First, for your
information, we would like to explain the essential differences
between the two "Fiber- To-The-Workplace (FTTW)" concepts. As
an example we have described the 100 Mbps solutions here. 10
Mbps or Token Ring solutions are, of course, also available.
Fiber-to-the-Desk (FttD):
Here every terminal is connected to a port of the central switch
by means of a dedicated fiber-optic link. First we would like to
tell you about the disadvantages of a conventional Fiber-To-The-Desk
concept in order to then explain the Nexans idea for a Fiber-To-The-Desk
solution.
Fiber-to-the-Office (FttO):
With this ideal fiber-optic concept (on Page 5) an active fiber-optic
link to the central switch is required for each standard office.
By using Nexans fiber share/fiber switch systems at the workplace
this high-performance optical connection can be used in many different
ways. This means that up to four terminals, such as PCs, printers
and IP telephones, share one fiber-optic link and one central switch
port. This makes the Nexans Fiber-To-The-Office concept clearly
more economical.
Contents
 Fiber-to-the-Desk
(FttD) - conventional concept
Nexans
solutions:
Fiber-to-the-Desk
(FttD)
Fiber to-the
Office (FttO) ideal solution with workplace switch
Reliable
optical networks
Redundancy
concept for maximum network reliability
Voice-over-IP
over Fiber
|
|
Conventional
Fiber-To-The-Desk Concept
The following diagram shows the typical configuration of a Fiber-To-The-Desk
link which we would not recommend: At first glance the Fiber-To-The-Desk
Solution for the optical connection of Terminals to the central
switch, as illustrated on next Page, appears to be ideal because
every terminal has a dedicated fiber-optic link.
Conventional "Fiber-To-The-Desk" concept
But this must be contrasted with the following disadvantages:
Every terminal
needs its own optical port on the central switch. These ports are
very expensive!
An optical port
has to be "wasted" on the switch even for terminals with a low
data throughput (printers, IP telephones). This is uneconomical!
Different types
of optical interface cards must be integrated in the switch for
terminals with 10Mbps or 100Mbps because - due to the different
optical |
wavelengths - there is no autonegotiation
function with optical ports. This means twice as much service provisioning!
The port density
with the standard TP switch interface cards is almost twice as
high as with optical interface cards. This means twice as many
chassis, twice as many network management cards and twice as much
space required in the network closets.
Not all terminals,
such as notebooks or printers, can be equipped with optical interfaces.
This means it is necessary to make an extra investment in external
media converters at the workplace!
Optical connecting
leads direct to the PC are a potential source of errors when these
are not protected against dirt and mechanical impact. This is not
guaranteed, however, because many users have a habit of rearranging
their PC or desk and thus also re-plugging the glass fibers into
the connections. This means that faults caused by damaged or incorrectly
plugged (transmitter/ receiver mixed up) fiber-optic connectors
are inevitable.
The optical connection
(2) to the terminal as illustrated on Page 2 can not be monitored
because optical network cards do not have a remote fault function.
This is a safety risk!
If the optical
connection (1) fails this can be indicated by the switch management.
But what happens when the PC is switched off when it is time to
leave work? A failure is indicated then as well! It is thus not
possible to monitor the optical connections, irrespective of the
status of the connected terminal! |