ASSEMBLY COMPRISING AT LEAST ONE OPTICAL FIBRE AND A
MOUNTING DEVICE
FIELD OF THE INVENTION
The invention relates to an assembly comprising at least one optical fibre
and a mounting device and to a method for mounting the assembly.
BACKGROUND
In conventional cellular mobile communication systems such as GSM (GSM
Global System for Mobile Communication) a connection between a base
station and an on-site antenna is usually a copper-wire. The base station
modulates downlink data into downlink high-frequency signals using an
allocated frequency band for example around 900 MHz and a power
amplifier of the base station amplifies the downlink high-frequency signals.
The amplified downlink high-frequency signals are transmitted usually via a
coaxial cable to the on-site antenna and the on-site antenna emits the
amplified downlink high-frequency signals forming a radio cell of the base
station. The radio cell is for example split into 3 radio sectors with a 1 0
degree of arc coverage of each radio sector or into 6 radio sectors with a
60 degree of arc coverage of each radio sector. Each radio sector is served
by a separate antenna. Conventionally, communication links between the
base station and the antennas are separated in uplink communication links
and downlink communication links. This means that usually 6 or coaxial
cables are installed between a base station rack of the base station and the
antennas of the base station.
In future radio communication systems, the energy consumption shall be
reduced to reduce the OPEX (OPEX = operating costs) and to provide a
contribution for limiting the global warming problem.
In typical 7/8 inch coaxial cables with a length of 30 m, approximately 35
percent of the transmitted signal power is lost by absorption and/or
scattering and cannot be used for serving the radio ce l of the base station.
In comparison to the coaxial cables, optical fibres have an attenuation of
less than 1 dB/km. Therefore, new base stations and more and more
existing base stations are using optical fibres for a transmission of data
between the base station and the antenna instead of the coaxial cables
according to an FTTA concept (FITA = fibre to the antenna). Based on this
concept, power amplifiers are located in radio remote heads close to the
antenna. Thereby, the power amplifiers do not have to compensate for any
cable losses. Furthermore, due to the low losses of the optical fibres radio
remote heads and antennas can be installed with a larger distance to the
base station and/or power amplifiers with a smaller overall output power
can be used.
Data rates in future radio communication systems such as HSPA (HSPA =
High Speed Packet Access) or LTE (LTE = Long Term Evolution) will be
increased by using a MIMO transmission (MIMO = multiple input multiple
output) between the base station and a mobile station. This requires
additional or new connections to be installed between the base station and
the location of MIMO antenna systems.
SUMMARY
If existing base stations are upgraded to FTTAthe coaxial cables between
the base station rack and the antenna may be uninstalled and may be
replaced by a fibre-optic cable comprising optical fibres for the data
downlink und the data uplink to be connected between the base station
rack and the radio remote head and by an electrical cable for the power
supply of the radio remote head.
The way of upgrading existing base stations affects installation costs and
installation effort.
Therefore, it is an object of the invention to reduce the installation costs and
the installation effort.
The object is achieved by an assembly comprising one or several optical
fibres and a mounting device. The one or several optical fibres protrude
from the mounting device, so that the one or several optical fibres can be
inserted to a tube. The mounting device is adapted to terminate the tube
and preferably hermitically seals an end face of the tube.
The object is further achieved by a method for mounting the assembly,
wherein the method comprises the steps of inserting into the tube the one or
several optical fibres of the assembly protruding from the mounting device
of the assembly; and terminating the end face of the tube with the mounting
device.
The mounting device may be for example a sleeve, an adapter or a
connector with a holding fixture for the one or several optical fibres and a
clamping fixture for terminating the tube or may comprise a separate
retainer for the one or several optical fibres and a cable gland for mounting
the retainer to the end face of the tube.
The one or several optical fibres may be single-mode or multi-mode fibres.
The tube may be for example a coaxial cable with an inner hollow cylinder
and the inner hollow cylinder may be adapted to comprise the one or
several optical fibres.
The invention has a first benefit with respect to already installed base
stations of reusing one or several of the installed coaxial cables for inserting
the one or several optical fibres. Installation costs can be reduced because
the optical fibres don't need a special cable jacket for outdoor use. The
installed coaxial cable will act as the cable jacket for the one or several
optical fibres.
The invention has a second benefit of providing a prepared installation kit.
An installer gets to the location of the radio remote head, cuts an existing
coaxial connector of the coaxial cable previously mounted to the antenna
and threads the one or several optical fibres through the coaxial cable
towards the location of the base station. There is no need to uninstall the
installed coaxial cable at the antenna mast and to install a new optical fibre
cable system at the antenna mast. Thereby, the installation can be easier
performed (no installation work along the antenna mast) and the
installation time is considerably reduced.
