Abstract: A gain equalizer which equalizes gain versus wavelength characteristics of an optical amplifier. The gain versus wavelength characteristics of the optical amplifier include first, second and third gain peaks in a wavelength band with the second gain peak being between the first and third gain peaks. The optical amplifier amplifies an input signal in accordance with the gain versus wavelength characteristics to produce an output signal. The gain equalizer includes first, second and third optical filters having first, second and third transparency characteristics, respectively. The first, second and third transparency characteristics are periodic waveforms having different periods related to the wavelength difference between the first and third gain peaks. The second transparency characteristic is a periodic waveform having a period equal to 1/(2n) of the period of the waveform of the first transparency characteristic.

Abstract: This invention discloses an optical detector system, including a photo detector generating an electrical current according to light received thereby, voltage terminals at opposite sides of the photo detector for connection to a voltage source, a pair of resistors each connected between a voltage terminal and the respective side of the photo detector, a pair of matched amplifiers each having an input connected to the juncture between the respective resistor and the respective side of the photo detector, each of the matched amplifiers having an input resistance substantially less than that of the resistor to which it is connected, and an output circuit combining the outputs of the matched amplifiers.

Abstract: The fiber optic receiver disclosed herein is adapted to receive optical signals which are digitally modulated between an "ON" state in which light is being transmitted and an "OFF" or dark state. The analog output signal of a photodetector is thresholded to obtain a binary electrical output signal and is also sampled during the binary state corresponding to the "ON" received signal. A liquid crystal element is energized as a function of the sampled amplitude thereby to establish a feedback loop driving the sampled amplitude toward a preselected level providing predictable skewing of transitions in the binary output signal.

Abstract: In an optical network through which data is transmitted as a stream of bits during successive bit periods by an optical source with a given optical center frequency, to a receiver for detecting a frequency baseband, interferometric noise power, in particular incoherent beat noise power, is minimized by causing a variation in the center frequency of the source such as to cause a redistribution of the incoherent beat noise power from the baseband to higher frequencies, thereby reducing the noise in the baseband.

Abstract: The invention provides an optical time division demultiplexing apparatus which can perform optical time division demultiplexing while compensating for an operating point drift of an optical time division multiplex signal. The optical time division demultiplexing apparatus includes a clock signal generation element for generating a clock signal for optical time division demultiplexing processing of a received optical signal, and an optical switch for time division demultiplexing the optical signal based on the clock signal from the clock signal generation element.

Abstract: A waveform encoding method and device provide for generating/receiving a power efficient binary intensity modulated optical data signal from a binary source signal which minimizes a time between adjacent pulse transitions and maximizes a pulse peak amplitude for transmission over a low-power wireless infrared link. In generating the signal, the method includes: generating a Q-ary pulse position modulation, Q-PPM, encoded data signal from binary data where Q represents 2.sup.L time slots and L is a predetermined integer representing a predetermined number of binary source bits of the power efficient binary intensity modulated optical data signal; generating an efficient binary intensity modulated signal by increasing the pulse peak amplitude of the Q-PPM encoded data signal by a factor of k, k a predetermined value, and decreasing a pulse width of the Q-PPM encoded data signal by k; and transmitting the efficient binary intensity modulated signal over the low-power wireless infrared link.

Abstract: Apparatus for providing an interface between a triaxial cable and a fiber optic cable for transmission of television signals between a camera and a camera control unit includes first and second converter circuits coupled between the triaxial cable and the fiber optic cable. The first converter circuit converts a first electrical signal received from the triaxial cable to an optical output signal. The second converter circuit converts an optical input signal received from the fiber optic cable to a second electrical signal. The first and second electrical signals each include a plurality of television signals in a frequency division multiplex format. The first converter circuit includes a plurality of bandpass filters coupled in parallel to receive the first electrical signal each of which passes one of the first television signals.

Abstract: The present invention relates to a computer having an infrared communication module for an infrared communication with external equipments. In the computer according to the present invention, since the location of the infrared communication module can change with respect to a main body, the infrared communication between the computer and the external equipments can be performed without changing the position of the computer.

