Bell Telephone Laboratories

Bell Communications Research, Inc.

At&t Bell Laboratories

Stewart David Personick

John S Cook

Willis Martin Muska

Steven S Cheng

Jan Lipson

Charles Arthur Brackett

An optical distribution architecture is disclosed wherein wavelength stabilized continuous wavelength lasers are centrally positioned in tandem with star couplers to distributed laser power among a plurality of lightguide paths. The laser power apportioned to each such path may then be locally or remotely modulated thereby reducing the number of lasers required to equip a network. Advantageously, lightguide fibres are single mode and polarization maintaining.

Optical transmission

An optical transmission network for transmitting information between two locations is disclosed. The transmission network comprises a collection of individual two-way links with all optical sources at one end. At a first location, the outputs of at least two lasers, operating at first and second wavelengths respectively, are multiplexed together, the resulting optical power being divided between a plurality of single mode optical fiber transmission paths. Each optical transmission path may include a wavelength selective modulator for modulating information onto the first wavelength for transmission from the first location to the second location. At the second location, the wavelengths are separated and the information modulated onto the first wavelength is detected. The second wavelength may be modulated with information to be transmitted back to the first location. No dedicated laser is required at the second location.

Shared laser lightwave transmission systems

A transitionally encoded data signal, which has a DC component and a bipolar AC component, is detected in an asynchronous receiver which includes a filter 16 for separating the AC and DC components into separate circuit paths, an amplifier 22 in the AC path, a feed-forward network 28 in the DC path for establishing a pair of threshold levels V.sub.th+ and V.sub.th- for detecting the positive and negative bipolar pulses, respectively, a dual comparator 26 for comparing the output of the amplifier with each of said threshold levels and for generating an output pulse whenever the thresholds are exceeded, and a set-reset flip-flop 34 responsive to the output pulses for reconstructing the binary signal which was transitionally encoded at the transmitter. Use of the receiver in a fiber-optic lightwave system is specifically described.

Asynchronous data receiver

A directional optical waveguide coupler and power tap is disclosed for use with optical fibers or planar-form optical waveguides. Abutted to the end of a cladded optical transmission waveguide is a section of a second optical waveguide comprising a core surrounded by a cladding layer, the core having a smaller cross-sectional area than the core of the transmission waveguide. In the present arrangement, light energy propagating in the core of the second waveguide towards the transmission waveguide is coupled into the core of the transmission waveguide at the point of abuttment, whereas light energy propagating in the core of the transmission waveguide towards the second waveguide is coupled into both the core and cladding layer of the second waveguide at the point of abuttment. Means disposed along the second waveguide adjacent the point of abuttment couples out of the cladding layer the cladding modes transferred from the core-guided modes of the transmission waveguide for subsequent conversion into a representative electrical signal. A stripper-absorber means is also disposed along the second waveguide for removing spurious cladding modes propagating therebeneath towards both the coupling out means and the point of abuttment between the two waveguides.

Directional optical waveguide coupler and power tap arrangement

A bipolar electrical signal of the type transmitted in the T1 digital transmission system is converted into an optical binary signal having pulses and spaces by translating each positive digital '1' in the bipolar signal into two digital pulses, each negative digital 1 in the bipolar signal into two spaces, and the digital 0 in the binary signal into an optical pulse followed by a space. The nonpermitted code of a space followed by an optical pulse is utilized at the receiving location for instantaneous framing. As a result of this particular code conversion, the balanced property of the bipolar input signal is maintained in the optical signal thereby preventing an offset bias from developing at the receiving location in the photodetector. In addition, the bipolar information is maintained in transmission, thus making the optical system 'transparent' to bipolar signals.

Growing community of inventors

Middletown, NJ, United States of America

Stewart David Personick