Abstract: A wavelength correction apparatus automatically corrects a deviation of a testing wavelength from a reference spectrum analyzer installed on-site. The apparatus is constructed of a reference light source 62 for outputting a reference light of a specific wavelength; a light input terminal 50 for inputting a testing light whose wavelength is to be measured and compensated; an optical switch 54 for receiving the testing light and the reference light so as to output one either the testing light or the reference light; a control section 60 for controlling the operations of the reference light source 62 and the optical switch 54; and an optical spectrum measuring device 58 for measuring optical spectra output from the optical switch 54 and for operating the control section 60 at a point in time specified by an operator. The in-situ wavelength correction device produce precise compensates for wavelength deviation so that a compact wave correction apparatus can be used on-site of optical communications stations.

Abstract: Light having a predetermined wavelength band as issued from a light-emitting diode is launched into a gas absorption cell which is filled with a gas having a plurality of absorption spectra. The light launched into the cell has a plurality of wavelengths absorbed by the gas. The absorption wavelengths are known and their values are preset in a memory in an optical spectrum analyzing section 58. The light passing through the cell is launched into the optical spectrum analyzing section 58, where it receives arithmetic operations to produce an optical spectrum. The optical spectrum analyzing section 58 has a CPU which compares a plurality of wavelengths having dominant absorption in the obtained optical spectrum with the preset reference wavelengths to compute the errors in wavelength measurement. The calibration value is determined on the basis of the average of these errors and the optical spectrum analyzer is accordingly calibrated in wavelength.

Abstract: A high-precision spectrum separation apparatus enables to generate an output beam having a specific wavelength from a multi-wavelength input beam. The input beam is focused on a diffraction grating through a focusing lens to generate a number of diffracted component beams, of which a diffracted component beam having a specific wavelength is directed to an output slit, resulting in an output beam having well-defined spectral properties. When the output beam is required to have a band of wavelengths, the fixed focal distance of the focusing lens is shorter than is required to generate well-defined output beam, resulting that the diffracted component beam cannot be focused precisely on the output slit. In such a case, a flat glass plate is introduced between the focusing lens and the output slit to adjust the focal-point of the focusing lens so that the diffracted component beams are focused precisely on the output slit. An output beam having well-defined spectral properties is thus produced from the apparatus.