User Manual
ADCP-75-110 • Issue B • March 2001
Page 20
©
2001,
ADC
Telecommunications,
Inc.
2.4 Optical Options and Requirements
Each
DHU
and
its
associated
DEUs
and
DRUs
are
connected
over
a
pair
of
fiber
optic
links.
One
link
transports
the
forward
path
optical
signal
and
the
other
link
transports
the
reverse
path
optical
signal.
Either
50
or
62.5
micron
core
multi-mode
fiber
optic
cable
may
be
used
for
the
optical
link.
If
50
micron
cable
is
used,
the
optical
link
may
be
up
to
750
meters
(2,460.75
ft)
in
length.
If
62.5
micron
cable
is
used,
the
optical
link
may
be
up
to
500
meters
(1,640.5
ft)
in
length.
Whenever
possible,
use
conduit
or
a
guideway
such
as
the
FiberGuide
system
to
route
the
optical
links
between
the
DHU,
the
DEUs,
and
the
DRUs.
Avoid
routing
optical
fibers
through
ladder
type
cable
racks
or
troughs
that
do
not
provide
sufficient
support
to
limit
bending
or
prevent
accidental
damage.
Tie-wrapping
is
not
recommended
as
a
means
of
securing
fiber
optic
cables.
Provide
sufficient
slack
at
each
unit
for
connecting
each
fiber
to
the
required
port.
Fibers
may
be
pre-
terminated
or
terminated
on-site
using
field-installable
LC
type
connectors.
2.5 Coaxial Cable Requirements
The
DHU
interfaces
either
locally
(see
Figure
8)
or
remotely
(see
Figure
9)
with
the
BTS
through
coaxial
cable
connections.
In
a
local
interface
with
the
BTS,
coaxial
cables
are
required
to
link
the
DHU
with
the
LIU
and
the
LIU
with
the
BTS.
In
a
remote
interface,
coaxial
cables
are
required
to
link
the
DHU
with
the
RIU
and
the
RIU
with
the
donor
antenna.
The
DHU,
LIU,
and
RIU
are
equipped
with
N-type
female
connectors
for
connecting
the
forward
and
reverse
path
coaxial
cables.
Use
high
performance,
flexible,
low
loss
50-ohm
coaxial
communications
cable
(RG
400
or
equivalent)
for
all
connections.
2.6 System Expansion Planning
The
DEU
enables
6-way
expansion
of
any
optical
port.
This
makes
is
possible
to
add
more
DRUs
without
having
to
install
additional
DHUs.
Each
DHU
is
equipped
with
six
optical
ports.
If
more
than
six
DRUs
are
required
by
the
application,
a
DEU
may
be
connected
to
one
of
the
optical
ports
at
the
DHU
which
expands
that
port
to
six
ports.
If
still
more
optical
ports
are
required,
then
a
second
DEU
may
be
connected
to
the
DHU
or
a
second
DEU
may
be
connected
to
the
first
DEU.
The
ability
to
cascade
DEU’s
in
parallel
or
in
series
provides
unlimited
flexibility.
It
is
physically
possible
to
connect
an
unlimited
number
DRUs
to
the
DHU
through
the
installation
of
DEUs.
The
total
number
of
DRU’s
that
can
be
served
is
limited
by
the
cumulative
noise
effect
caused
by
antenna
combining.
This
number
cannot
be
determined
until
the
radius
distance
of
coverage
required
at
the
DRU
antenna
is
determined
and
the
path
loss
attributed
to
the
structure
are
known.
The
system
design
requires
that
the
carrier
to
noise
differential
be
greater
than
the
customer’s
desired
signal
to
noise
ratio.
If
it
is
likely
that
the
system
will
be
expanded
in
the
future,
locate
the
DHU
in
such
a
way
that
it
can
either
be
used
as
a
hub
for
an
expanded
system
or
replaced
with
a
DEU
which
is
then
connected
to
a
relocated
DHU.
It
should
also
be
noted
that
a
DEU
can
be
used
as
an
optical
regenerator.
A
DRU
may
sometimes
need
to
be
located
at
a
point
that
is
beyond
the
500
or
750
meter
limit
(depending
on
fiber
type)
imposed
by
the
optical
link.
The
solution
is
to
install
a
DEU
at
the
maximum
optical
link
limit
(500
or
750
meters)
from
the
DHU.
This
provides
an
additional
500
or
750
meters
of
optical
link
beyond
the
DEU
for
connecting
the
DRU.