Arrangement for monitoring the emission wavelength and power of an optical source

An arrangement for monitoring the main radiation beam emitted by an optical source such as a laser diode ( 10 ) having a nominal emission wavelength, includes first ( 18 ) and second ( 20 ) photodetectors as well as a wavelength selective element ( 22 ). A beam splitter module ( 16 ) is provided for splitting a secondary beam from the main radiation beam of the laser source and directing it towards the first ( 18 ) photodetector via the associated wavelength selective element ( 22 ). The wavelength selective element ( 22 ) has a wavelength selective transmittance-reflectance characteristic, whereby said secondary beam is partly propagated towards said first ( 18 ) photodetector and partly reflected from said wavelength selective element ( 22 ) towards the second ( 20 ) photodetector. The output signals ( 18 a, 20 a) from the photodiodes ( 18, 20 ) have intensities whose behaviours as a function of wavelength are complementary to each other. Signal processing circuitry ( 32 ) is further provided including an adder module ( 26 ) and subtractor module ( 28 ) fed with the output signals from the photodiodes 818, 20 ) to generate: a wavelength-independent sum signal ( 26 a; ?A1+?B1), indicative of the intensity of the optical radiation generated by the optical source ( 10 ), and a wavelength-dependent difference signal ( 28 a; ?′A1−?′B1), indicative of the difference between the actual wavelength of the radiation generated by said optical source ( 10 ) and its nominal emission wavelength.