Introduction

0.4 Applications: Optoelectronic Transmitter/Receiver

Signal transmission Long distance digital signal transmission starts with information such as an email that is sent from a personal computer

Electrical signal propagation The computer creates a digital electrical signal that propagates along a copper wire

Optoelectronic transmitter This signal is then converted into an optical signal in an optoelectronic transmitter.

Transmitter board The heart of the transmitter is the transmitter board, a rather small printed circuit board containing a laser driver and laser diode

Transmitter circuit The transmitter circuit contains an amplifier that provides the current to the laser diode

Laser diode-fiber coupling The laser diode is coupled to an optical fiber with a small lens as a single "pigtailed" component

Light emission into the fiber The light emerging from the laser diode in response to the applied current diverges as it leaves the laser diode and is focused into the optical fiber

Optical signal transmission The light then travels along the optical fiber guided by a small difference in refractive index between the central core and lower-index cladding

Long distance fiber link The loss of a fiber is extremely low, which enables transmission over large distances with a minimal number of repeaters

Optoelectronic receiver The optical signal is converted back to an electrical signal close to its final destination by an optoelectronic receiver

Receiver board The heart of the receiver is the receiver board, a rather small printed circuit board containing a photodiode and photodiode pre-amplifier

Fiber-photodiode coupling Inside the receiver the light is coupled from the incoming fiber to a high-speed photodiode

Receiver circuit The photodiode current is then amplified in the receiver circuit to the extend that it is compatible with other logic circuits

Receiver output The output from the receiver propagates along copper wire to its final destination

Signal arrival The receiving computer displays the information represented by the electrical signal