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Multi-dwelling unit (MDU) greenfield-and-overbuild-/' class='doin' >Applications for greenfield and overbuild scenarios - 105892AE
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Multi-dwelling unit (MDU)
greenfield-and-overbuild-/' class='doin' >Applications for greenfield
and overbuild scenarios Multi-dwelling unit (MDU)
greenfield-and-overbuild-/' class='doin' >Applications for greenfield and overbuild scenarios
Deploying fiber to MDUs, such as apartment complexes, condominiums,
townhouses, and other multi-family locations, represents a lucrative market for
broadband service providers. At the same time, these applications present unique
challenges in both greenfield and overbuild scenarios. This paper addresses the
key elements of MDU construction practices, including the physical plant from
backbone to premise and the architectural decisions required for a successful
MDU application. It will also cover additional network considerations for
equipment and connectivity techniques.
MDU connection strategies for fiber-to-the-premise (FTTP) deployments will differ
from site to site and the type of structure will often dictate the strategies for
fiber cabling and connections within the structure. In every case, there are key
building blocks that include indoor and outdoor fiber distribution hubs (FDHs),
fiber distribution terminals (FDTs), riser cables, drop cables, raceway systems, and
wall plates. MDU applications typically require additional drop cables, raceways,
and outlets for completing the interconnection and extending fiber into every
living unit. Multi-dwelling unit (MDU) greenfield-and-overbuild-/' class='doin' >Applications for greenfield and overbuild scenarios
Page 3
The MDU architecture
Every MDU is served by at least one telecommunications
room (TR). Ideally, there is one TR per floor that is
recognized as the connection point between the
backbone cabling connection to the central office (CO) or
head-end and the horizontal pathways and cabling to the
living units or office spaces (see Figure 1).
The backbone cable of an MDU architecture refers
to the fiber-optic riser cable in multi-floor buildings,
but generally refers to the pathway between entrance
facilities, equipment rooms, floor-serving terminals,
TRs, common equipment rooms, or common
telecommunications rooms. TRs will typically house the
entrance facilities and the main cross-connect, horizontal
cross-connect (floor distributor), and intermediate cross-
connect (building distributor).
Vertically-aligned TRs with connecting sleeves or slots are
the most common types of backbone pathways. They
offer better flexibility by providing accessibility to the
backbone cable sheath on each floor and enable circuits
to be distributed as needed. It should be noted that
proper fire-stopping techniques should
be maintained at all times.
With TRs aligned in a vertical pathway, a means for cable
pulling should be provided in line with the sleeves or
slots at the uppermost room of each vertical stack,
such as a steel anchor pulling iron or an eye-bolt
embedded in the concrete. Where pulling irons are
not available, the building steel may act as a sufficient
pulling mechanism location.
A goal should be to position cable sleeves or slots
adjacent to a wall that can support backbone cabling.
However, sleeves or slots cannot obstruct wall
terminating space by placement above or below the wall
space intended for termination fields. Modifications or
changes to any MDU structure must be approved by a
structural engineer. Further, all sleeves and slots must
conform to all national and local building and fire codes.
The backbone or riser cable in a vertical riser shaft
may be extremely heavy (high strand count) optical fiber
cable. There are several considerations for deciding the
best method of installation. The preferred practice is to
place the fiber-optic riser cable into a vertical pathway
from the top down. There may also be tensile strength
considerations in the cables manufacturing specifications.
The cable can be placed vertically in an open riser shaft;
through cores, sleeves, or slots; or within a large conduit.
The cable installer should determine the size and type of
reel for loading the cable, particularly in a high-rise MDU
situation where the cable must be spooled to each floors
TR with enough slack for splicing to a terminal. Cable
lengths must be verified for end-to-end distance do not
rely on the manufacturers cable-run label. The riser cable
should be secured to a back board support by at least
three cable clamps at the top and a single clamp at the
bottom. Slack storage is accomplished by single clamps
above and below each storage spool, with the spool
secured to the back board. Plywood back boards should
be at least � and painted with fire-retardant paint.
Nth Floor
1st Floor
2nd Floor
3rd Floor
4th Floor
5th Floor
6th Floor
7th Floor
1 - 78 mm (3-in) Trade Size
Conduit between TRs minimum
Telecommunications Room (TR)
103 mm (4-in) Trade
Size Conduits
103 mm (4-in) Trade
Size Sleeves
103 mm (4-in) Trade
Size Conduits
Main Terminal/Equipment Room
Entrance Room/Facilities
103 mm (4-in) Trade
Size Conduits
103 mm (4-in) Trade
Size Conduits
TR
103 mm (4-in) Trade
Size Sleeves
Figure 1. Telecommunications Room Multi-dwelling unit (MDU) greenfield-and-overbuild-/' class='doin' >Applications for greenfield and overbuild scenarios
Page 4
FTTP network architectures for MDU applications consist
of four basic building types high-rise (100 or more
living units on 10 or more floors) , medium rise (less than
100 living units on multiple floors), low rise or garden
style (single living units on each floor), and horizontals
(each unit resembling a single family unit). Each building
type presents its own set of unique challenges for the
network installer (see Figure 2).
High-rise and medium rise MDUs
The most difficult MDU applications are typically in
existing high-rise and medium-rise structures, since
the plan must adapt itself to each buildings unique
architectural design. Therefore, there is never a right or
wrong way to install the network the installer must
adapt to the buildings layout and design. Although the
considerations are basically the same for any high-rise,
the techniques and strategies will be different, particularly
in existing structures.
Typically, a feeder cable is routed from the serving
FTTP equipment to the structure and connected to
an indoor FDH located in the basement or other usable
ground-level location. The placement of these cables
must be well thought out. For instance, care must be
taken not to place cabling or electronics within the
elevator shafts. Keep in mind, however, that the location
for the FDH must be secure from intruders and protected
from the elements.
The optical splitting function and connection of the
network within the building is performed in the FDH.
For most MDUs, a centralized splitter configuration
works best. However, circumstances could also dictate
using either a distributed splitter configuration or a
combination of both types.
Riser cables are distributed to the various floors through
established pathways. Because the floor-to-floor access
and entrance to the living units may be limited, new
conduits may be required. Metal tracking systems may
also be used within an existing system. If allowable,
using an existing cable TV infrastructure may be
a viable solution. In any case, proper bend radius
must be maintained throughout the placement
of the riser cabling.
Each FDT is connected to the riser cabling using
connectorized interfaces is recommended for enabling
easy technician access to each living unit for turning up
services, maintenance, and troubleshooting. Drop cables
are installed into each living unit and routed to that
floors FDT. Final interconnections can then be made as
each subscriber requests services. Again, its important
to ensure proper bend radius when routing cables to
and within each living unit.
In a typical greenfield application, the common
equipment room would be located in the basement,
with a common telecom room for every three floors.
Using a centralized architecture, 1x32 splitters are located
at the indoor FDH with a high-count fiber riser cable
extending through the building. The riser cable would
be intercepted with 12-fiber and 24-fiber cables to
each indoor FDT on each floor. Additional drop cables,
raceways and outlets complete the interconnection to
the living units on each floor.
Horizontal
MDU
Central Office
Headend
Residential
Businesses
Indoor Fiber Distribution
Terminal (iFDT)
Indoor Fiber Distr