Abstract: An optoelectronic transmitter is provided including a laser diode. A control circuit for driving the laser diode includes a current source which provides a DC bias current to the laser diode, and the laser diode emits an optical signal having an average power determined by the magnitude of the bias current. A voltage regulator establishes a regulated supply voltage which is input to a first reference circuit and a feedback monitor circuit. The first reference circuit establishes a first fixed reference voltage. The feedback monitor circuit includes a monitor device for measuring the optical power emitted by the laser diode, and the monitor circuit establishes a variable monitor voltage proportional to the optical power measured by the monitor device. An op-amp compares the first fixed reference voltage and the feedback monitor voltage, and the output voltage of the op-amp controls the magnitude of the bias current output by the current source.

Abstract: A switch in an optical network unit selectively couples line side ports of the line cards of the unit to individual line circuits in drop cable wiring extending to the customer premises served by the unit. The switchable optical network unit (SONU) permits rapid automated upgrades of service. For example, automatic switching of a line circuit to a line card offering an upgraded service together with automatic provisioning of the SONU to activate service through that line card provides the new upgraded service over the existing line circuit, without requiring a technician to install a new line card or manually connect the line card to the line circuit. If the drop cable to the customer premises includes a primary line circuit and an auxiliary line circuit, the line port can be switched over from the primary line circuit to the auxiliary line circuit to automatically restore service in the event of a failure of the primary line circuit.

Abstract: A method of configuring subnodes, or configuring a system of subnodes, in an optical network ring against both node and fiber failure using an OADM, Optical Add Drop Multiplexer. The network includes a working ring and a stand-by ring and each subnode includes a selective optical filter, an optical 2.times.2 switch and an optical amplifier. The method and the system further include steps of monitoring the inputs and outputs of each subnode at the working and stand-by rings using monitor devices which generate alarm signals upon detection of signal loss at a subnode. As a response to the alarm signal, the state of the subnode, that causes the alarm signal is transferred from a first state into one of a number of possible new states as a function of the generated alarm signal, thereby selecting a switch configuration for the subnode according to the new state to clear the error detected.

Abstract: A communication network system having at least three nodes, which are interconnected by transmission links carrying traffic to and from the nodes. The transmission links are divided into a working ring and a protection ring where the working ring and the protection ring can transmit traffic in opposite directions. A node is able to detect when an error occurs in the surrounding transmission links or the node itself. Each node can, by itself, divert traffic from the working ring to the protection ring and/or from the protection ring to the working ring. A recovery action is performed when the error is healed.

Abstract: An optical access system is shown for use in an office setting including a workstation providing for communication between a network and a computing device, the workstation having a worksurface and at least one network access point coupled to an optical network port. The computing device has a device access point coupled to an optical device port for direct optical communication with the optical network port. The optical access system includes an access station containing the optical network port so that the optical network port is selectively adjustable in a vertical direction by manually repositioning with respect to the computing device and the worksurface. Direct optical communication between the optical network port and the optical device port can be maintained notwithstanding the presence of objects that may obstruct direct optical communication. The optical access system may include a portable computer having a base and a covering lid to which the optical device port is mounted.

Abstract: An optical receiver can operate in response to an input optical signal to produce an output electrical signal. The optical receiver comprises a photo diode (340) for transducing the input optical signal into an electrical signal, a plurality of limit amplifier circuits (310-1, 310-2, . . . , and 310-n) which are connected in series which are connected in series to one another and which have offset compensation functions determined by controllable offset compensation time constants, respectively. The plurality of limit amplifier circuits amplify the electrical signal to produce an amplified and controlled electrical signal in dependency upon the offset compensation time constants controlled. The optical receiver further comprises adjusting circuits (320-1, 320-2, . . .

