Optical detectors, as the name implied, can detect the amount of light received. It is a device that converts light signals into electrical signals, which can then be amplified and processed.

1. Introduction to Optical
Detector
BHAGYASHRI THORAT
Electronics & Telecommunication
International Institute of Information Technology, I²IT
www.isquareit.edu.in

2. Introduction Optical Detector
 Essential component of optical fiber
communication
 Convert the received optical signal
into electrical signal then amplified
before further processing

3. Performance and compatibility
Requirements of Detector
 High sensitivity at operating
wavelengths
 High fidelity
 Large electrical response to the
received optical signal
 Short response time to obtain a
suitable bandwidth
 A minimum noise introduced by a
detector
 Stability of performance
characteristics

4. Performance and compatibility
Requirements of Detector
continued
 Small size
 Low bias voltages
 High reliability
 Low cost

5. Types of Photodetector
• Photomultiplier Tubes
• Vacuum photodiodes
• Bulky, and require
high operating voltage
External
Photoemission
Devices
• Semiconductor
photodiodes
• Provides gain & good
performance, low cost
Internal
Photoemission
Devices

6. Semiconductor Photodetector
 Made from semiconductor silicon,
germanium and increasing no. of III- V
alloys
 Useful for Optical Communication
System
 Internal photoemission process may
take place in both intrinsic and
extrinsic semiconductor
 Intrinsic absorption process is
preferred.

7. First Generation
Photodetector
 Semiconductor Photodetector
 High sensitivity over 0.8 to 0.9 µm
wavelength band with adequate speed
(hundreds of megahertz)
 Negligible shunt conductance
 Low dark current
 Long term stability
 Widely used in first generation system

8. Second Generation
Photodetector
 1.1 – 1.6 µm wavelength range
 Germanium and III-V alloy
Photodetector

9. Third Generation Photodetector
 1..55 µm wavelength
 InP and III-V alloy Photodetector

10. Photodiode Devices
 p-i-n Photodiode
 Avalanche Photodiode

11. References
 Optical Fiber Communication second
edition By John M. Senior

12. Thank-You
International Institute of Information
Technology (I²IT)
P-14, Rajiv Gandhi Infotech Park, MIDC
Phase – 1, Hinjawadi, Pune – 411057,
India
info@isquareit.edu.in
http://www.isquareit.edu.in/