Local computer networks which communicate over copper conductors have been developed both to promote resource sharing and provide increased performance. Such networks typically operate at bandwidth-length ( Bw \circ L ) products up to a few MHz \circ km . In this paper we consider the use of fiber optics in such networks, and give a status report on a star-configured fiber optic network experiment called Fibernet which operates at a Bw \circ L product of \sim 100 MHz\circ km at a data rate of 150 Mbits/s and which in its final phases will connect up to 19 stations. We compare the merits and problems of linear, ring and several star configurations, and of active versus passive networks. The packet communication protocol is discussed and network efficiency is calculated as a function of the packet length, channel capacity and network propagation time. We describe the system performance of the present Fibernet experiment, which uses a 19-port transmissive star coupler, GaAIAs injection lasers and avalanche photodiodes, and incorporates bi-phase data encoding. Power distribution inhomogeneities, observed in the output of the transmissive star coupler's mixer rod, are explained geometric-optically.

Fibernet: Multimode Optical Fibers for Local Computer Networks

A fiber-optic distribution system is disclosed which distributes broadband signals received by a network termination circuit from a broadband communications network (B-ISDN or cable-television network) among a plurality of subscriber terminals. The network termination circuit (4) contains devices for separating a forward channel and a backward channel. It also includes electric-to-optical and optical-to-electric transducers (5,6). The distribution system contains a fiber-optic multi-port coupler (10) which is made by the fusion technique and interconnects a plurality of optical fibers (12, 13, 14). On the subscriber's side, each of these optical fibers forms the forward channel and the backward channel for one of the terminals (32). On the network side, one of these optical fibers (16) forms the forward channel for the broadband signals, and all other optical fibers (17, 18) are combined to form the narrow-band backward channel. They are connected to a common large-area photodiode (6). As the backward channel is a narrow-band channel, the fact that large-area photodiodes, such as PIN diodes, are relatively slow does not cause any bandwidth problems.

Fiber-optic distribution system for broadband signals

A 3 dB coupler was fabricated using two partially polished fibres which were in contact with each polished portion. The excess insertion loss and the directivity of this coupler are measured to be 0.36 dB and 47.0 dB, respectively.

Fabrication of low-loss 3 dB couplers with multimode optical fibres

We present a full-duplex bidirectional data transmission link using twisted lights multiplexing over 1.1-km orbital angular momentum (OAM) fiber. OAM+1 and OAM−1 modes carrying 20-Gbit/s quadrature phase-shift keying (QPSK) signals are employed in the downlink and uplink transmission experiments. The observed mode crosstalks are less than −15.2 dB, and the full-duplex crosstalks are less than −12.7 dB. The measured full-duplex optical signal-to-noise ratio (OSNR) penalties at a bit-error rate (BER) of 2 × 10−3 are ~2.4 dB in the downlink transmission and ~2.3 dB in the uplink transmission. The obtained results show favorable full-duplex twisted lights multiplexing data transmission performance in a km-scale OAM fiber link.

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Full-duplex bidirectional data transmission link using twisted lights multiplexing over 1.1-km orbital angular momentum fiber.

Efficient combining of optical power from three input optical fibers to a single trunk fiber is demonstrated using fibers of different core/cladding diameters in a biconical taper configuration. The combiners have insertion loss less than 1 dB and optical isolation greater than −50 dB.

Efficient power combiner for multiplexing multiple sources to single‐fiber optical systems

Full duplex transmission of television signals over a single optical fiber is demonstrated The transmission link uses directional couplers that possess high directivity and low insertion loss

Andrew U. Tenne-Sens

Papers

Full duplex transmission link over single-strand optical fiber.