Diffraction grating monochromator

A method for calibrating a monochromator apparatus, comprising:

• receiving an optical signal;
• detecting a 0th order diffracted signal and an angle of the 0th order diffracted signal, wherein the 0th order diffracted signal is obtained by diffracting the optical signal on a diffraction grating;
• setting the angle of the 0th order diffracted signal as a reference angle;
• detecting a next order diffracted signal and another angle of the next order diffracted signal;
• and
• determining a wavelength of the next order diffracted signal based on the reference angle and the another angle of the next order diffracted signal.

An optical spectrum analyzer (OSA), comprising:

• a diffraction grating comprising a plurality of diffractive elements, the diffraction grating to receive an optical signal having a plurality of wavelengths and to transmit a plurality of diffracted signals;
• an detection component to detect one or more of the plurality of diffracted signals from the diffraction grating;
• and
• a processor communicatively coupled to the diffraction grating and the detection component, the processor, in a calibration process, to:
• receive a rotational angle of the diffraction grating for a 0th order diffracted signal and set the rotational angle as a reference angle;
• receive a detected next order diffracted signal and another rotational angle of the diffraction grating for the next order diffracted signal;
• and
• determine a wavelength of the next order diffracted signal based on the reference angle and the another rotational angle of the diffraction grating for the next order diffracted signal.