Abstract: There is provided a tunable external-cavity laser and a tunable laser source based on such tunable external-cavity laser. The tunable external-cavity laser comprises: two reflective surfaces to form a laser cavity therebetween; an active waveguide for amplifying laser light propagating in the laser cavity; a tunable wavelength-selective filter within the laser cavity for selecting the emission wavelength of the tunable external-cavity laser with in a tuning range; and a collimating lens system for collimating the optical beam out of the active waveguide for propagation in the laser cavity. The collimating lens system comprises an imaging lens and a collimating lens for collimating the optical beam. The imaging lens induces a positive chromatism within the tuning range and the collimating lens comprises a complex lens inducing a negative chromatism within the tuning range so as to at least partially compensate for the positive chromatism induced by the imaging lens.

Abstract: There is proposed an optical power measurement circuit and an optical power meter which use a linear amplification circuit based on multiple transimpedance operational amplification lanes and which add a bootstrap circuit and a compensator circuit. 1) The bootstrap is used to reduce the effect of the photodiode capacitance and increases the amplifier's bandwidth. 2) The compensator circuit monitors the photodiode's voltage and reproduces its transient distortions, to then subtract it from the output and thereby reduce the measurement error.

Abstract: There is provided a method for measuring the PDL of a DUT as a function of the optical frequency ? within a spectral range, which uses a single wavelength scan over which the input-SOP varies in a continuous manner. The power transmission through the DUT, curve T(?), is measured during the scan and the PDL is derived from the sideband components of the power transmission curve T(?) that results from the continuously varying input-SOP. More specifically, the Discrete Fourier Transform (DFT) of the power transmission curve T(?) is calculated, wherein the DFT shows at least two sidebands. At least two sidebands are extracted and their inverse DFT calculated individually to obtain complex transmissions (?), =?J . . . J, where J is the number of sidebands on one side.