Abstract: In a WDM fiber-optic network, a unique laser transmitter enables signals to be routed at three hierarchical levels: at one level discrimination among signal paths is based on N WDM wavelength channels, at another level discrimination is based on m AM subcarrier frequency channels, and at a third level discrimination is based on n FM subcarrier frequency channels. Thus, a total of Nmn distinguishable optical channels can be accommodated and a like number of users served. The laser transmitter comprises a broadband, tunable semiconductor laser which includes an intracavity, integrated composite reflector to which a tuning voltage and a FM dither signal are applied, an intracavity gain section to which drive current is applied, and an extracavity, integrated electroabsorption modulator to which an information (e.g., data, voice, video) signal and an AM dither signal are applied.

Abstract: The BER is used as a parameter for evaluating the performance of an optical transmission system. Performance of optical systems is also defined by the Q factor, which uniquely determines the BER in the absence of distortion. The measurements are effected in a point of operation of the channel which gives a value of interest for the Q factor. To this end, the optical SNR is lowered by adding noise over the information signal. A distortion-free Q (Q.sub.DF) and a back-to-back Q (Q.sub.BB) are determined in the same operating point of the system. The distortion penalty for transmitter-receiver pair may be determined by comparing Q.sub.DF to Q.sub.BB. The noise loading technique will allow to investigate if equalizing. The value of OSNRs at the output of a particular system results in equalizing the noise margin in that systems or not.

Abstract: A system and method for providing wavelength division multiplexer is disclosed. The wavelength division multiplexer is for separating an optical signal into a plurality of components. The wavelength division multiplexer includes a splitter and a plurality of isolators coupled to the splitter. The splitter is for separating the optical signal into a plurality of groups. Each group contains a portion of the plurality of components. The plurality of isolators correspond to the plurality of groups. Each of the plurality of isolators is for isolating each component of the corresponding group. In one embodiment, the splitter further includes a splitter input. In this embodiment, the wavelength division multiplexer further includes a filter coupled to the splitter input. The filter is for isolating one of the plurality of components.

Abstract: An infrared (IR) transmitter modulator/receiver controller (TM/RC) encodes downlink serial digital data and precise time synchronization strobes from a host system to provide a downlink modulated serial digital electrical waveform. At least one IR host system transceiver (HST) converts the downlink modulated serial digital electrical waveform to a modulated downlink IR light waveform. At least one IR remote device transceiver (RDT) receives the modulated downlink IR light waveform from the HST. Each RDT is connected to a remote device. The modulated downlink IR light waveform is converted into a corresponding electrical waveform and further demultiplexed into its downlink serial digital data and precise time synchronization strobes. Each RDT provides an uplink electrical and IR modulated serial digital waveform to be received by the HST for conversion to an uplink demodulated serial digital electrical waveform.

Abstract: A system and method are disclosed for demulitplexing closely spaced channels carrying optically encoded data. A composite optical signal having data channels corresponding to center wavelengths .lambda.1, .lambda.2, .lambda.3, .lambda.4, . . . .lambda.n are separated into two composite optical signals of first of which comprises data channels corresponding to center wavelengths .lambda.1, .lambda.3, . . . .lambda.n and a second which comprises data channels corresponding to center wavelengths .lambda.2, .lambda.4, . . . .lambda.n-1, wherein adjacent channels center wavelengths are separated from one another by a distance "d". A periodic multi-cavity Fabry-Perot etalon having a free spectral range of "2d" is coupled to a circulator for launching an input beam. The first of the two composite optical signals carrying channels 1, 3, . . . n is reflected from the input port of the etalon and the second of the of the two optical signals carrying channels 2, 4, . . . n-1 is transmitted through the etalon.

Abstract: A plurality of optical cross-connect switches are freely interconnected to form a mesh type network. At least three of the optical cross-connect switches are switched to form a line-switched ring network, thereby forming a ring/mesh network. Simply by changing the switching logic of the optical cross-connect switches within the ring/mesh network, new rings can be created and existing rings can be modified, thereby providing a great deal of flexibility to make changes to the network as traffic patterns change without incurring hardware costs or significant network downtime. Another advantage of the ring/mesh design approach is that spare capacity within the line-switched ring can be utilized by the mesh network, and spare capacity within the mesh network can be utilized by the line-switched ring, thereby significantly increasing the spare efficiency.