a module so as to securely grasp the module and a transmitter/receiver unit for transmitting signals to and receiving information from the module. Information received from the module is displayed on the tool. The tool also has a control for allowing a user to request decommissioning of the module to which it is engaged, the tool being arranged to receive a reply from a module indicating that decommissioning is complete. Preferably an interlock mechanism couples an unlocking control on the tool to a key, the interlock inhibiting key until receiving the reply from the module indicating that decommissioning is complete. The tool can also be used to configure a module.

Abstract: A method and system for assessing quality of service for multimedia traffic under aggregate traffic conditions in a shared transmission network, such as an ATM network. A total number of different traffic services as well as a maximum number of sources for each traffic service are specified by a network operator/designer. Next, for each traffic service a specification of peak rate, average idle sojourn time and an average burst sojourn time are determined, either based upon available standards or calculated based upon models of the traffic services. The total available system bandwidth is specified by a network operator/designer. Finally, the number and size of queues utilized for receiving packetized telecommunication traffic within the network are specified.

Abstract: The present invention is based on a tri-cellular grouping of three identical cells. Each cell of the tri-cellular group is driven by a directional antenna that radiates the cell from the center of the group. Multiple tri-cellular groups make up a cellular system having three axes at 0.degree., 120.degree., and 240.degree.. Each axis is comprised of seven total layers, one layer being a repeat of another of the layers. The 512 available system PN offsets are divided up into three groups of 24 offsets, one group for each axis. Each PN offset group is reused only in the direction to which it is assigned.

Abstract: A pulsed optical signal (13) of a network (23) is monitored to obtain eye measurement data as a means of obtaining an indication of signal degradation. Optical sampling of the optical signal is effected by means of an interferometer (2) in which sampling optical pulses (8) are propagated equally through arms 3 and 4 of the interferometer which include semiconducter optical amplifiers. The optical signal to be monitored is counter propagated through one arm of the interferometer, thereby setting an interference condition of the interferometer by cross modulation in one of the semiconductor optical amplifiers. The output is detected and converted to electrical signals which are processed to obtain the eye measurement data. Parameters defining the quality of the eye are extracted and processed to locate defects occurring within a network by deploying eye monitors at a number of locations. Elements of the network may be controlled using the output parameters.

Abstract: The invention relates to automated testing of equipment items of the electronic, electrical, and optical type over a range of environmental conditions. A testing apparatus operates to vary an operating environment of an item of test equipment between a lower extreme and an upper extreme, and iteratively searches each test parameter for a peak response. The peak response is compared with a response limit specified in a customer specification or an international standard. The apparatus assesses a design robustness of the equipment item by comparing a set of measured responses with a maximum range of responses specified in the customer specification or international standard. The apparatus produces a data output for each performance parameter tested, identifying performance parameters which are outside the customer specification, or which have insufficient design robustness.

Abstract: The gain provided by an erbium amplifier is stabilised by spectrally selective optical feedback to make the amplifier lase. The resulting laser emission is extracted from the amplifier output using a Mach Zehnder with matched Bragg reflectors in its two interference arms. The extracted light may be used for supervisory purposes. Part of the laser cavity defining feedback may be provided by the Mach Zehnder by arranging one of its Bragg reflectors to be displaced with respect to the other.

Abstract: To decode an attenuated multi-level signal (42) in a receive interface (120) of communication apparatus, first (134) and second (150) diode pumps co-operate with a biasing chain to ensure that threshold reference levels used by respective positive (52) and negative (54) data comparators are dynamically adjusted to a level dependent upon the attenuated multi-level signal (42) applied to the diode pumps. Particularly, a voltage divider (138-144) acts dynamically to bias differential inputs to the respective positive (52) and negative (54) data comparators, with a ratio between a biasing chain of resistors (138-144) and a common input resistor 128 determining the threshold reference levels used to assign logical levels for the reconstruction of symbols encoded within the multi-level signal (42).

