Abstract:
A laser drive circuit (700) compensates for laser diode (110) dynamics. A compensation value is determined from a sum of weighted basis functions. The basis functions may be a function of current desired optical powers and/or past desired optical powers. The weights may be updated periodically based at least in part on accumulated basis function outputs and measured optical powers.
Abstract:
A fiber amplifier uses an erbium-doped fiber core (1) in which a plurality of long-period fiber gratings (21) functioning as a gain equalizer are formed by an ultraviolet laser. Each of the fiber gratings (21) is irradiated with ultraviolet laser through the cladding layer of the optical fiber core (1) to provide periodic modulation for the refractive index of the fiber core. The fiber gratings (21) in the core (1) compensate for the wavelength dependency of gain to provide flat gain, resulting in uniform and efficient amplification over a wide range.
Abstract:
Techniques for controlling the shape of the gain spectrum of an optical amplifier (13) based on the temperature and level of inversion of the amplifier's amplifying medium (20) are provided. An increase in temperature for an amplifying medium having a high level of inversion results in an increase in gain for longer wavelengths relative to shorter wavelengths, i.e., a counterclockwise tilt of the gain spectrum, while an increase in temperature for an amplifying medium having a lower level of inversion results in the opposite effect, i.e., a clockwise tilt. These effects can be used to compensate for changes in the operating conditions of the amplifier, e.g., to compensate for changes in signal powers. The effects of thermal tuning are especially useful in WDM systems employing multi-stage amplifiers.
Abstract:
An optical amplifier having a series of optical fibers to which a rare earth element is added comprises one or more variable light-attenuating means and attenuation control means for varying the light attenuation of the variable light-attenuating means according to the temperature of the optical fibers or of the environment. An optical amplifier, in another aspect, having a series of optical fibers to which a rare earth element is added comprises a replaceable optical part, one or more variable light-attenuating means, and attenuation control means for varying the light attenuation of the variable light-attenuating means according to the temperature of the optical fibers or of the environment. An optical amplifier, in further another aspect, having a series of optical fibers to which a rare earth element is added comprises one or more externally-controllable variable light-attenuating means the light attenuation by which is changed with the intensities of the input and output signal lights of the optical amplifier.
Abstract:
A device with an optical fibre amplifier in which theres is a regulating circuit to stabilise the amplification. An additional optical signal (z) is applied to the input of the optical fibre amplifier within its optical amplification bandwidth in the regulating circuit. Its level is controlled by a control unit (Q) to the first input of which is applied a first measuring signal (m1) representing the level of an optical signal from a first region of the amplification bandwidth amplified by the optical fibre amplifier (V). At the second input of the control unit there is a second measuring signal (m2) representing the level of a so far unamplified optical signal from a second range of the amplification bandwidth.
Abstract:
In a gain-controlled erbium-doped optical amplifier, gain control is achieved by clamping the gain of a laser cavity to be equal to the overall cavity loss and by fixing the resonant wavelength of the amplifier to be at a first wavelength. When an optical signal to be amplified having a second wavelength different from the first wavelength passes through the amplifier the gain experienced by the signal depends entirely on the gain of the cavity, and not on the intensity of the signal. If the first wavelength is arranged to be at the peak of the sum of the absorption and emission cross sections of erbium, the amplifier exhibits minimum sensitivity to ambient changes in temperature.