Nortel Networks Corporation

Bookham Technology Limited

Christopher R Fludger

Richard E Epworth

Kim Bryon Roberts

Han Henry Sun

Leo L Strawczynski

Maurice M O'Sullivan

Alan Robinson

Jonathan Paul King

James E Whiteaway

Kevin J Cordina

Nigel Edward Jolley

Andrew V Maroney

Peter Jeremy Anslow

Jowan Masum-Thomas

Adrien Comeau

Richard Thomas

Dave Walker

A method of synthesizing a modulated optical signal using a laser cascaded with an amplitude modulator. A phase drive signal V(t) is derived for driving the laser to generate an optical carrier signal with a desired phase &#x3c6;(t). An amplitude drive signal V(t) is then derived for driving the amplitude modulator to impose a desired amplitude S(t) onto the optical carrier signal generated by the laser. The amplitude drive signal V(t) is compensated for amplitude modulation of the optical carrier signal generated by the laser.

Optical E-field modulation using a directly driven laser

Use in an optical communications system of multiple detectors to separately detect respective multiple spectral modes of a received optical signal. The invention also provides for corresponding multi-channel, dispersion-tolerant optical receivers. Embodiments are presented both for direct detection and for coherent detection of optical signals.

Multi-detector detection of optical signals

A polarization diversity receiver has an optical section for converting the received optical signal into four or five polarization diverse component optical signals that substantially represent amplitude and polarization state information of the received optical signal, by respective polarization transformations to respective points on a Poincar&#xe9; sphere, the points being equally spaced apart to maximize polarization diversity, even in the worst case input polarization state. Detectors produce component electrical signals from each of the component optical signals, for electronic processing to compensate for PMD. By reducing the number of component optical signals significant cost and size reductions are enabled. The need for precise polarization tracking in the receiver can be reduced or eliminated completely. Balanced detectors can be used to reduce the number of electrical signals. The electrical processing can use sequence detection.

Polarization diversity receiver for optical transmission system

An optical transmission system comprising a first optical waveguide suitable for transmitting a first information signal, a second optical waveguide suitable for transmitting a second information signal, and input means for providing an electro magnetic radiation signal into said first waveguide, said signal being suitable for providing Raman amplification of the information signals, the system further comprising an optical coupling between said waveguides, arranged to transmit at least a portion of the Raman amplification signal from the first waveguide to the second whilst substantially blocking the transmission of the information signals between the waveguides.

Raman amplification

In a first aspect, a Raman amplifier is pumped using pumps just above and below the fiber water peak. This enables lower power pumps to be used, as the high attenuation is avoided. In a second aspect, a first pump provides a signal having a first wavelength and a first power, and a second pump source provides a plurality of signals, each having a power lower than the first power and a wavelength in a range approximately one Stokes shift higher than the first wavelength. In this way, the second pump source signals are amplified by the Raman effect by the first pump source signal, and the amplified second pump source signals cause signal amplification. The amplified second pump source signals can then include wavelengths above and below the water peak.

An optical fiber amplifier or laser comprises an optical housing having a diffusive reflective inner surface and at least one opening for receiving pump light. An optical fiber having a doped core is at least partially contained within the optical housing. The optical fiber can be pumped by an optical source without the need for any complex or expensive optical couplers. Lateral illumination of the fiber core with pump light enables many fibers to be pumped by the same pump source, so that a separate dedicated coupler is no longer required to couple the pump light into each optical cable.

Optical fiber device

Growing community of inventors

Cambridge, United Kingdom

Christopher R Fludger