Abstract: A communication system includes plural nodes interconnected with an optical transmission medium capable of carrying plural bands of optical channels. A device at each node is coupled to the medium for dropping one or more bands, adding one or more bands, and passively transmitting other bands such that a pair of nodes can communicate directly using a band common to the respective bands. One band of the bands associated with each of a first set of nodes overlaps with one band of the bands associated with each of a second set of nodes. Multiple overlapping bands provide a high level of wavelength termination diversity. An optical management bus system and method connects plural hybrid optical/electrical cables between transmission equipment and optical modules which connect to network fibers to provide a set of electrical connections that can be used to determine optical interconnections in an optical shelf configuration.

Abstract: A communication system includes plural nodes interconnected with an optical transmission medium capable of carrying plural bands of optical channels. A device at each node is coupled to the medium for dropping one or more bands, adding one or more bands, and passively transmitting other bands such that a pair of nodes can communicate directly using a band common to the respective bands. One band of the bands associated with each of a first set of nodes overlaps with one band of the bands associated with each of a second set of nodes. Multiple overlapping bands provide a high level of wavelength termination diversity. An optical management bus system and method connects plural hybrid optical/electrical cables between transmission equipment and optical modules which connect to network fibers to provide a set of electrical connections that can be used to determine optical interconnections in an optical shelf configuration.

Abstract: A method for improving modal bandwidth in computer networks using multimode optical fiber and laser sources is disclosed in which an annular beam is generate by the laser source, thus preventing center fiber transmission modes from reaching the detector. This prevents or lessens a pulse-splitting effect at the detector. The annular beam is generated preferably by configuring a vertical cavity surface emitting laser to have a center totally-reflecting block of 5-7 microns to generate a substantially dark-centered beam.

Abstract: A control circuit for a laser diode includes a power controller and a wavelength controller. The power controller adjusts a bias current to the laser diode to change the power output of the laser diode. The power change can have a corresponding wavelength shift effect on the nominal operating wavelength of the laser diode. The wavelength controller compensates for the wavelength shift such that the laser diode maintains operation at the nominal wavelength. The circuit provides for electrical control of the laser output power without the need for a costly and bulky optical attenuator. The circuit also provides wavelength control to compensate for the relationship between laser diode operating temperature and wavelength.

Abstract: A method of improving modal bandwidth in computer networks using multimode optical fiber and single mode sources is disclosed in which the optical signal from a center of the optical fiber is prevented from reaching the detector. This is accomplished according to a number of different techniques including the use of opaque spots on the fiber media/fiber couplers or the use of dark-cored fiber couplers. These configurations prevent pulse splitting that occurs in single mode source/multimode fiber systems by preventing light from the multimode fiber's center from interfering with the detector. When this is achieved, the detector is insulated from the effects of pulse splitting, supporting increased data rates by increasing the modal bandwidth.

Abstract: A method for improving modal bandwidth in computer networks using multimode optical fiber and single mode sources is disclosed in which the optical signal from a center of the optical fiber is blocked from reaching detector. This is accomplished according to a number of different techniques including the use of opaque spots on the fiber media/fiber couplers or the use of dark-cored fiber couplers. These configurations prevent pulse splitting that occurs in single mode source/multimode fiber systems by preventing light from the multimode fiber's center from interfering with the detector. When this is achieved, the detector is insulated from the effects of any pulse splitting, supporting data rates of greater than one GBPS by increasing the modal bandwidth.

Abstract: The input bandwidth of a data transfer device is increased by altering the conventional memory arbitration method in which a data cell is stored and a data cell is forwarded during each data transfer cycle. The input data rate is monitored and when the input data rate exceeds the maximum average throughput of the memory, the outcome of the memory arbitration cycle is changed so that the memory arbitration cycle consists of two stores (memory write operations) instead of one store and one forward (memory read operation.) In effect, the input memory arbitration process steals cycles from the output memory arbitration process when the input load exceeds that of the maximum average memory throughput. In accordance with one embodiment, the input data rate is monitored by examining input port FIFO buffers for the presence of data cells waiting for storage.

Abstract: A switchable interface for conveniently coupling a network station of the CSMA/CD type to a network having any of a variety of communication media. The invention provides a single interface connector through which connection may be made directly to a twisted-pair medium, using the 10BASE-T protocol, or to a medium of a different type, through an AUI protocol and an appropriate media attachment unit. The interface connector has pin assignments chosen to minimize adverse effects of misconfiguring the station by connecting to a network having a protocol that is different from the one selected in the switchable interface. In one form of the invention, the switchable interface has the ability to determine the protocol being used by the network to which it is connected, and to switch the interface accordingly. Use of the common interface reduces station equipment cost and provides for increased user convenience, since only a single connector is needed to connect to a variety of media types.

Abstract: Method and apparatus for automatically switching an Ethernet station interface to choose between two protocols and, possibly, two external connector configurations, to adapt the station automatically to the correct one of two communication media types, such as the twisted-pair medium served by the 10BASE-T protocol, and other media types, served by the attachment unit interface (AUI). The invention continually tests for proper operation in the currently selected protocol, and switches to the other protocol upon failure of a test. If one of two available external connectors is used to connect the station to a network, the invention chooses between the connectors automatically, such that manual switching between them is not required.

Abstract: A duplicate address condition in a computer network may be detected by a station of the type for attachment to a computer communications network, the network capable of maintaining communications among a plurality of stations, the station having means for receiving a frame, the frame having a source address field and a frame control field; means for maintaining an individual address of the station; means for maintaining a source address list of address, the source address list not containing the individual address; means for determining that a contents of the source address field in the frame matches at least one address in the source address list; means for determining that the frame control field of the frame has a predetermined contents; and, means, responsive to the source address of the frame matching at least one address in the source address list and the frame control field of the frame having the predetermined value, for setting an indicator that a duplicate address condition exists.

Abstract: RingOp/Claim oscillations due to duplicate addresses and transmit aborts are avoided by using token preserver frames to reset the TVX timer in a station. A communications network having a plurality of stations capable of transmitting frames onto the network, and the stations capable of detecting transmission on the network, and the stations capable of taking predetermined action in the absence of detecting the transmission for a predetermined first time interval, and a first timer for measuring the predetermined first time interval. Measuring a second predetermined time interval, the second predetermined time interval being chosen to be less than the first predetermined time interval; transmitting a reset frame onto the network by a selected station at time intervals substantially equal to the second predetermined time interval, and the reset frames being capable of causing a station to reset the first timer to a beginning value. The network may be a token controlled ring.

Abstract: An output controller in a repeater node for controlling data transfers in a data communication system in which each node is operated by an independent local clock. Nodes will occasionally delete idle bytes from a preamble to recenter an elasticity buffer. The output controller performs a process that requires the elasticity buffer to be progressively more full before deleting another idle byte from the preamble. Transmission of the start of a subsequent frame is delayed and additional idle bytes are transmitted when the number of idle bytes being transmitted is at or below a certain threshold. Multiple thresholds are utilized so that the amount of the delay can be adjusted.