Download Power supply via optical fibre in home telematic - SIGMA-NOT

Waldemar WÓJCIK, Zbigniew LACH, Andrzej SMOLARZ, Tomasz ZYSKA
Lublin University of Technology, Department of Electronics
Power supply via optical fibre in home telematic networks
Abstract. The article shows a concept of development of full optical home networks. Forecasts of development of supporting technologies has been
done as well as scenarios of development of systems based on technology in question. The article also marks some goals to be achieved in order to
make the technology market available.
Streszczenie. W artykule pokazano koncepcję w pełni optycznych sieci domowych. Wykonano prognozy dotyczące wspierających technologii
a także opracowano możliwe scenariusze rozwoju systemów opartych na tych technologiach. W artykule pokazano również cele, które powinny
zostać osiągnięta aby technologia ta stała się dostępna na rynku. (Optyczne zasilanie sieci domowych).
Keywords: home network, optical fiber, photovoltaic cell.
Słowa kluczowe: sieć domowa, światłowód, ogniwo fotowoltaiczne.
Optical power supply in home telematic networks
The principle of the remote powering technology
consists in emission, basically from some central device, of
high power continuous optical signal through a fibre-optic
link and its conversion, by means of a photovoltaic module,
into electrical power that can be used to supply the
electronic components. One drawback of the idea of
transmitting optical power via a telecom fiber is that fibers
introduce distortions to the transmitted signals at high
power values. Consequently, one can expect limitations to
practical realization of supplying optically electronic
appliances. In order to identify, whether this limits constitute
a real bottleneck a survey of electronic appliances and
typical network communication devices was performed.
The results are summarized in the following.
Table 1. Trends in ICs’ development
Year
Parameter
Layer thickness
[μ]
Wafer size [mm]
Min. supply
voltage [V]
Max power
dissipation [W]
Clock frequency
[MHz]
DRAM capacity
[GB]
1997
2001
2003
2012
2020
0.25
0.15
0.13
0.05
<10
200
300
300
450
Molec./
Biolog.
1,82,5
1,21,5
1,21,5
0,50,6
<0,001
70
110
130
175
600
750
1500
2100
10
0.256
2.0
4.0
256
5
–5
>5⋅10
5
> 1000
0,1
0,09
power consumption per
megahertz of processor
clock
linear trend
power per unitary frequency [W/MHz]
Introduction
Looking from the present perspective it seems that in
the future most of the home management and/or control
services will be integrated in one device located inside the
home. Such solutions already exist in very fragmented form.
There are several systems that allow simple management
tasks being sold under the name “intelligent building”.
After the launching of several modalities of the so called
set-top boxes including the „Livebox” which generally are
capable to centralize all the telecom and multimedia
services in the home, maybe we have to think about
extending its capabilities with other home services like
management and control of the home. Adding the module
of home security management is the simplest and justified
step. In the future such device may become a centre of
home management.
Nowadays we basically use two transmission media
types in home networks – copper and air. The first one
offers quite resonable bandwidth of tens of megabits per
second and the second one brings the flexibility of location.
Both of them are reaching limits of their technological
capabilities. Now let us assume that the future home
networks are entirely optical. There is no problem with
passive devices, but active devices have to be supplied with
electrical energy. It can be done using a local mains or
battery supply. However, such solution is marked by
a series of disadvantages like for example constraint of
location, unknown reliability, difficult maintenance or (still)
high cost. In the case of fiber optic networks the remote
optical powering can be the method which avoids the use of
a local power supply via a power line and/or batteries to
power and monitor active components.
0,08
0,07
0,06
0,05
0,04
0,03
0,02
0,01
0
1995
2000
2005
year
2010
2015
Fig. 1. Schematic diagram of measurement setup
As we look at the table 1 and the figure 1 we can see
that there is a decreasing ratio of power consumption to
both clock frequency and memory capacity. It allows us to
forecast that capacity of optical power supply can meet the
power demand of the consumer’s devices in future.
Nevertheless, we are not sure if such gross estimation is
sufficient, so first we have to group the devices in
dependence on foreseen power consumption.
