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Fiber Optics Photo Diode Module

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Fiber optics Photo diode module Trainer kit, has been uses for study the fiber optic systems. In this module have internal DC source and this module will be supporting external DC voltage also. This module designs for study the Optical Photo Diode voltage vs current (VI) characteristics in Forward Bias, Reverse Bias and Zero Bias. And this module uses for students to get knowledge about optical components.

Principle of Photo Diode

Photodiodes are frequently used photo detectors. They are semiconductor devices which contain a p–n junction, and often an intrinsic (undoped) layer between n and p layers. Devices with an intrinsic layer are called P-I-N or PIN photodiodes. Light absorbed in the depletion region or the intrinsic region generates electron–hole pairs, most of which contribute to a photocurrent. The photocurrent can be quite precisely proportional to the absorbed (or incident) light intensity over a wide range of optical powers.

Operation Modes

Photodiodes can be operated in two very different modes:

Photovoltaic mode: like a solar cell, the illuminated photodiode generates a voltage which can be measured. However, the dependence of this voltage on the light power is nonlinear, and the dynamic range is fairly small. Also, the maximum speed is not achieved.

Photoconductive mode: here, a reverse voltage is applied to the diode (i.e., a voltage in the direction where the diode is not conducting without incident light) and measures the resulting photocurrent. (It may also suffice to keep the applied voltage close to zero.) The dependence of the photocurrent on the light power can be very linear over six or more orders of magnitude of the light power, e.g. in a range from a few nanowatts to tens of milliwatts for a silicon p–i–n photodiode with an active area of a few mm2. The magnitude of the reverse voltage has nearly no influence on the photocurrent and only a weak influence on the (typically small) dark current (obtained without light), but a higher voltage tends to make the response faster and also increases the heating of the device.

Forward Bias Operation

Reverse Bias Operation

Zero Bias Operation

Optical fiber

The transmission medium in fiber-optic communications systems is an optical fiber. The optical fiber is the transparent flexible filament that guides light from a transmitter to a receiver. An optical information signal entered at the transmitter end of a fiber – optic communications system is delivered to the receiver end by the optical fiber.

Model Diagram for Plastic Fiber cable


Fiber cable Properties

fiber cable properties



☞ Photo Diode Type : PIN Photo Diode

☞ Source Wavelength : 660nm to 950 nm

☞ Supply Voltage : +12V DC

☞ Internal DC Source : 0V to +5V

☞ External DC Input : 0V to +5V (Below +5V only)

☞ Photo Diode operation mode : Forward Bias, Reverse Bias and Zero Bias

☞ Photo Diode Interface : Self locking Cap

☞ Supply current : 100 mA (Maximum)

☞ Fiber Cable Type : 1000 Micron Plastic Fiber Cable

☞ Core Refractive Index : 1.492

☞ Cladding Refractive Index : 1.406

☞ Interface connectors : 2mm socket


☞On-board DC source.

☞Input over voltage protection using active components.

☞Supporting External DC voltage at variable range (0V to +5V).

☞Number of test point to study the Photo Diode characteristics.

☞Wider bandwidth link at 660nm to 950 nm.

Internal DC Source

In this module internal DC source produce variable DC voltage at the range of 0V to +5V.

External DC Input

This module was design to supporting external DC voltage at variable range .Here we will give DC voltage in the range of below +5V.

Photo Diode

Here we were used Optical Photo Diode SFH 250V and study this diode characteristics.


In this module will need +12V/500mA DC adapter for power supply. That will be converting +5V in on board.

Front Panel Diagram for Photo Diode Module




Experiment 1:

To Study the VI Characteristics of Photo Diode at Forward Bias

Experiment 2:

To Study the VI Characteristics of Photo Diode at Reverse Bias

Experiment 3:

To Study the Characteristics of Photo Diode at Zero Bias

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