T1/E1 lines can be leased from TELCOs and can support data transmission
at a rate of 1.544 MBPS. As applications require greater and
greater transmission speeds there has been increasing use of
T1 leased lines in corporate networks. However, TELCO responsibility
for the line and its performance begins and ends at the wall
of the building. The question then arises as to how you take
T1/E1 to/from the line to the actual data equipment communicating
e.g. the LAN Router or the PBX. A TELCO will do this for you,
but at some not insignificant expense. An alternate possibility
is to link the T1 line to the data equipment by fiber optic
Along the same lines, increasingly high rate premises data
communication devices such as Routers and Ethernet Switches
are being ordered
with T1 interfaces. This allows the traffic from them to go
directly to Wide Area Networks (WANs) by way of a leased T1
line. A commonly used alternative
is to connect these devices together with fiber optic cables
and using the 78X connect the two WANs together.
Carrying out data communications using fiber optic cables in
the premises environment presents several ready advantages.
First, there is tremendous bandwidth potential. Not only can
it deal with the T1 traffic it can handle much greater rates,
easily, over premises distances. Applications which require
very high data transmission rates can be easily accommodated.
Secondly, there is the protection that fiber optic transmission
provides against the variety of deleterious effects which plague
transmission over copper cable. These include the resistance
that fiber optic transmission has to Electromagnetic Interference
(EMI), lightning induced current surges and ground loops. Finally,
there is the protection that fiber optic transmission has with
respect to 'tapping.' It is much more secure with no effective
radiation of the communication occurring out of the cable.
In order to link traffic derived from a T1/E1 leased (copper)
line to your data equipment you will need a T1/E1 Fiber Optic
Modem. The Model 78X modems are ideal for this purpose as stand
alone units. If you need versions appropriate for a card cage
then the Model 278X modems can be employed. The 'X' denotes
operating mode/wavelength/connector options. Respectively, these
are: multi-mode/single-mode, 850nm/1300nm and ST/FC.
The employment of the Model 78X in a typical application is
shown in the illustration above. On the left hand side and right
hand side of the illustration are Routers. Each may be receiving
traffic from a separate leased T1 line and want to forward it
to a LAN station associated with the other Router. Each Router
has a T1 interface. The Routers can be linked by employing a
pair of Model 78Xs with fiber optic cable. As you can see, the
distance that this Router-to-Router link can cover is quite
large if the right mode option is chosen-up to 29 km.