An adaptive equalizer to compensate for the effects of frequency-selective fading on a microwave radio system. The equalizer includes two Bode-type bump networks and an AGC amplifier whose slope and gain are respectively controlled by pilot tones added to the message load. Importantly, the frequency characteristics of the two Bode networks are non-overlapping, thus ensuring stability.

Defective repeaters in a multihop, digital microwave transmission system are located by the use of a special test pattern which is generated at the transmitting terminal. At each repeater station, the two outputs of the phase demodulator are compared to determine if the test pattern has been properly received from the upstream repeaters. The special test pattern, S, has the characteristic that S = S(2N); that is to say, the test pattern equals the complement of itself delayed by 2N symbols. This...

An optical cable which is relatively immune to the effects of bending and/or tension comprises a helical optical fiber loosely confined within a protective sheath. Apparatus is disclosed for fabricating the helical fiber. For example, as the fiber is drawn from a heated preform the fiber is subjected to periodic, pulsating jets of an inert gas, such as nitrogen, which physically deform the fiber into the desired helical configuration.

Apparatus for interconnecting a time-division multiplex carrier system, such as T1, with a frequency-division multiplex carrier system, such as LMX-3. The interconnexion is effected in an all digital manner by the use of digital filters, thus avoiding the necessity of down-converting either system to voiceband.

A feedbackward, distortion-compensating circuit suitable for pre- and post-distortion compensation of non-linear amplifying devices. The circuit taps-off a portion of the output signal of the compensating circuit, cubes it, and combines it with the input signal to that circuit. Appropriate adjustments to the phase and amplitude of the cubed signal ensure that the output signal of the non-linear amplifying device is free from all significant distortion.

Intelligible crosstalk in microwave radio systems employing single-sideband modulation is substantially eliminated by phase-modulating the AM carrier-wave prior to its modulation by the baseband signal. The phase-modulation may comprise a periodic signal, such as a single sinusoidal tone or pseudo-random noise, or it may comprise an aperiodic signal such as a truly random noise. In this latter event, the coding signal is transmitted to the receiving location to ensure proper demodulation of the ...

A process for manufacturing preforms from which clad optical fibers having longitudinal, eccentric, azimuthal index inhomogeneities may be drawn. In one embodiment, the known CVD process for making preforms is modified by the use of asymmetric heating to produce circumferentially alternating deposits of doped and undoped glass which act as the fiber core when the preform is subsequently collapsed and drawn into a fiber.

Alternate lines of a 526 line video signal are time-stretched and transmitted over a transmission channel of limited bandwidth. At the receiver, the lines are compressed back to their original duration and displayed in an interlaced manner on a conventional receiver by blanking alternate lines in each field. In another embodiment of the invention, adjacent transmitted lines of the video signal are averaged at the receiver and the resultant signals are substituted for the non-transmitted lines of...

In a digital transmission system of the type which employs cross-polarized radio channels, the failure of a transmitter associated with a particular channel can cause an undesired signal cross-over into the receiver of the failed channel. According to the instant invention, each channel in the system is uniquely encoded by a combination of bitstream inversion and bitstream delay at the head end of the system. Thus, if a signal crossover occurs an excessive number of parity violations are detecte...

In a chemical vapor deposition (CVD) process for manufacturing a fiber optic preform, a glass rod is inserted into the preform during the deposition of the core layer. This yields a fiber having a longitudinal eccentric index inhomogeneity which is close to the axis of the fiber.