A method and apparatus redundantly store data, in particular video data objects, in a distributed computer system having at least three processor systems, each processor system being connected in point to point two way channel interconnection with each other processor system. The data is stored in a redundant fashion both at the computer system level as well as the processor system level. Accordingly, the failure of a single processor does not adversely affect the integrity of the data. The computer system can also overlay a switching system connected in a ring fashion for providing a fault tolerance to the failure of a single connected processor system at the switch level. Accordingly, there results a fault tolerant data distribution system.

Loosely coupled mass storage computer cluster

In a video on demand system utilizing asymmetric digital subscriber line (ADSL) interfaces, a plurality of video channels are arranged at a central office into ADSL format and, together with a provisioning channel, are multiplexed into a composite spectrum. This composite spectrum is then transmitted to an intermediate distribution point, remote from the central office, over analog optical fiber. The composite spectrum is split and applied individually to channel selection mixers associated with the subscribers serviced by the intermediate distribution point. Telephone signals (POTS) are combined at the intermediate distribution point into the ADSL signal and transmitted with the video, to an ADSL multiplexer/demultiplexer at the subscriber's location. In the reverse direction, channel direction/change signals are split from the composite received from the subscriber's location at the intermediate distribution point and utilized to control channel selection. Program request information is forwarded back over the optical fiber link to the central office where it is extracted at the ADSL individual channel units for use in providing video on demand service.

Extended range video on demand distribution system

An optical network has an optical splitter connected to (1) a working optical subscriber unit (OSU) of a working circuit, (2) a protection OSU of a protection circuit, and (3) one or more optical network terminals (ONTs), where an ONT has (i) a working line termination (LT) unit of the working circuit and connected to the optical splitter via a working optical fiber and (ii) a protection LT unit of the protection circuit and connected to the optical splitter via a protection optical fiber. The present invention enables fast protection switching from the working circuit to the protection circuit. The arrival times of corresponding downstream cells are measured at both the working and protection LT units of the ONT, and information related to the arrival times is transmitted from the ONT to the protection OSU. A propagation delay value is generated based on the transmitted information for use by the protection OSU for communications with the ONT if and when protection switching is implemented upon detection of a failure in the working circuit.

Fast protection switching by snooping on downstream signals in an optical network

Novel fibre optic telephone loop networks are disclosed. In the networks, single mode fibre optics are used for feeder and distribution segments of the loop but multimode fibre optics are used for the drops. The use of the multimode fibre optics has permitted the use of less costly optoelectronic devices. Surface light emitting diodes are such economical but reliable parts. Fibre service terminals located near subscriber premises convert single mode operation to the multimode operation. The networks are relatively easy to install and upgrade and are very economically competitive with other known FTTC and FTTH schemes. In a further embodiment, the fibre service terminals have microprocessor control to reroute signals via redundant single mode connections to central switching office in the event of a fault in single mode fibres.

Fibre optic telephone loop network.

For the receive-side clock supply for digital signals, such as digital data-compressed TV distribution signals, transmitted from a digital signal source, such as a TV signal source, via a connection unit and a light waveguide and/or coaxial line tree network connected thereto and respectively shared in common by a plurality of subscriber-side network termination units to the subscriber-side network termination units in the form of ATM signals, the required signal clock or clocks are separately transmitted at least proceeding from the connection unit to all network termination units connected to the light waveguide and/or coaxial line tree network. The digital signal acquired from the received ATM cells is thus time-regenerated thereat.

Method for receive-side clock supply for video signals digitally transmitted with ATM in fiber/coaxial subscriber line networks

A fiber optic telecommunication system has master site linked to a plurality of subscriber interface sites by a single pair of optical fibers. Downlink messages are transmitted in a continuous TDM format over a first optical fiber from the master site to subscriber interface sites, and in a burst mode TDMA format over a second optical fiber from the subscriber interface sites to the master site. Each subscriber interface site is coupled to the optical fiber link by way of a multiple fan-out fiber coupling pedestal at a common location on the fiber pair. To prevent collisions between successive uplink bursts from the subscriber interface sites, a guard band separates successive uplink messages from one another. The guard band duration accommodates optical fiber transmission distance between the common location on the uplink optical fiber and the subscriber interface site whose differential optical fiber transmission distance from the common location is greatest. A subscriber location has a television decoder associated with the subscriber's television set, through which television channel selection signals are input by the subscriber for transmission from the subscriber interface site to the master site. Power is provided by way of a replaceable battery pack, housed in a subterrestrial bell jar configuration, effectively insulating the battery pack from extreme temperature changes and the intrusion of moisture.

Fiber optic telecommunication system employing continuous downlink, burst uplink transmission format with preset uplink guard band

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Fiber optic telecommunication system employing continuous downlink, burst uplink transmission format with preset uplink guard band