The invention provides a third benefit of hermetically sealing the end face of
the tube by terminating the tube with the mounting device. Thereby, the one
or several optical fibres are protected against environmental impacts such
as humidity.
The invention provides a fourth benefit of providing a mechanically stable
transition from the tube to the exposed optical fibres avoiding any
mechanical stress for the optical fibres.
Further advantageous features of the invention are defined and are
described in the following detailed description of the invention.
BRIEF DESCRIPTION O F THE FIGURES
The embodiments of the invention will become apparent in the following
detailed description and will be illustrated by accompanying figures given
by way of non-limiting illustrations.
Figure 1 shows schematically a block diagram of an assembly in a crosssectional
view according to an embodiment of the invention.
Figure 2 shows schematically a flow diagram of a method for mounting the
assembly according to the embodiment of the invention.
Figure 3 shows schematically a block diagram of a base station according
to an application of the invention.
DESCRIPTION OF THE EMBODIMENTS
Figure 1 shows schematically a block diagram of a n assembly AS in a
cross-sectional view according to a n exemplarily embodiment of the
invention. The assembly AS comprises a mounting device EF and for
example a first optical fibre FB , a second optical fibre FB2, a third optical
fibre FB3, a fourth optical FB4, a fifth optical fibre FB5, and a sixth optical
fibre FB6 protruding from the mounting device EF. In further alternatives,
the assembly AS comprises less or more than six optical fibres protruding
from the mounting device EF. The optical fibres FBI to FB6 may be singlemode
o r multi-mode fibres.
Preferably, the optical fibres FBI to FB6 protrude from a first front side of
the mounting device with a n emersion length, which is adapted to a length
of a tube TUB in which the optical fibres FBI to FB6 can be inserted. More
preferably, the emersion length is larger than the length of the tube TUB.
The mounting device EF may be for example a sleeve, a n adapter o r a
connector for connecting the mounting device EF to a unit such a s a radio
remote head.
The mounting device EF a s a n end fitting for the tube TUB may comprise
preferably a separate retainer RET for inclusion of the optical fibres FB to
FB6 and a fixation unit FU for mounting the retainer RET to a n end face of
the tube TUB. The fixation unit FU may be for example a cable gland. The
cable gland may comprise for example a cap nut CN of Polyamid 6 and a
sealing SEAL of Neoprene. The cap nut CN comprises a n internal screw
thread 1ST to be screwed to a n outer screw thread OST of the retainer RET.
The sealing SEAL is located within the cap nut CN and is for example a ring
with a n inner diameter slightly smaller than a n outer diameter of the tube
TUB.
Alternatively, the fixation unit FU may be a locking ring to be shifted onto
the end face of the tube TUB with an inner diameter slightly smaller than an
outer diameter of the tube and with barbs on an inner surface directed
towards an outer surface of the tube TUB or may be a heat shrinkable
tubing.
In a further alternative, the mounting device EF may be a single workpiece
with a retainer functionality for the optical fibres FBI to FB6 and a fixation
functionality for fixing the mounting device EF to the tube TUB.
The retainer RET may be split preferably into a first hollow cylinder with a
first inner diameter for fixing the optical fibres FBI to FB6 and a second
hollow cylinder with a second inner diameter larger than the first inner
diameter for providing a counterpart for the cable gland. The second inner
diameter and an outer diameter of the second hollow cylinder may be
adapted to dimensions of the fixation unit FU such as the diameter of the
internal screw thread 1ST and an outer diameter of the sealing SEAL.
A material of the retainer RET may be for example aluminium, stainless
steel, Polyamid 6, Polyethylene (PE = polyethylene) or polyvinyl chloride
(PVC = polyvinyl chloride). The optical fibres FBI to FB6 are preferably
located centrally along a longitudinal axis of the first hollow cylinder.
In a first alternative, the optical fibres FBI to FB6 range from a first end face
of the retainer RET to a second end face of the retainer RET and protrude
from the first and the second end face of the retainer RET.
In a second alternative as shown in Figure 1, the optical fibres FB to FB6
are terminated inside the retainer RET by splices at a position POS.
Preferably the position POS is located within a middle third of a length of
the first hollow cylinder.
The optical fibres FBI to FB6 extend from the splices for example by a first
outdoor pigtail PIGT1 , by a second outdoor pigtail PIGT2, and by a third
outdoor pigtail PIGT3. The outdoor pigtails PIGT1 to PIGT3 are adapted for
use under outdoor environmental conditions.
