24-12-2012, 12:05 PM
VOICE TRANSMISSION THROUGH LASER
VOICE TRANSMISSION.pptx (Size: 468.18 KB / Downloads: 44)
Our project is the voice transmission through LASER. The voice signal is converted into electrical signal using microphone and after that signal is amplified by Op-Amp using as inverting amplifier after that the signal is further amplified using push-pull amplifier & then the signal is converted into optical signal using LASER diode.
The optical signal is picked up by photo diode which converts it into electrical signal and this is amplified using Op-Amp and push-pull amplifier. The amplified electrical signal is applied to the loud-speaker to generate original voice signal.
Transmitter
The audio or voice signal which is to sent our or through laser link is given to microphone. The microphone works as a transducer & converts audio / voice signal into an electrical signal
The electrical signal is now filtered by an 1000µf electrolytic capacitor.
The electrical signal is now given to the operational amplifier. The op-amp here is used as the inverting amplifier. By using this configuration of op-amp this reduces the amount of noise injected into the amplifier by the input signal, because any noise appears simultaneously on both input terminal and the amplifying circuitry rejects it being a common mode signal i.e the electrical signal is amplified with the rejection of noise.
Now the signal is given to complementary symmetry push-pull class B power amplifier. The signal applied at the input goes to the base of both transistors. The two transistors conduct in opposite half cycles of the input. Eg. During +ve half cycle of i/p signal NPN transistor is forward biased and conducts while the PNP transistor is reverse biased and vice-versa. So, now the electrical signal is amplified by the push pull amplifier. The amplified output signal is given to the zener diode which maintains a constant 3.6v across the LASER diode. The electrical signal is now converted into optical signal by LASER diode i.e information signal is converted into optical signal which is sent by the LASER to the receiver side.
Reciever section:-
The light or optical signal or information signal is now picked up by the photo diode which converts light signal into its equivalent electrical signal i.e it works as a transducer which can convert light signal into electrical signal. The electrical signal is now filtered by an 1000µf electrolytic capacitor. The signal is now given to the operational amplifier.
The op-amp here is used as the inverting amplifier. By using this configuration of op-amp this reduces the amount of noise injected into the amplifier by the input signal, because any noise appears simultaneously on both input terminal and the amplifying circuitry rejects it being a common mode signal i.e the electrical signal is amplified with the rejection of noise.
Now the signal is given to complementary symmetery push-pull class B power amplifier. The signal applied at the input goes to the base of both transistors. The two transistors conduct in opposite half cycles of the input. Eg. During +ve half cycle of i/p signal NPN transistor is forward biased and conducts while the PNP transistor is reverse biased and vice-versa. So, now the electrical signal is amplified by the push pull amplifier. The amplified signal is now filtered by an 470µf capacitor.
The filtered electrical signal is applied to the loud speaker. Which converts electrical signal into the audio signal i.e we get the original sound signal at the loud speaker. So, the voice is transmitted through LASER by this circuit
Communication technology:-
Communication technology has experienced a continual development to higher and higher carrier frequencies, starting from a few hundred kilohertz at Marconi's time to several hundred terahertz since we employ lasers in fiber systems. The main driving force was that the usable bandwidth - and hence transmission capacity - increases proportional to the carrier frequency. Another asset comes into play in free-space point-to-point links. The minimum divergence obtainable with a freely propagating beam of electromagnetic waves scales proportional to the wavelength. The jump from microwaves to light waves therefore means a reduction in beamwidth by orders of magnitude, even if we use transmit antennas of much smaller diameter. The reduced beam width does not only imply increased intensity at the receiver site but also reduced cross talk between closely operating links and less chance for eavesdropping.
For the past quarter century, wireless communication has been hailed as the superior method for transmitting video, audio, data and various analog signals. Laser offers many well-known advantages over twisted pair and coaxial cable, including immunity to electrical interference and superior bandwidth. For these and many other reasons, wireless transmission systems have been increasingly integrated into a wide range of applications across many industries.