Optical spectrum analyser

Fig. 1. Schematic diagram of the present wave tank experiment OSA = second Optical Spectrum Analyser MOSA = Multichannel ("Stroboscopic") Optical Spectrum Analyser...

The Multichannel ("Stroboscopic") Optical Spectrum Analyser (MOSA) allows us to carry out spatial Fourier analysis of the images of a ruffled water surface. One can show (see, Appendix) that the frequency spectrum s(co) = < i cof > (<...> denotes statistical averaging) of the MOSA signal i t) can be written in the form... 

Monolight, Optical Spectrum Analyser, Rees Instruments, Ltd. (1992). 

In a silica fibre there are three transmission wavelength windows in which the losses are very low, such as 0.15dB/km at 1550 run. According to Eq. (9.23), typical values for the sensitivity to an applied axial strain in these windows are 1.2 nm/milli-strain at 1550 nm, 1 nm/milli-strain at 1300 run, and 0.66 nm/miUi-strain at 850 nm. The resolutions of FBG are 8.3 micro-strain at 1550 nm, 9.8 micro-strain at 1300 nm and 15 micro-strain at 850 mn by an optical spectrum analyser with a wavelength resolution of 10 pm. 

Any pulse can be described both in the time domain and in the frequency domain. In the time domain a signal may be oscillatory. The time domain behaviour is what is seen on an oscilloscope screen, because an oscilloscope is essentially an instrument for displaying a signal as a function of time. But a varying signal may also be described in terms of the components of each frequency present. This is a frequency domain description and is what is displayed by a spectrum analyser, just as an optical spectrum indicates the amount of each frequency (or wavelength) in a source of light. These two descriptions are related by a Fourier transform (Bracewell 1978), which may be written... 

TiN has an X 2S+ ground state and rotational transitions in the v = 0 level have been measured and analysed [69, 70] pure millimetre wave and microwave/optical double resonance methods were used, over a frequency range from 37 to 446 GHz. 14N hyperfrne structure was observed for the two lowest rotational transitions, and the spectrum analysed using the conventional effective Hamiltonian, again expressed in cartesian form ... 

Figure 9.14. Brillouin spectrometer using fibre optics to increase the signal-to-noise ratio. (1) Light source consisting of a master laser (1a) a slave with matched frequency (1b) and control unit (1c) for sensitive stabilization of the difference frequency Sv. (2) Signal splitter. (3) Fibre coupler. (4) Polarizer. (5) Chopper. (6) Lens. (7) Cuvette placed on a goniometer. (8) Termination. (9) Slit. (10) Broad-band (10 GHz) APD. (11) Photodiode with a smaller bandwidth (1 GHz). (12) Spectrum analyser (10 GHz) for controlling the intermediate frequency Sv. (13) Spectrum analyser (1 GHz) for the measurement of the half-power bandwidth, Av, of the Brillouin peak. (14) Amplifier system. (15) Process control computer. (Reproduced with permission of Elsevier, Ref [96].)...

Sample handling and preparation is very easy, as in the case of IR spectroscopy. Commercial instruments belong to two main types, conventional scanning and optical multichannel analysers. The main difference between both types is that, in scanning spectrometers, the scattered light is collected and analysed, usually at 1 cm intervals (channels), whereas in optical multichannel analysers a 300-600 cm section of the Raman spectrum, projected on to the detector, is rapidly recorded in a computer memory without... 

IROE-FLIDAR-2 was used (3). The system consisted of a laser source producing a pulse every second with a wavelength of 480 nm and a duration of 15 ns a telescope which collected the radiation from the canopy and an optical multichannel analyser (OMA) which analysed the collected radiation from the canopy at wavelengths over 540 nm to form a spectrum. The... 

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