1. What is a Optical Transceiver?
Optical Transceivers are typically used to create high bandwidth links between network switches.
GBIC, SFP, XENPAK, X2 and XFP are all form factors of Optical Transceiver providing up to 10
Gbps data throughput. With Optical Transceiver you can also create data transmission links
capable of long range transmission.
Optical Transceivers include both a transmitter and a receiver in the same component. These are
arranged in parallel so that they can operate independently of each other. Both the receiver and
the transmitter have their own circuitry so that they can handle transmissions in both directions.
Optical Transceivers typically interface with two common types of fiber optic cables, single mode
and multimode. Single mode is an optical fiber that will allow only one mode to propagate. The
fiber has a very small core diameter of approximately 8 μm. It permits signal transmission at
extremely high bandwidth and allows very long transmission distances.
Multimode fiber optic cable supports the propagation of multiple transmission modes
(wavelengths). Multi mode fiber typically has a core diameter of 50 to 100 μm with a refractive
index that is graded or stepped. It allows the use of inexpensive LED light sources and connector
alignment and coupling is less critical than single mode fiber. Distances of transmission and
transmission bandwidth are less than with single mode fiber due to dispersion.
Some fiber optic transceivers can be used for both single mode and multimode cables. Common
connector types for Optical Transceivers include Biconic, D4, ESCON, FC, FDDI, LC, Loopback,
MTP, MT-RJ, MU, SC, SMA, and ST. General performance specifications to consider include
wavelength, operating voltage, data rate, and bandwidth.
Important receiver performance parameters to consider when searching for Optical Transceivers
include sensitivity, responsivity, and receiver rise time. The sensitivity specifies the weakest
optical signal that can be received. The minimum signal that can be received depends on the noise
floor of the transceiver module module front end. The measure of responsivity is the ratio of
radiant energy expressed in watts (W) incident on the device, to the resulting photocurrent
expressed in amperes (A). It is represented as an absolute sensitivity expressed by A/W. In the
approximation of a step function, the receiver rise time is the time required for a signal to change
from a specified 10% to 90% of full power.
Rise time is a way of expressing the speed of the receiver. Important transmitter performance
specifications to consider include light source, spectral width, and maximum optical output power
and transmitter rise time. The light source can be LED or laser diode. Light Emitting Diodes
(LEDs) have relatively large emitting areas and as a result are not as good light sources as Laser
diodes. However, they are widely used for short to moderate transmission distances because they
are much more economical. Laser Diodes (LDs) can couple many times more power to optical
fiber than LEDs. They are primarily used for applications that require the transmission of signals
over long distances. In the approximation of a step function, the transmitter rise time is the time
required for a signal to change from a specified 10% to 90% of full power. Rise time is a way of
expressing the speed of the transmitter.
2. Common features for fiber optic transceivers include clock recovery, pigtail, stand alone, and
signal input and output choices. An important environmental parameter to consider is the
operating temperature.
Major optical transceiver brand:
Major brands like Cisco transceiver, HP transceiver, 3Com transceiver, Finisar
transceiver ， Juniper transceiver, Foundry transceiver, Extreme transceiver, Netgear transceiver,
Force10 transceiver, Brocade transceiver, Dell transceiver, Enterasys transceiver and etc.
