The document provides an overview of optical detectors, emphasizing their critical role in optical fiber communication by converting optical signals into electrical ones. It outlines performance and compatibility requirements, such as high sensitivity, low noise, and stability, while detailing various types of photodetectors, including photomultiplier tubes and semiconductor photodiodes. Additionally, it discusses the evolution from first to third generation photodetectors, highlighting advancements in wavelength sensitivity and materials used.

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/