Abstract: A Gires-Tournois etalon (GTE) (10) comprising an optical fiber (12) in which a primary chirped fiber Bragg grating (FBG) (16) is provided, an RF signal generator (20), a piezoelectric transducer (22), and a glass horn (24), for coupling an acoustic wave (26) into the fiber (12). The acoustic wave (26) causes a periodic compression within the fiber (12), which induces a low frequency periodic refractive index modulation within the grating section (14) of the fiber (12). This causes two side frequency components to be generated for each high-frequency component of the FBG (16). Two secondary grating are thus excited, having the same spectral bandwidth as the FBG (16), but a lower reflectivity and different central wavelengths. The free spectral range of the GTE (10) can be adjusted by varying the frequency of the acoustic wave (26). The reflectivity of the excited secondary gratings can be adjusted by adjusting the amplitude of the acoustic wave (26).

Abstract: A Gires-Tournois etalon (GTE) (10) comprising an optical fibre (12) in which a primary chirped fibre Bragg grating (FBG) (16) is provided, an RF signal generator (20), a piezoelectric transducer (22), and a glass horn (24), for coupling an acoustic wave (26) into the fibre (12). The acoustic wave (26) causes a periodic compression within the fibre (12), which induces a low frequency periodic refractive index modulation within the grating section (14) of the fibre (12). This causes two side frequency components to be generated for each high-frequency component of the FBG (16). Two secondary grating are thus excited, having the same spectral bandwidth as the FBG (16), but a lower reflectivity and different central wavelengths. The free spectral range of the GTE (10) can be adjusted by varying the frequency of the acoustic wave (26). The reflectivity of the excited secondary gratings can be adjusted by adjusting the amplitude of the acoustic wave (26).

Abstract: A first embodiment of the invention provides a Gires-Tournois etalon (DGTE) 20 comprising a cladding mode suppressed optical fibre 22, including an etalon section 24 in which a weakly reflective optical waveguide grating 26 and a strongly reflective optical waveguide grating 28 are provided. The two gratings 26, 28 are chirped fibre Bragg gratings (FBGs). The chirped FBGs 26, 28 are arranged to together define an etalon cavity. Another aspect of the invention provides a dispersion compensator 60 comprising two DGTEs 62, 64 according to the first embodiment of the invention. The DGTEs 62, 64 have a linearly varying dispersion over a selected optical bandwidth. The first DGTE 62 has a positive dispersion slope and the second DGTE 64 has a negative dispersion slope. The magnitudes of the dispersion slopes of the two DGTEs 62, 64 are substantially equal, so that the dispersion compensator 60 has a constant dispersion across the selected bandwidth.

Abstract: Apparatus (10) for interrogating an optical signal (not shown) propagating in an optical waveguide, such as an optical fiber, having an input section (12) and a second section (14) through which light entering from the input section (12) will subsequently propagate. The second section (14) includes a grating portion, such as a tilted chirped fiber Bragg grating (16). The grating (16) causes at least part of the optical signal to be coupled out of the optical fiber, through the fiber cladding. A photodetector (18) is provided generally alongside the grating (16). The photodetector (18) is arranged to collect and detect substantially all of the outcoupled optical signal. The relationship between the optical power outcoupled by the grating (16) and the wavelength of the optical signal is known, allowing a measurement of the outcoupled optical power to be used to determine the wavelength of the optical signal propagating through the grating (16).

Abstract: A first embodiment of the invention provides a Gires-Tournois etalon (DGTE) 20 comprising a cladding mode suppressed optical fibre 22, including an etalon section 24 in which a weakly reflective optical waveguide grating 26 and a strongly reflective optical waveguide grating 28 are provided. The two gratings 26, 28 are chirped fibre Bragg gratings (FBGs). The chirped FBGs 26, 28 are arranged to together define an etalon cavity. Another aspect of the invention provides a dispersion compensator 60 comprising two DGTEs 62, 64 according to the first embodiment of the invention The DGTEs 62, 64 have a linearly varying dispersion over a selected optical bandwidth. The first DGTE 62 has a positive dispersion slope and the second DGTE 64 has a negative dispersion slope. The magnitudes of the dispersion slopes of the two DGTEs 62, 64 are substantially equal, so that the dispersion compensator 60 has a constant dispersion across the selected bandwidth.

Abstract: Apparatus (10) for interrogating an optical signal (not shown) propagating in an optical waveguide, such as an optical fibre, having an input section (12) and a second section (14) through which light entering from the input section (12) will subsequently propagate. The second section (14) includes a grating portion, such as a tilted chirped fibre Bragg grating (16). The grating (16) causes at least part of the optical signal to be coupled out of the optical fibre, through the fibre cladding. A photodetector (18) is provided generally alongside the grating (16). The photodetector (18) is arranged to collect and detect substantially all of the outcoupled optical signal. The relationship between the optical power outcoupled by the grating (16) and the wavelength of the optical signal is known, allowing a measurement of the outcoupled optical power to be used to determine the wavelength of the optical signal propagating through the grating (16).