Electrical to Optical Transducer | Optical to Electrical Transducer
This page compares Electrical to Optical Transducer versus Optical to Electrical Transducer and mentions difference between Electrical to Optical Transducer and Optical to Electrical Transducer types.
As we know there are many benefits of fiber optic system such as large bandwidth to carry high speed data, immunity against EM interference, light weight, low loss etc. Due to this, it is used to carry large bandwidth data across sea links, between exchanges and to connect two buildings in the vicinity of microwave antennas.
In order to transmit data which is in electrical format over fiber optic cable, it needs to be converted to optical form. To perform this function, electrical to optical transducer is needed at the transmit end. To recover the data in its original format, the optical format data needs to be converted to electrical form back. To perform this function, optical to electrical transducer is needed at the receive end.
Electrical to Optical Transducer
The common transducer devices used for electrical to optical conversion are as follows.
These are used at transmitter end of the fiber optic system.
• LED-Light Emitting Diode: It is inexpensive and reliable. They are used for lower bandwidth.
• LD-Laser Diode: They have very narrow spectrum. They are used for higher bandwidth.
Following are the features of LED.
• It is made from compound called gallium arsenide phosphide.
• It converts electrical signal to optical signal in infrared wavelength of about 850 nm. PCM signals are converted to infrared pulses.
• They are used for low data rate transmission systems with speeds of 30 Mbps.
• The figure-2 mentions typical circuit symbol of LED with anode and cathode terminals.
Following are the features of Laser Diode.
• Made of gallium arsenide phosphide.
• Power output is about 10mWatt.
• It has faster ON/OFF switching speed compare to LED.
• It has narrower spectral width (10-5 to 5 nm).
• It has very high modulation bandwidth in the order of tens of MHz to tens of GHz.
Refer LED versus Laser diode>>.
Optical to Electrical Transducer
The common transducer devices used for optical to electrical conversion are as follows.
These are used at receiver end of the fiber optic system.
• PIN Diode: Operates well at low bandwidth.
• Avalance Diode: Operates at higher data rate.
The different materials produce light in different wavelengths. The common materials include silicon (190 to 1100) , germanium (400 to 1700), InGaAs (800 to 2600) , Lead Sulfide (<1000 to 3500) etc.
Following are the features of PIN Diode.
• The optical light is absorbed when photons of any wavelength fall on PIN diode and converted to electrical energy.
• The figure-4 depicts P-I-N diode schematic with I-layer (Intrinsic) between P and N materials. I-layer has small amount of dopent with wide depletion region.
• It has reverse bias voltage of 3 volts.
Following are the features of Avalanche Diode.
• It does amplification of the signal in addition to optical detection.
• Avalanche diode consists of n+, p, π and p+ regions in its structure.
• When photons of light falls, it gets absorbed in the π region and results into generation of electron-hole pairs. This way optical signal is converted to electrical signal.
• Avalanche Diode is PIN diode with very high reverse bias voltage.
• It has reverse bias voltage of 50 volts.
Refer PIN diode versus Avalanche diode>>.
Sensors and Transducers Related Links
Refer following links to know more on types of sensors and transducers:
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