Introduction

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.

Fiber diameter Diameter of the core of a fiber. According to international standards for optical fibers,
the diameter of a multi-mode fiber is 62.5 um or 50 um, and the diameter of a single-
mode fiber is 9 um.
Fiber class Optical signals with different wavelengths have their best working windows in different
optical fibers. To help efficiently adjust wavelengths or dispersion features of optical
fibers and change their refractive indexes, the following classes are defined: multi-mode
fiber (G.651), common single-mode fiber (G.652), shifted dispersion fiber (G.653), and
non-zero shifted dispersion fiber (G.655). G.651 and G.652 are commonly used fiber
classes.
Connector type Type of the interface on an optical module to accommodate a fiber. Commonly used
connector types are LC (applicable to all the SFP, SFP+, and XFP modules), MPO
(applicable to some of QSFP+ modules), and SC.
Transmit optical power Output optical power of an optical module when it is working properly.
Maximum receiver  Minimum average input optical power that the receiver of an optical module can receive
sensitivity   within a range of bit error rate (BER = 10 -12 )
Overload optical power Maximum average input optical power that the receiver of an optical module can receive
within a range of bit error rate (BER = 10 -12 ).
Extinction ratio Minimum ratio of the average optical power with signals transmitted against the average
optical power without signals transmitted in complete modulation mode. The extinction
ratio indicates the capability of an optical module to identify signal 0 and signal 1.

Appearance

Feature

NOTE.

The appearance of CWDM and DWDM optical modules is similar to that of common optical modules.
These optical modules are distinguished by their labels. In practice, the corresponding optical fibers are
labeled to distinguish the optical modules.