The first outdoor pigtail PIGT1 may comprise a seventh optical fibre FBI ,
which is spliced to the first optical fibre FBI and may comprise an eighth
optical fibre FB2_2, which is spliced to the second optical fibre FB2. The
second outdoor pigtail PGT2 may comprise a ninth optical fibre FB3_2,
which is spliced to the third optical fibre FB3 and may comprise an tenth
optical fibre FB4_2, which is spliced to the fourth optical fibre FB4. The third
outdoor pigtail PIGT3 may comprise an eleventh optical fibre FB5_2, which
is spliced to the fifth optical fibre FB5 and may comprise a twelfth optical
fibre FB6_2, which is spliced to the sixth optical fibre FB6.
The outdoor pigtails PIGT1 to PIGT3 may comprise protective tubes
enclosing in each case two of the optical fibres FB1_2 to FB6_2.
In further alternatives, the outdoor pigtails comprise one optical fibre or
more than two optical fibres.
In a further alternative, indoor pigtails may be used instead of the outdoor
pigtails PIGT1 to PIGT3, if the assembly AS may be applied according to an
indoor application or if the assembly AS is located at a transition from an
outdoor location comprising the tube TUB to an indoor location comprising
the indoor pigtails.
The optical fibres FBI to FB6 are fixed within the retainer RET for example
by a filler material F . Preferably, a cross section of the first hollow
cylinder, which is perpendicular to a longitudinal axis oriented from the first
front side of the fixation unit FU to a second front side of the fixation unit FU
is filled with the filler material FM. Thereby, the filler material FM may
enclose the splices and may have also a sealing functionality for the end
face of the tube TUB.
More preferably, the filler material FM fills out a complete hollow space of
the first hollow cylinder.
The filler material FM may be for example a two-component adhesive,
epoxy, silicon, vulcanized rubber or polyurethane (PU = polyurethane). The
first inner diameter of the first hollow cylinder may be adapted to a number
of the optical fibres FBI to FB6. Furthermore, the first inner diameter of the
first hollow cylinder may be adapted to a flow behaviour of filler material
FM in a molten or liquid state.
The filler material FM preferably encloses the optical fibres FBI to FB6 over
the length of the first hollow cylinder. The length of the first hollow cylinder
may be adapted to a consistency or stiffness of the filler material FM and/or
to a mechanical force impacting on the optical fibres FBI to FB6 during
operation of the optical fibres FBI to FB6. The filler material FM preferably
enclose the optical fibres FB to FB6 over a length of the optical fibres FBI
to FB6 in a range between 1 cm and 10 cm.
Preferably, distances between end pieces of the optical fibres FBI to FB6
within the first inner hollow cylinder are larger than distances between the
optical fibres FBI to FB6 protruding from the mounting device EF. This
allows the filler material FM to get between the end pieces of the optical
fibres FBI to FB6 and to enclose each of the end pieces of the optical fibres
FBI to FB6 separately. Thereby, the fixation for the optical fibres FBI to FB6
can be improved.
The second hollow cylinder of the retainer RET is preferably not filled with
the filler material FM and is instead filled by a n environmental gas EG,
which is for example air.
The assembly AS may further comprise the tube TUB (see Figure 1). The
mounting device EF is mounted to the end face of the tube TUB and the
fibres FB to FB6 penetrate the tube TUB from the end face of the tube TUB
to an opposite end face of the tube TUB.
An outer perimeter of an end piece of the tube TUB is preferably enclosed
by the sealing SEAL of the fixation unit FU.
The tube TUB may be for example a hollow cylinder with a flexible jacket
made from a plastic, silicon or rubber material. Preferably, the tube TUB
may be a coaxial cable with an inner hollow conductor IC, an outer hollow
conductor OC, an isolation material ISO between the inner hollow
conductor IC and the outer hollow conductor O C and a cable jacket CJ.
The outer hollow conductor OC may be for example a corrugated outer
conductor as shown in Figure 1.
An inner diameter of the inner hollow conductor C is adapted to comprise
the optical fibres FBI to FB6 and is larger than an overall outer diameter of
a closely grouped arrangement of the optical fibres FBI to FB6.
In an alternative, the tube TUB may be a cable with one hollow conductor
for inclusion of the optical fibres FBI to FB6.
Referring to Figure 2 a flow diagram is shown of a method MET for
mounting the assembly AS as shown in Figure 1 to the tube TUB as shown
in Figure 1.
The sequence and the number of the steps for performing the method MET
is not critical, and as can be understood by those skilled in the art, that the
sequence and the number of the steps may vary without departing from the
scope of the invention.