Abstract: A method and system are provided for calculating the simultaneous service capacity for multimedia traffic under aggregate traffic conditions within a shared transmission medium, such as an ATM network. A total number of different traffic services as well as a specification of the peak rate, average idle sojourn time and an average burst sojourn time are determined, either based upon available standards or calculated based upon models of the traffic services. The total available system bandwidth is specified by a network operator/designer. The number and size of queues utilized for receiving packetized telecommunication traffic within the network are also specified. The length and time of a busy period specified by the network operator/designer, a maximum acceptable packet loss rate and the probability that a user will access the network during the busy period are also specified.

Abstract: A method of avoiding phase discontinuities between adjacent sections of a long Bragg grating written section-by-section in an optical fibre uses masks with alignment parts additional to their writing parts. Each alignment part is a replica of a portion of the writing part of the adjacent mask. The writing of the Bragg grating produces an associated absorption grating and so, for light directed in series through the alignment part of the mask and the already-written previous section of the grating, transmission is at a maximum when the mask is moved into exact registry. Fine adjustment of mask position is made to find this condition before writing with this mask is commenced.

Abstract: A modular electronic assembly comprises an electronic circuit module package having electrical contacts and a carrier having a socket for receiving the package. Lever arms pivotally mounted on the carrier retain the module in the socket in their closed position and eject the module from the socket in their open position. The lever arms also carry electrical contacts for engaging corresponding contacts on the module so as to provide electrical connection thereto. The assembly may be mounted in a housing comprising first and slidably engaging portions such that the size of the housing is adjustable.

Abstract: The invention seeks to provide an improved method and apparatus for detecting thresholding errors in a digital signal recovered from a transmitted signal, wherein a derived threshold error signal varies linearly with the threshold error. Extraction of a threshold error signal linearly related to the actual threshold error enables increased speed of reaction of a threshold control circuit.

Abstract: Interference on a differential signal received at a first input to a digital data system processor is minimised or cancelled by summing a weighted portion of a local field signal with the differential signal. The local field signal may be a common-mode signal from the same line as the differential signal received at a second input. Weight may be a complex weight which shifts the local field signal in amplitude and phase. A weight control signal is derived from a comparison processor which compares the processed outputs of signal processors. Signal processors are preferably Discrete Multi-tone processors. Several iterations of this technique may be performed to establish an accurate weighting value.

Abstract: A control system for an etalon arrangement 4, in an optical transmission system involves applying a dither to a laser 1 upstream of the arrangement, monitoring the output of the arrangement, and using a control means 3 to lock the laser frequency to the etalon arrangement response, or vice versa. The control means operates on the basis of a ratio of derivatives of the monitored output with respect to wavelength, to enable locking to a point on the response curve, independent of power variations.

Abstract: A power line communications system has at least one power line upon which noise level varies with time. The system determines quiet periods when noise upon the line is at a reduced level and transmits one or more data packets within the quiet periods, so as to increase data throughput in the system.

Abstract: A frequency selective noise reduction circuit and finds application in receiver demodulator arrangements in mobile telecommunication base stations. A receive signal is divided into two paths. One path includes a Phase Lock Loop circuit (PLL) which is employed to identify noise. The noise signal is inverted and then combined with the other signal.

Abstract: A transformer-coupled mixer circuit including dc voltage supply; and four transistors, arranged as a first transistor pair and a second transistor pair. Each transistor pair has a first transistor and a second transistor and each transistor has a base, a collector and an emitter. The emitter of the first transistor in each transistor pair is connected to the collector of the second transistor in that transistor pair, and the emitter of the second transistor in each transistor pair is connected to a current sink. The circuit also comprises a transformer, having a set of primary windings and first and second sets of secondary windings, the first set of secondary windings being connected in series with the emitter of the first transistor in the first transistor pair and the second set of secondary windings being connected in series with the emitter of the first transistor in the second transistor pair.

Abstract: A progressive method of writing a long grating in a substrate using a pulsed interference fringe pattern. The substrate is moved through the fringe pattern while being continuously illuminated with light of a different wavelength to produce a diffracted beam whose phase is monitored to produce a control signal that regulates the pulsing of the writing beam to ensure that the fringe pattern is present only when it is in correct registry with the grating being written.