FiberPlex WDM8 - Manual (Page 6)

Introduction
The FiberPlex WDM is an 8 or 16 Channel Wavelength Division Multiplexer, with each optical channel brought out to an SFP slot, so the user
does not need to supply wavelength‐specific modules. Each channel can be linked via fiber with selected FiberPlex FOM or FOI fiber modules,
FiberPlex LightViper™ or with virtually any third party fiber optic equipment with data rates from 155 megabits up to 3 gigabits per channel,
for a possible maximum aggregate data rate of 48 gigabits.
The user data enters and leaves the WDM via 16 SFP slots on the WDM16, or 8 slots on the WDM8A and WDM8B, which can be left
unpopulated for unused channels, or populated with user‐supplied MSA‐compliant SFP modules that are appropriate for the user’s data rate,
protocol and jitter requirements. Internally, these connect to fiber optic transceivers which are tuned to the specific wavelengths for the
channels, which are then multiplexed onto the aggregate pair which connect to the other WDM(s) in the link. Data that enters a specific
channel on one WDM will appear on the corresponding channel on the other WDM(s) in the link, with no interference with any other
channels.
Possible link configurations are:
 WDM16 to WDM16 – all 16 channels through
 WDM8A to WDM8A – all 8 channels through
 WDM8B to WDM8B – all 8 channels through
The aggregate fibers from the WDM units exit the chassis via a duplex LC coupler, which connect to single mode fiber, up to 20 km in length.
Since this is an aggregated wideband stream, any user equipment in the optical path (switches, couplers, etc.) must be able to accommodate
the entire bandwidth without attenuation, and will not be able to receive or decode the stream digitally.
The WDM units have provision for two (2) power supply modules for redundancy each having capacity to power the entire unit. An AC power
input module is available now and a DC version is in development; both are ‘hot swappable’.
Key Features
 16 (or 8) Channel Active Wave Division Multiplexer
 Combines 16 (or 8) optical channels into a single fiber pair
 Each channel independently supports data rates from 155 MB up to 3 GB
 SMPTE compatible internal fiber optics, video optimized to support Pathological Signals
 Each optic channel can independently accept multimode or single mode optics, coax connection or CAT5 using flexible SFP modules
 Fully redundant, hot swappable power for ultimate reliability
WDM Theory of Operation
Infrared light has a frequency of approximately 400 Terahertz (400,000 Gigahertz). That is about 125,000 times higher than the data rate of a
typical 3 Gigabit SFP, which means a large proportion of the bandwidth of a fiber optic cable is wasted. The current state of the art does not
allow utilizing all of that bandwidth, but we can recover some of it by a technique called “Coarse Wave Division Multiplexing,” or “CWDM.”
Essentially, it is the simple technique of taking each 3 Gigabit channel and using it to modulate a different frequency in that 400 Terahertz
bandwidth. This is done through a series of optical filters and combiners, along with lasers and photodiodes tuned to a particular infrared
center frequency. Historically, however, optics are referred to, not by their frequency, but by their wavelength, which is the speed of light
divided by the frequency.
In the traditional implementation of a CWDM, it is the user’s responsibility to provide the tailored SFPs and the CWDM itself, which may
require adapters to interface with the user equipment.
The Fiberplex WDM line, on the other hand, is an active WDM, with the wavelength‐specific components already tested and configured.
Instead of a wavelength‐specific optical fiber, a generic SFP electrical interface is provided for each channel. Any SFP that conforms to the
MSA can be inserted, even copper‐based SFPs like gigabit Ethernet, SDI, HDMI or MADI.
The internal SFPs have a full 3 Gigabit bandwidth, video‐optimized. Generic fiber SFPs have limitations in passing video signals, since they do
not maintain a constant DC level. The video‐optimized SFPs are constructed to better handle the shifting DC levels in video signals.