SU1267278A1 - Acoustical-optical analyzer of spectra of pulse signals - Google Patents

Description

The invention relates to devices for optical signal processing and can be used to obtain a spectrum of pulse signals. The purpose of the invention is to increase the signal-to-noise ratio, to increase the laser power. The drawing shows the function of the acousto-optic spectrum analyzer of pulse signals. The device comprises a laser 1, the output of which is optically coupled to the collimator 2, optically connected also to the linear frequency modulating (chirp) diffraction grating 3, which is connected to the optical input of the multi-pass acousto-optic light modulator 4 (AMC), to an electric The cic input of which is supplied is a pulse source signal. The optical output of the AMC 4 is connected to the input of the integrating loop 5, and its outputs are optically connected to the photodetectors 8 and 9 through the trellis diaphragms 6 and 7, the inputs of the adder 10 are electrically connected to the outputs of the photodetectors 8 and 9; and its output is with the input of the serial spectrum analyzer 11, the retractor of which is the output of the device. thirty

The acousto-optical spectrum analyzer of pulsed signals works as follows.

The input pulse signal is supplied to the multi-input input. AMC 4, which is made as follows: on the upper edge a slice is made to install the piezoelectric transducer at an angle of 90 ° - © 6 and at a distance b pa tR06 (where is the number of acoustic wave moves in AMC, even number; O.- transverse size of AMC) also made a cut at an angle | L 180 ° - © 6 for the installation of the absorber. Thus, a sawtooth-shaped form of acoustic wave propagation with multiple reflections is provided: from the lower and upper edges of the AMC. The light beam from laser 1 is expanded by a collimator 2, then diffracts on the chirp lattice 3, forming reference beams corresponding to (-1) and (+1) th diffraction orders, as well as the non-diffracted component. A light beam corresponding to a component not diffracted on a grating passes through a multi-pass AMC in which an acoustic wave (spatial

waves in AMC), it is advisable to choose the resolution ability of the lattice diaphragms (where Afpa is the resolution of the frequency pc, of the regional spectrum analyzer).

Since Afpa is

that

dx (f / v) nfvr ,. where Fd is the frequency band;

t analysis time. The width of the slits d of the lattice diaphragms is advisable to choose so that d kP Jdfp / V Hgde. k 0.1-0.3), and with the parameters of the chirp diffraction grating

. so that Af, V Fa, f Kho V f, (where d, (and f) (are, respectively, the spatial frequency difference and the center frequency of the chirped diffraction grating,;. f is the center frequency of the AMC). The counters are converted by the photoreceivers 8 and 9 the sum of radio pulses that go to the corresponding inputs of the adder 10 and further to the serial spectrum analyzer 11, which forms the spectrum of the original pulse signal at its output.8 analog of the input signal propagates from the piezoelectric transducer at an angle with the optical axis of the system tp 90 ° +85, reflects Referring further from the bottom face at an angle to the system optical axis 270 ,, ° then similarly from the upper face, etc. and diffracts on each of the ultrasonic wave propagation segments, deviating in the direction of o; jHoro or another photodetector, respectively. Then, the integrating lens 5 performs spatial separation of the diffraction orders. In the first-order region, the trellis diaphragms 6 and 7 and the photodetectors 8 and 9 are installed, which record the counts of the interference pattern resulting from the interaction of the transformed lens 5 of the signal and chirp light beams. Lattice diaphragms located symmetrically: evenly with respect to the optical axis, are designed so that the distance between the holes JF / V (where Afp is the frequency resolution; Jv is the wavelength of light; F is the focal length of the integrating lens; V is the speed ultrasound propagation

The use of trellis diaphragms at the inputs of the photodetectors and the chirped diffraction grating, which serves as the generator of the reference beams, together with the multi-pass AMC, allows receiving the sum of radio pulses at the output of the photoreceivers, whose amplitudes are proportional to the amplitudes of the spectral components selected by the grating diaphragm. The duration of these pulses is approximately equal to the time spent by the spatial analog of the electric signal in the AMC aperture. An increase in the processing time due to repeated passage of the pulse under study in the AMS aperture allows the use of a narrowband frequency tunable filter, on the basis of which a sequential spectrum analyzer is based. Thus, the bandwidth of the post-detector processing path decreases from the signal band in the prototype to the resolution of the sequential spectral analyzer and, therefore, the signal-to-noise ratio increases by () times.

Claims (1)

Invention Formula Acousto-optic spectrum analyzer of pulse signals, containing located on the same opti-. . a laser axis, an optically coupled laser, a collimator, an acousto-optic light modulator, an integrating lens and a first photodetector installed in the focal plane of the integrating lens, in the region of one of the first diffraction orders in front of which is a diaphragm distinguished by the fact that in order to increase the signal-to-noise ratio without increasing the laser power, it contains a linear-frequency-modulating diffraction grating installed between the collimator and the acousto-optic light modulator, a second photodetector mounted in the focal plane of the integrating lens in the region of another diffraction order, This has a lattice diaphragm installed in front of each photodetector. .dh AG / UIFa / T,. where, L is the wavelength of light; F is the focal distance of the integrating lens; V - propagation velocity sound waves in the acousto-optic light modulator; Fd - frequency band; T - time analysis an adder, the inputs of which are connected to the outputs of the first and second photodetectors, respectively, and the output is connected to the input of a serial spectrum analyzer, the output of which is the output of the device, and the acousto-optical light modulator is made multi-way with piezoelectric transducers mounted on the modulator: at an angle (90 - © Bk optical. Axis (where 06 is the Bragg angle).