The method MET is exemplarily described with respect to an application of
the invention for an upgrade of an existing base station of a radio
communication system. A person skilled in the art may easily adapt the
method MET for other applications of the invention.
In a first step Ml , an installer of a mobile radio vendor or of a mobile radio
operator may carry the assembly AS comprising the optical fibres FBI to
FB6 and the mounting device EF to a top section of an antenna mast or to a
roof of a building equipped with an antenna system.
In a further step M2, the installer may disassemble a connection between a
coaxial cable TUB and the antenna system. The disassembly may be
performed for example by removing a coaxial connector terminating the
coaxial cable TUB or by simply cutting the coaxial cable TUB near the
coaxial connector.
In a further step M3, the cab nut CN of the cable gland may be plugged on
an end piece of the coaxial cable TUB.
In a next step M4, the installer inserts end pieces of the optical fibres FBI to
FB6 protruding from the mounting device EF into the inner hollow
conductor IC of the coaxial cable TUB. In an alternative, the insertion may
be performed automatically by a tool by aligning the optical fibres FBI to
FB6 centrally according to the end face of the coaxial cable TUB and by
moving the optical fibres FBI to FB6 towards the end face of the coaxial
cable TUB. This automatically alignment may prevent any damages to the
optical fibres FBI to FB6.
In further repeated steps M5, the installer slides the optical fibres FBI to FB6
stepwise into the inner hollow conductor IC of the coaxial cable TUB until
the mounting device EF comes close to the end face of the coaxial cable
TUB. In an alternative, the tool picks the optical fibres FBI to FB6 stepwise
and moves the optical fibres FBI to FB6 stepwise towards the end face of
the coaxial cable TUB.
Thereby, the optical fibres FB to FB6 slip stepwise through the coaxial
cable TUB.
In a next step M6, the installer terminates the end face of the coaxial cable
TUB with the mounting device EF for example by screwing the cap nut to the
retainer RET. Thereby, the end face of the coaxial cable TUB may be in
contact with the filler material FM of the first hollow cylinder or there may
exist a hollow space between the filler material FM and the end face of the
coaxial cable TUB in a longitudinal direction of the optical fibres FBI to
FB6.
In an alternative, the tool may automatically execute the termination by
mounting the cap nut with a predefined torsional moment at the retainer
RET.
Figure 3 shows schematically a block diagram of a base station BS
according to an application of the invention. The elements in Figure 3 that
correspond to elements of Figure 1 have been designated by same
reference numerals.
The base station BS comprises basically a base station rack BSR, an
antenna system ANTSYS, a feeder cable FC for providing electrical power
from the base station rack BSR to the antenna system ANTSYS and an
optical fibre connection OFC for transmitting user and signalling data
between the base station rack BSR and the antenna system ANTSYS.
The base station rack BSR may be located for example at ground level and
the antenna system ANTSYS may be located on top of a roof of a building
or on top of a freestanding antenna mast.
The base station rack BSR comprises a base band unit BBU and a power
supply PS. The base band unit BBU is adapted to provide preferably digital
optical signalling data or user data to be transmitted to radio remote heads
RRH1 , RRH2, RRH3. The radio remote heads RRH1 , RRH2, RRH3 are
adapted to transform the optical downlink data into radio frequency signals
and to provide the radio frequency signals to the antenna system ANTSYS.
The antenna system ANTSYS transmits the radio frequency signals to mobile
stations connected via wireless links to the base station BS. A corresponding
processing is provided in the uplink direction from the mobile station via the
antenna system ANTSYS and the radio remote heads RRHl , RRH2, RRH3 to
the base band unit BBU. This is common knowledge and therefore not
explained in more detail.
Preferably, the base station BS further comprises a fuse box FB in a short
distance to the power supply PS with fuses for overvoltage and lightning
protection purposes for conductors of the feeder cable FC and jumper
cables JC , JC2, JC3, JC4.
The power supply PS may be connected to the fuse box FB with a first
jumper cable JC1 . The feeder cable FC may be connected with a first end
piece to the fuse box FB and with a second end piece to a distribution box
DB. The distribution box DB provides an electrical parallel connection for
connecting the jumper cables JC2 to JC4. A second jumper cable JC2 is
connected to a power supply port of a first radio remote head RRHl . A third
jumper cable JC3 is connected to a power supply port of a second radio
remote head RRH2. A fourth jumper cable JC4 is connected to a power
supply port of a third radio remote head RRH3.
The radio remote heads RRHl , RRH2, RRH3 comprises one or several
antennas ANT1 , ANT2, ANT3 for radio links between the radio remote
heads RRHl , RRH2, RRH3 and one or several mobile stations such as
mobiles, notebooks or PDAs (PDA = personal digital assistant).
