Abstract: A Bragg grating has a local reflection strength which varies with position along the length of the grating so as to generate a non-uniform wavelength reflection spectrum, enabling compensation for a non-uniform gain profile of the gain section of a tunable laser. In another aspect, a Bragg comb grating is modulated by an envelope function which can also compensate for a non-uniform gain profile. The comb grating may be a phase change grating, with the envelope function shape being controlled by the length between phase changes and/or size of the phase changes.

Abstract: A cascaded optical amplifier including a first optical amplifier and a second optical amplifier in cascaded arrangement is provided. Each of the first optical amplifier and the second optical amplifier has a respective input for receiving an optical signal, an output for outputting an amplified optical signal, and a control input for controlling the gain of the optical amplifier. The cascaded optical amplifier includes a sensor for sensing upstream of the input of the second optical amplier a signal relating to operation of the cascaded optical amplifier. In addition, the cascaded optical amplifier includes a controller for providing control signals to the respective control inputs of the first amplifier and the second amplifier, the controller providing the control signal to the second optical amplifier as a function of the sensed signal.

Abstract: A tunable laser comprises a gain section and two or more reflectors. At least one of the reflectors is a Bragg grating comprising a reduced strength section comprising a base order periodic pattern of marks and spaces from at which at least some of the marks or spaces are missing. This enables the reflective strength of the grating to be controlled relative to the other reflector. The Bragg grating may be a phase change grating with individual sections being reduced in strength by line removal.

Abstract: An optical analyzer (14) for performing spectral analysis on an optical beam (18) includes an optical filter (28), a mover (30), an optical launcher (36), and an optical receiver (38). The optical filter (28) includes a filter area (46) that is a narrow band pass type filter having multiple alternative center bandwidths that are distributed along the filter area (46). The mover (30) moves the optical filter (28). The first optical launcher (36) directs the optical beam (18) at the filter area (46) so that the optical beam (18) is near normal incidence to the filter area (46). The optical analyzer (14) can be used to simultaneously monitor multiple optical signals. Additionally, the optical analyzer (14) can include a beam redirector (40) that causes the optical beam (18) to make two passes through the optical filter (28).

Abstract: A Bragg grating has a local reflection strength which varies with position along the length of the grating so as to generate a non-uniform wavelength reflection spectrum, enabling compensation for a non-uniform gain profile of the gain section of a tunable laser. In another aspect, a Bragg comb grating is modulated by an envelope function which can also compensate for a non-uniform gain profile. The comb grating may be a phase change grating, with the envelope function shape being controlled by the length between phase changes and/or size of the phase changes.