At&t Bell Laboratories

At+t Corp.

At&t Company

Yan-Chi Shi

Nils A Olsson

Mohamed M Mekawi

Leon Klafter

Edward E Harstead

A multiple-access network communication system employs a single continuous-wave optical carrier which is successively modulated and multiplexed at a plurality of data access nodes. The data access nodes are cascaded along an optical propagation path, and at each such node, the optical carrier is impressed with an modulated electrical signal which corresponds to an electrical subcarrier having a subcarrier frequency which is uniquely responsive to its associated data access node. Local data at each such node is modulated electrically in accordance with a known modulation scheme, such as FSK modulation, the resulting modulated subcarrier being conducted to a respective optical modulator which impresses same upon the optical carrier. The optical carrier is periodically, with respect to the data access nodes, amplified by an optical amplifier, and ultimately conducted to a receiver where the optical carrier is detected and converted to a corresponding electrical signal. The electrical signal is then demultiplexed, illustratively by filters tuned to the subcarrier frequencies, each of which is then demodulated, whereby the original data signal is recovered. The invention can be implemented in bidirectional embodiments which permit modulated optical carrier to be propagated in opposite directions. In addition, a bidirectional embodiment can be provided with both optical carriers from a single laser source.

Optical successive modulation-muliplexing for fiber optical network

An optical rotary joint has a first pair of light beam expanding graded index (GRIN) of refraction lenses coupled to ends of a first pair of lightguide fibers for coupling signals through the rotary joint interface in a first path which is coaxial with the axis of rotation in the interface. A second pair of lightguide fibers are coupled to a second pair of GRIN lenses off-axis and of much smaller diameter than the lenses of the first pair. Prisms couple signals between the off-axis lenses and a second path across the interface and which is also coaxial with the axis of rotation. Also shown is a method for compensating for lens irregularities.

Plural-channel optical rotary joint

A laser-driven interferometric signal sensing system has a cleaved-coupled cavity laser with separate stabilization servo loops of different time constants for the modulator and laser sections thereof. The laser section is biased above lasing threshold, and its stabilization loop is operated at a frequency twice the frequency of laser section bias current modulation. A laser loop feedback error signal is a function of predetermined, environmental-type, parameter variations in the sensing location and is processed to be a function of the second derivative of interferometer output intensity with respect to laser section current. That error signal is applied to modify laser section bias current in a direction to zero out the feedback signal.

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Parsippany, NJ, United States of America

Yan-Chi Shi