Current optical spectrum analysis devices use bulk optic diffraction gratings as an optical tuning element. Light exiting from an optical fibre is focused onto the diffraction grating, and the light reflected by the diffraction grating is focused in turn onto an optical detector.

Such devices have several disadvantages. Diffraction gratings are subject to mechanical shock and damage, so such devices have limited ruggedness and tolerance of mechanical vibration; mechanical movement of the diffraction gratings leads to limited accuracy and resolution; the position of the diffraction grating is likely to drift with time and may be affected by mechanical backlash; and the light must be extracted from the optical fibre for measurement, requiring accurate focusing of the light onto the diffraction grating and the optical detector.

Such devices therefore have limited performance, require regular calibration, are expensive, and generally unsuitable for in-the-field monitoring of optical systems.

Researchers at Aston University have invented an optical spectrum analyzer that overcomes these difficulties. The device comprises a tuneable optical filter fabricated from optical fibre with inscribed fibre Bragg gratings, through which an optical signal is passed. The use of fibre Bragg gratings rather than bulk optics significantly increases ruggedness, eliminates intolerance of vibration, increases accuracy and resolution, and drastically lowers costs.