Preferably, each radio remote head RRHl , RRH2, RHH3 provides radio
coverage for a separate sector of a radio cell of the base station BS.
The optical fibre connection OFC may comprise the tube TUB, the mounting
device EF, the optical fibres FBI to FB6 and the outdoor pigtails PIGT1 to
PIGT3.
The optical fibres FBI , FB2 and the first outdoor pigtail PIGT1 are
connecting the base band unit BBU with the first radio remote head R H 1.
Preferably, a first one of the fibres FBI , FB2 is used for a downlink
connection from the base band unit BBU to the first radio remote head
RRH1 and a second one of the fibres FBI , FB2 is used for an uplink
connection from the first radio remote head RRH1 to the base band unit
BBU. Similarly, the optical fibres FB3, FB4 and the second outdoor pigtail
PIGT2 may be connecting the base band unit BBU with the second radio
remote head RRH2 and the optical fibres FB5, FB6 and the third outdoor
pigtail PIGT3 may be connecting the base band unit BBU with the third
radio remote head RRH3.
Alternatively, the optical fibre connection OFC may comprise for each of the
radio remote heads RRH1 to RRH3 a single optical fibre for connecting the
base band unit BBU to one of the radio remote heads RRH1 to RRH3. In
such a case, downlink and uplink signals may use different optical
wavelengths and optical add-drop multiplexers may be used at the base
band unit BBU and the radio remote heads RRH1 to RRH3 for adding and
dropping the optical wavelengths.
In further alternatives, the base station BS may comprise less o r more than
three radio remote heads and the assembly AS comprises less or more than
six optical fibres.
CLAIMS
1. An assembly (AS) comprising a t least one optical fibre (FBI FB6) and
a mounting device (EF), said at least one fibre protrudes from said
mounting device (EF), and said mounting device (EF) is adapted to
terminate a tube (TUB) for inserting said at least one optical fibre (FBI ,
FB6).
2 . Assembly (AS) according to claim , wherein a cross section of a hollow
space inside said mounting device (EF) and perpendicular to a
longitudinal axis oriented from a first front side of said mounting device
(EF) to a second front side of said mounting device (EF) is filled with a
filler material (FM).
3 . Assembly (AS) according to claim 2 , wherein said filler material (FM)
encloses a splice for said at least one optical fibre (FBI , FB6).
4 . Assembly (AS) according to claim 3 , wherein said at least one optical
fibre (FBI , FB6) is extended from said splice by a n outdoor pigtail
(PIGT1 , PIGT3).
5 . Assembly (AS) according to any of the claims 2 to 4 , wherein said filler
material (FM) is a two-component adhesive, epoxy, silicon o r vulcanized
rubber.
6 . Assembly (AS) according to any of the claims 2 to 5 , wherein said filler
material (FM) encloses said a t least one optical fibre (FBI , FB6) over
a predefined longitudinal length of said at least one optical fibre (FBI ,
FB6) and wherein said predefined length is adapted to a consistency
and/or stiffness of said filler material (FM) and/or to a mechanical force
impacting on said at least one optical fibre (FBI , FB6).
7. Assembly (AS) according to claim , wherein said predefined length is in
a range between cm and 10 cm.
8 . Assembly (AS) according to any of the preceding claims, wherein said
assembly (AS) further comprises said tube (TUB), wherein said mounting
device (EF) is mounted to an end face of said tube (TUB) and wherein
said at least one fibre penetrates said tube (TUB) from said end face to
an opposite end face of said tube (TUB).
9. Assembly (AS) according to claim 8, wherein said mounting device (EF)
comprises a first cylindrical part (RET) completely or partly filled with said
filler material (FM) and a second part (FU) mounted to said first
cylindrical part (RET) and mounted to said end face of said tube (TUB).
lO.Assembly (AS) according to claim 9, wherein said second part (FU) is a
cable gland.
1 .Assembly (AS) according to any of the preceding claims, wherein said
tube (TUB) is a coaxial cable with an inner hollow conductor (IC) and
wherein said inner hollow conductor (IC) is adapted to comprise said at
least one optical fibre (FBI , FB6).
12.A Base station (BS) comprising said assembly (AS) according to claim 8,
9, O or 11.
13. Method (MET) for mounting an assembly (AS), said method (MET)
comprising the steps of:
- inserting (M4) into a tube (TUB) at least one optical fibre (FBI , FB6)
of said assembly (AS) protruding from a mounting device (EF) of said
assembly (AS); and
- terminating (M6) an end face of said tube (TUB) with said mounting
device (EF).