OPTICAL FIBER OPTICAL FIBER DETECTORDETECTOR

NAME:- SANDEEP KUMARNAME:- SANDEEP KUMAR

CLASS:- B.TECH 4 th YEARCLASS:- B.TECH 4 th YEAR

BRANCH:- ECEBRANCH:- ECE

CONTENTSCONTENTS

PHASE AND POLARIZATION PHASE AND POLARIZATION FIBER SENSORSFIBER SENSORS

INTRINSIC FIBER SENSORSINTRINSIC FIBER SENSORS

EXTRINSIC FIBER SENSORSEXTRINSIC FIBER SENSORS

INTRODUCTIONINTRODUCTION IT IS PART OF OPTICAL FIBER IT IS PART OF OPTICAL FIBER

RECEIVERRECEIVERIT CONVERTS IT CONVERTS OPTICALOPTICAL SIGNAL SIGNAL

INTO INTO ELECTRICALELECTRICAL SIGNAL SIGNAL THE ELCTRON EXCITED FROM THE ELCTRON EXCITED FROM

VALANCE VALANCE BAND TO BAND TO CONDUCTIONCONDUCTION BAND BAND

REQUIRED LOW REQUIRED LOW BIAS VOLTAGEBIAS VOLTAGE

PROCESS OF OPTICAL PROCESS OF OPTICAL FIBER DETECTORFIBER DETECTOR

ABSORPTION: ABSORPTION: TRANSPORTAION OF TRANSPORTAION OF CARRIER: CARRIER:

GENERATION OF GENERATION OF PHOTOCURRENT:PHOTOCURRENT:

PARAMETERS OF OPTICAL PARAMETERS OF OPTICAL FIBER DETECTORFIBER DETECTOR

ResponsivityResponsivity: :

Quantum EfficiencyQuantum Efficiency::CapacitanceCapacitance: : Response TimeResponse Time::Long wavelength Long wavelength

cutoffcutoff:: Wavelength = hc/EgWavelength = hc/Eg

noise equivalent noise equivalent power (NEP)power (NEP) : :

detectivitydetectivity : :

Figure 1— C-V Curve

PRINCIPLE OF OPERATIONPRINCIPLE OF OPERATIONWhen a photon strikes the diode, it excites an electron, creating a mobile electron and a positively charged hole.

If absorption occurs indepletion region,or diffusion length ,carriers are swept from the junction by built-in field .photocurrent is accured

TYPES OF OPTICAL FIBER TYPES OF OPTICAL FIBER DETECTORDETECTOR

THE OPTICAL FIBER THE OPTICAL FIBER DETECTOR IS BASICALLY DETECTOR IS BASICALLY THREE TYPETHREE TYPE:-:-

(1)(1)P-N PHOTODIODEP-N PHOTODIODE

(2)(2)P-I-N PHOTODIODEP-I-N PHOTODIODE

(3)(3)AVALANCHE PHOTODIODEAVALANCHE PHOTODIODE

(1)(1) P-N PHOTODIODEP-N PHOTODIODEIF INCIDENT IF INCIDENT

PHOTONS HAVE PHOTONS HAVE EEp =p =hfhf=≥ =≥ EEgg

THEN THEN ELECTRONSELECTRONS

MOVE FROM MOVE FROM VALACE BAND VALACE BAND TOTO

CONDUCTION CONDUCTION BANDBAND

(2)(2) P-I-N PHOTODIODEP-I-N PHOTODIODE

it consists of a thick, it consists of a thick, lightly doped lightly doped intrinsic intrinsic layerlayer sandwiched between sandwiched between thin p and n regionsthin p and n regions..

The word intrinsic means The word intrinsic means “natural”, “un-doped”. “natural”, “un-doped”. positive-intrinsic-negativepositive-intrinsic-negative..

PIN Photodiode

THE PIN PHOTODIODE IS THE PIN PHOTODIODE IS TWO TYPESTWO TYPES

(1)(1) FRONT ILLUMINATION PD FRONT ILLUMINATION PD :-:-

The light passes through the thin The light passes through the thin pp regionregion and generates electron-hole and generates electron-hole pairs in the thick pairs in the thick intrinsic layerintrinsic layer. .

(2)(2) REAR-ILLUMINATION PDREAR-ILLUMINATION PD:-:-

light enters the active region light enters the active region through a heavily doped through a heavily doped nn++ layer.layer. This layer is transparent This layer is transparent to the incident light because its to the incident light because its energyenergy gap is largergap is larger than the than the energy of incident photons.energy of incident photons.

(3)AVALANCHE (3)AVALANCHE PHOTODIODEPHOTODIODE

The free The free carriers createdcarriers created by by absorbed photonabsorbed photon. .

A A collisioncollision of carriers with of carriers with

neutral atoms ,bound electronsneutral atoms ,bound electrons

break out of the valence shell. break out of the valence shell. The The secondary carriersecondary carrier accelerate accelerate and create new and create new carriers. carriers. Require high-voltageRequire high-voltage

AVALANCHE PHOTODIODE AVALANCHE PHOTODIODE PROCESSSPROCESSS

Figure 4 — APD

PARAMETERS OF PARAMETERS OF AVALANCH AVALANCH

PHOTODIODEPHOTODIODEIMPACT IONISATION IMPACT IONISATION

COEFFICIENTCOEFFICIENTRESPONSE TIMERESPONSE TIMETHRESHOLD IONISATION ENERGYTHRESHOLD IONISATION ENERGYMULTIPLICATION FACTOR OR MULTIPLICATION FACTOR OR

CURRENT GAINCURRENT GAINRESPONSIVITYRESPONSIVITY

TYPES OF SENSORSTYPES OF SENSORSPHASE AND PHASE AND POLARIZATION FIBER POLARIZATION FIBER SENSORSSENSORS

INTRINSIC SENSORINTRINSIC SENSOR (1)OPTICAL MICROBENDING(1)OPTICAL MICROBENDING

SENSOR SENSOR

(2)OPTICAL FLOW METER(2)OPTICAL FLOW METER

SENSORSENSOR

EXTRINSIC SENSOREXTRINSIC SENSOR(1)OPTICAL FIBER LEVEL (1)OPTICAL FIBER LEVEL

DETECTORDETECTOR

(2)PHOTOELASTIC PRESSURE (2)PHOTOELASTIC PRESSURE

DETECTORDETECTOR

(3)FLUOROPTIC TEMPERATURE(3)FLUOROPTIC TEMPERATURE

DETECTORDETECTOR

(4)OPTICAL FIBER LASER (4)OPTICAL FIBER LASER DOPPLER VELOCIMETERDOPPLER VELOCIMETER

PHASE FIBER SENSORPHASE FIBER SENSOR

POLARIZATION FIBER POLARIZATION FIBER SENSORSENSOR

FIBER MICROBENDING FIBER MICROBENDING INTIRINSIC SENSORINTIRINSIC SENSOR

INTRINSIC OPTICAL INTRINSIC OPTICAL FIBER FLOW METERFIBER FLOW METER

EXTRINSIC FIBER EXTRINSIC FIBER OPTICAL FLUID LEVEL OPTICAL FLUID LEVEL

DETECTORDETECTOR

PHOTO ELASTICPHOTO ELASTIC PRESSUREPRESSURE SENSORSENSOR

FLUOROOPTIC FLUOROOPTIC TEMPERATURE SENSORTEMPERATURE SENSOR

FIBER LASER DOPPLER FIBER LASER DOPPLER VELOCIMETER VELOCIMETER