Nortel Networks Corporation

Northern Telecom Limited

Corning Incorporated

Fiona Davis

Nigel Edward Jolley

Richard E Epworth

Michael John Yadlowsky

Kevin Wallace Bennett

Kim Byron Roberts

Mark A Newhouse

Robert William Keys

Richard A Habel

Paul Anthony Jakobson

A variable gain optical amplifier, in which homogeneous gain broadening is dominant, has first and second fixed gain rare-earth doped optical waveguide amplifiers () optically in series together with an intervening variable attenuation optical attenuator (). This arrangement circumvents the problem of gain tilt encountered when operating such amplifiers under variable gain conditions. An alternative form of the module has variable gain waveguide amplifiers, but these are co-regulated so that the aggregate of their gain at a wavelength within the gain spectrum is maintained constant. A further alternative form of module is employed in a concatenation of such modules. In such a concatenation, the gain of individual modules is allowed to vary, but the aggregate of the gain, at a wavelength within the gain spectrum, of all the waveguide amplifiers of all the modules of the concatenation is maintained constant.

Optical amplifier modules

A variable gain optical amplifier, in which homogeneous gain broadening is dominant, has first and second fixed gain rare-earth doped optical waveguide amplifiers ( ) optically in series together with an intervening variable attenuation optical attenuator ( ). This arrangement circumvents the problem of gain tilt encountered when operating such amplifiers under variable gain conditions. An alternative form of the module has variable gain waveguide amplifiers, but these are co-regulated so that the aggregate of their gain at a wavelength within the gain spectrum is maintained constant. A further alternative form of module is employed in a concatenation of such modules. In such a concatenation, the gain of individual modules is allowed to vary, but the aggregate of the gain, at wavelength within the gain spectrum, of all the waveguide amplifiers of all the modules of the concatenation is maintained constant.

Multistage optical amplifier with gain flattening

The variables and parameters previously understood to affect the gain spectrum of an optical amplifier 13 were: (1) the wavelengths to be amplified; (2) the input power levels at those wavelengths; (3) the characteristics of the amplifying medium 20; (4) the insertion loss spectra of the amplifier's components, including any filter(s) used for gain flattening; (5) the pump band chosen to pump the amplifying medium 20; and (6) the total amount of pump power supplied in the chosen pump band. An additional fundamental variable has been identified which can be used to control the gain spectrum of an optical amplifier 13, namely, the center wavelength of the spectrum of the pump's output power within the chosen pump band. Methods and apparatus for using this variable for this purpose are disclosed. For example a, transmission system is disclosed having a transmitter 11 and a receiver 10 connected by an optical fiber 12. A plurality of optical amplifiers 13 are located along the optical fiber 12 to amplify signal channels between the transmitter and receiver. Each of the amplifiers has a pump light source 21, the wavelength of which is such that contributions to differential gain due to pump light wavelength related effects is substantially reduced. Also disclosed is a WDM transmission system having a transmission path including a concatenation of laser diode pumped optical amplifiers 13 wherein the gain spectrum of an amplifier is controlled at least in part by a feedback loop regulating the temperature of its laser diode pump 21. The feedback loop may for instance derive its control signal from a measure of the drive current applied to the pump, of the emission wavelength of the pump, or of the disparity between the power output from the amplifier in one of the multiplexed signal channels and that from at least one other of the channels.

Pump wavelength tuning of optical amplifiers and use of same in

An optically amplifying waveguide guides both the LP.sub.01 and the LP.sub.02 mode. Its erbium distribution profile is preferentially matched with the modal field distribution of the LP.sub.02 mode. The waveguide is provided with long period perturbations of a pitch and strength that resonantly couples signal power of different wavelengths from propagation in the LP.sub.01 mode to propagation in the LP.sub.02 mode and back again to propagation in the LP.sub.01 mode whereby the longitudinal distribution of gain along the waveguide at one wavelength is longitudinally displaced with respect to that at least one other wavelength.

Optically pumped optical waveguide amplifier

Growing community of inventors

Bishops Stortford, United Kingdom

Fiona Davis