This document discusses optical fiber detectors. It describes the basic types of optical fiber detectors including PN photodiodes, PIN photodiodes, and avalanche photodiodes. It explains how each detector works by absorbing photons and generating electron-hole pairs that produce a photocurrent. The document also discusses parameters that characterize detector performance such as responsivity, quantum efficiency, and detectivity. Finally, it outlines different types of fiber sensors including intrinsic sensors like microbend and flow sensors, and extrinsic sensors for applications like level detection, pressure sensing, temperature measurement, and velocity measurement.

1. OPTICAL FIBER DETECTOR NAME:- SANDEEP KUMAR CLASS:- B.TECH 4 th YEAR BRANCH:- ECE

2. CONTENTS PHASE AND POLARIZATION FIBER SENSORS INTRINSIC FIBER SENSORS EXTRINSIC FIBER SENSORS

3. INTRODUCTION IT IS PART OF OPTICAL FIBER RECEIVER IT CONVERTS OPTICAL SIGNAL INTO ELECTRICAL SIGNAL THE ELCTRON EXCITED FROM VALANCE BAND TO CONDUCTION BAND REQUIRED LOW BIAS VOLTAGE

4. PROCESS OF OPTICAL FIBER DETECTOR ABSORPTION: TRANSPORTAION OF CARRIER: GENERATION OF PHOTOCURRENT:

5. PARAMETERS OF OPTICAL FIBER DETECTOR Responsivity : Quantum Efficiency : Capacitance : Response Time : Long wavelength cutoff : Wavelength = hc/Eg noise equivalent power (NEP) : detectivity : Figure 1— C-V Curve

6. PRINCIPLE OF OPERATION When a photon strikes the diode, it excites an electron , creating a mobile electron and a positively charged hole. If absorption occurs in depletion region,or diffusion length ,carriers are swept from the junction by built-in field .photocurrent is accured

7. TYPES OF OPTICAL FIBER DETECTOR THE OPTICAL FIBER DETECTOR IS BASICALLY THREE TYPE :- P-N PHOTODIODE P-I-N PHOTODIODE AVALANCHE PHOTODIODE

8. (1) P-N PHOTODIODE IF INCIDENT PHOTONS HAVE E p = hf =≥ E g THEN ELECTRONS MOVE FROM VALACE BAND TO CONDUCTION BAND

9. (2) P-I-N PHOTODIODE it consists of a thick, lightly doped intrinsic layer sandwiched between thin p and n regions . The word intrinsic means “natural”, “un-doped”. positive-intrinsic-negative .

10. PIN Photodiode

11. THE PIN PHOTODIODE IS TWO TYPES (1) FRONT ILLUMINATION PD :- The light passes through the thin p region and generates electron-hole pairs in the thick intrinsic layer . (2) REAR-ILLUMINATION PD :- light enters the active region through a heavily doped n + layer. This layer is transparent to the incident light because its energy gap is larger than the energy of incident photons.

13. (3)AVALANCHE PHOTODIODE The free carriers created by absorbed photon . A collision of carriers with neutral atoms ,bound electrons break out of the valence shell. The secondary carrier accelerate and create new carriers. Require high-voltage

14. AVALANCHE PHOTODIODE PROCESSS Figure 4 — APD

15. PARAMETERS OF AVALANCH PHOTODIODE IMPACT IONISATION COEFFICIENT RESPONSE TIME THRESHOLD IONISATION ENERGY MULTIPLICATION FACTOR OR CURRENT GAIN RESPONSIVITY

16. TYPES OF SENSORS PHASE AND POLARIZATION FIBER SENSORS INTRINSIC SENSOR (1)OPTICAL MICROBENDING SENSOR (2)OPTICAL FLOW METER SENSOR

17. EXTRINSIC SENSOR (1)OPTICAL FIBER LEVEL DETECTOR (2)PHOTOELASTIC PRESSURE DETECTOR (3)FLUOROPTIC TEMPERATURE DETECTOR (4)OPTICAL FIBER LASER DOPPLER VELOCIMETER

18. PHASE FIBER SENSOR

19. POLARIZATION FIBER SENSOR

20. FIBER MICROBENDING INTIRINSIC SENSOR

21. INTRINSIC OPTICAL FIBER FLOW METER

22. EXTRINSIC FIBER OPTICAL FLUID LEVEL DETECTOR

23. PHOTO ELASTIC PRESSURE SENSOR

24. FLUOROOPTIC TEMPERATURE SENSOR

25. FIBER LASER DOPPLER VELOCIMETER

26. THANK YOU VERY MUCH