Northern Telecom Limited

Nortel Networks Corporation

John C Goodwin

John C Anderson

Frederick D King

Tibor F Devenyi

Keith Y K Lee

Geoffrey N Bowling

In an amplified wavelength division multiplexes (WDM) fiber optic communication system, each channel experiences a different optical gain, dispersion and noise. Also, the evolution of WDM fiber optic systems to higher density channel spacing has further aggravated multi-channel non-linear distortions such as four-wave mixing (FWM) and cross-phase modulation (XPM). The standard method for controlling these nonlinearities is the peak power control method. The performance of the channels can be equalized by adjusting the transmission powers of the optical transmitters. However, just equalization of a performance indication factor (PIF) such as BER or Q is not the optimum approach when peak power control mode of operation dominates. This invention is directed towards improving the margins of performance of WDM fiber optic channels. The transmission powers of the channels are adjusted methodically until the received performance margins of the channels are substantially equal then the power levels of the channels under peak power control mode are increased to just touch the provisional power level.

Over-equalization for multi-span wavelength division multiplexed fiber optic communication systems

A method and apparatus for transmitting an analog signal over an optical fiber cable is disclosed. A semiconductor laser provides an optical carrier signal, the laser having the natural linewidth at high power of the same order as the SBS linewidth. The method comprises directly modulating the current of the laser with a dither signal comprising a first component f.sub.C and a second component f.sub.S. Due to the nonlinearity of the 'I-V' characteristic of the laser, a thermal modulation component f.sub.T appears in the active region. This thermal modulation component reshapes the spectrum of the semiconductor laser to increase the threshold of the SBS. As a result, the energy of the signal transmitted over the optical cable may be increased by approximately 16 dB. The first frequency is at least twice the maximum frequency of the analog signal and the second frequency is selected to obtain f.sub.C -f.sub.S =f.sub.T.

Thermal down-mixing in diode laser transmitters to suppress stimulated

In methods and assemblies for packaging opto-electronic devices and for coupling optical fibers to the packaged devices, a housing has a cavity for receiving an opto-electronic device and an opening into the cavity. A window is placed across the opening to seal the opto-electronic device in the cavity. The window comprises a plurality of substantially parallel optical fiber sections joined side-by-side. An alignment and retention arrangement is mechanically coupled to the housing and is operable to align an optical fiber to the opto-electronic device through the window and to retain the optical fiber in that alignment. The methods and assemblies are particularly applicable to cost reduced packaging of opto-electronic devices for communications applications.

Methods and assemblies for packaging opto-electronic devices and for

A power and communication system for a building, and particularly a residential dwelling wherein there are provided a plurality of receptacles throughout the building, each connected by a cable to source, which may provide different voltages and either AC or DC and having a control interface for selectively switching the desired power to each cable individually. The control interface may also connect each cable to a selected signal transmission line, such as telephone, radio, TV, etc. The cable includes a pair of power conductors and a optical fiber which transmits to and receives from the control interface light signals informing the control interface what power or communication connection is required for a particular receptacle and possibly at the same time providing signal messages to each receptacle. The single optical cable can transmit an interrogating signal to the receptacle, which signal is transferred through a special plug and socket connection have a mating optical coupler to an appliance equipped with a microprocessor programmed for replying by way of light signals sent back to the interface through the same coupler and optical fiber. The control interface is thus informed as to what power and communication connections the appliance requires and to how the appliance should be subsequently monitored.

Closed loop, programmable power and communication system

A fiber optic switch of the moving fiber type and a method of making such switches. The switch has at least one stationary fiber and a mobile fiber carried by an actuator, preferably a bimorph, the end of the movable fiber being movable between a transmitting position in which the core of the mobile fiber is aligned with the core of the one stationary fiber and a position in which there is no alignment of the core of the mobile fiber with the core of the same stationary fiber. The stationary fiber is affixed to a smooth substrate surface with a slight flex downwardly between the point at which it is affixed to substrate surface and the end of the fiber which engages the substrate surface. The actuator is mounted to move in a plane substantially parallel to and above the substrate surface, and the mobile fiber is affixed to the actuator and with a downward flex between the point at which it is affixed to the actuator and the very end thereof which engages the substrate surface. The mobile fiber thus slides over the substrate on movement of the actuator. The flexed engagement of both fibers with the smooth substrate accomplishes accurate alignment of the cores of the fibers in the vertical direction, and the production of the switch with the fibers flexed as described above does not require the provision of any highly machined components.

Fiber optic switch

An optical switch has a reciprocating prism. In one position of the prism, light passes from an input fiber, through a collimating lens, directly to a focussing lens and then into an output fiber. In another prism position, the collimated light is incident on the prism, is deflected by the prism and enters a different focussing lens and output fiber. Coaxially aligned with the lenses are respective precision molded conical recesses which flare outwardly to receive the precision ground conical ends of fiber terminations.

Fiber optic switch with prism mounted for reciprocal and rotational

A device for making a splice between optical fibers, has a hollow cylindrical elastomer member within a housing. The elastomer member seats in a V-groove and a screw is driven against the elastomer member to deform the member and so grip and render coaxial a pair of fibers having ends meeting within the elastomer member. Jacketed portions of the two fibers are clamped on each side of the junction zone.

Optical fiber mechanical splice

To position a light output device such as a laser diode relative to a light device such as a waveguide so as to obtain maximum coupling of light, the waveguide end facing the laser is vibrated by mechanical means to modulate the coupled light. Light is detected from a remote end of the fiber and a corresponding electrical signal is generated. Positional information contained in the oscillatory component of the signal is decoded and applied to a positioning device which then reduces misalignment between the waveguide and laser. The positioning device continuously seeks the maximum coupling position. The technique finds particular application in positioning a waveguide in a laser package prior to and during anchoring.

Laser-fiber positioner

To position a light output device such as a laser diode relative to a light input device such as a waveguide so as to obtain maximum coupling of light, light is launched into one end of the fiber and is detected at a remote part of the fiber where a corresponding electrical signal is generated. Positional information contained in the signal is used to reduce misalignment between the waveguide and laser by manipulating a positioner attached to the fiber. Since there is usually some slight movement of the fiber as an anchoring epoxy bead cures, it is necessary to move the fiber within the curing epoxy and it is advantageous if the position at which the positioner contacts the fiber is at the same site as the epoxy bead. By the invention, the positioner is attached to the fiber using a wax or similar material so that as the epoxy cures, it does not cure in contact with the positioner. When the epoxy is fully cured, the wax is melted and the positioner withdrawn.

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Nepean, Canada

John C Goodwin