Terms
Encapsulation type
Encapsulation types of optical modules include SFP, eSFP, SFP+, QSFP+, XFP, as
described in
Table 4-1
Encapsulation types of optical modules
Encapsulation
Type
Description
SFP
Small form-factor pluggable.
eSFP
Enhanced small form-factor pluggable. An eSFP module is an
SFP module that supports monitoring of voltage, temperature,
bias current, transmit optical power, and receive optical
power. Sometimes, eSFP is called SFP.
SFP+
Small form-factor pluggable plus, which is SFP with a higher
rate. SFP+ modules are more sensitive to electromagnetic
interference (EMI) because of their higher rate. To reduce
EMI, SFP+ modules have more springs than SFP modules and
the cages for SFP+ modules on a card are tighter.
QSFP+
Quad SFP+, four-channel SFP+.
XFP
10-GB small form-factor pluggable transceiver, 10GE optical
module. X is the Roman numeral 10, indicating 10G. All XFP
modules are 10G optical modules.
Transmission distance
Maximum distance over which optical signals can transmit. Optical signals sent from
different types of sources can transmit over different distances due to negative effects of
optical fibers, such as dispersion and attenuation.
Interface rate
Maximum rate of electrical signals that an optical device can transmit without bit errors.
Various interface rates are defined in Ethernet standards, such as 125 Mbit/s, 1.25 Gbit/
s, 10.3125 Gbit/s, and 41.25 Gbit/s.
Center wavelength
Wavelength measured at the midpoint of the half-amplitude line in the transmit spectrum.
Fiber mode
Mode of fibers defining based on core diameters and features of optical fibers. Optical
fibers are classified into single-mode fibers and multi-mode fibers. Generally, multi-
mode fibers have large core diameters and severe dispersion, so they transmit optical
signals over short distances when working with multi-mode optical modules. Single-
mode fibers have small dispersion and can transmit optical signals over long distances
when working with single-mode optical modules.
Modal bandwidth
Bandwidth measured at a point with transmit power several dB lower than that of the
point with the peak center wavelength. Modal bandwidth reflects spectrum
characteristics of an optical module.
S2750 Series Ethernet Switches
Hardware Description
4 Optical Module
Issue 04 (2014-03-20)
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