1. Low power consumption
• passive intrusion sensors,
• fire, smoke, gas and other detectors,
• coders, selectors, small displays
• local modems
2. medium power consumption
PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 3/2008
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• switches, multiplexers,
• filters, attenuators,
• signalling devices
3. high power consumption
• sound and video converters and processors,
Table 2. Trends in ICs’ development
Component
electrical
power
Low power consumption
intrusion detection
0
fire detection
1mW
smoke detection
1mW
movement
5mW
detection
Communication
10mW
circuits
Telemetry
1mW
SFC – signal
forming circuit
Medium power consumption
Telephone
50mW
High power consumption
TV & Radio over
1W
IP Decoder
TV & Radio
1W
analogue Decoder
Optical signalling
Simple video
0.5 to
converters (Icams,
1W
small displays)
optical
power
*0 (+SFC)
*0 (+SFC)
*0 (+SFC)
10mW
Remarks
Passive
20mW
1mW
considered
below
100mW
Maximally
simplified
2W /?
2W /?
1W
1 to 2W
If it comes to communication devices, the currently
available USB devices have a natural limitations of 2.5 W. It
is much far beyond the limit that optical power transmitted
via a telecom fiber can afford. If we consider Gigabit
Ethernet we also see that currently available 1Gb link ICs
are quite power consuming. For example RTL8139 series
consume at least 900 mW at 3.3 V power supply, according
to the manufacturer (Realtek). It results in about 2 W of
optical power needed for each device when typical value of
40% PPC efficiency is considered. As it can be seen the
„conventional” solutions are not valid. FPGA based Xilinx
solutions may be better for the second approach – they
need about 200 mW.
Another factor that has to be considered is that the
continuous operation is not always needed. Usually
modems transmits in “bursts” which ecourages to exploit an
idea of accumulation of energy in the power supply device.
According to the idea, energy is accumulated over certain
time before it is used. One can expect that the practical
minimum of the supply power for a device, which operate in
burst mode with very low cycle, can limited by the
consumption of electronic driving circuitry in the power
supply device itself.
Let us consider an example of optically powered phone.
According to G.711u [1] – 64 kbps band is needed. In the
GPON [2] network the link time coefficient is then about
–4
5⋅10 and adding some extra margin for initialization and
–4
termination it can be estimated to about 6⋅10 . The power
consumption during transmission is estimated to be
500mW. Taking into account the efficiency of light to
electrical energy conversion and efficiency of accumulation
we get that the energy needed is about 1mWs. It means
that we do not need so much optical power if we can
accumulate energy.
This concept may be extended to “full-speed”
transceivers provided two conditions are satisfied. First that
we operate in a TDM mode. For example, in the case of
278
a complete typical TDM PON (64 users) an individual user
th
has a chance to transmit every 64 time slot. It is the
central control unit (OLT) that controls the transmission so if
the traffic control protocol is aware of the power
accumulating transceivers it can arrange the schedule in
such way which allows recovery of the charge. The second
condition is that the network is complete because in the
sparse network timeslots can be assigned more frequently
so there may be not enough time to recover the energy
status of the transceiver.
Considering the above results and discussion we
propose a concept of introducing optical supply to the
appliances which can be connected to a fiber optic home
network. Being conscious of limitations of contemporarily
available technology, we suggest two system evolution
scenarios depending on technology and market state of the
art and the customer necessities.
The first one may be the first step in introducing
photonics into the home telecom appliances. It basically
consists in expanding the existing functionality of the set-top
box with the optical remote powering and optically powered
user terminals. A sort of modular approach.
The second one supposes remote optical powering of
the set-top box. It is contemplated as photonic solution with
some electrical add-ons. It is meant to be a future oriented
solution; new technologies need to be developed as well as
new power optimized specialized ICs with advanced power
saving functionality.
Solution 1
It assumes modular set-top box with remote optical
powering and local electrical power supply. The minimum
requirement for the set-top box is, the device should be
equipped with optically powered phone. There are following
advantages of such solution:
• Phone service fully protected against mains failures
(independence on external power supply
• Full control of the service from the central office to the
receiver,
• Electrical powering of modem allows alleviation of
central office even in case of increasing service
capability,
• Easier distribution of optical supplying power,
• It is possible to power optically more consuming
devices like detectors, TV decoders or advanced
phone.
There is one disadvantage for this solution. It is:
• In case of failure in supply of electrical energy most of
“Livebox” extensions cease to operate. It is assumed
that “emergency” phone is optically supplied in its basic
functionality so the problem reporting is possible.
Solution 2
It assumes remote optical powering of the entire Livebox.
The requirements include: optically powered phone and
optically powered modem for basic data connection.
According to these requirements the two services: phone
and data will persist even in case of local power failure (we
allow data link to slow-down in this case). Other devices
may be connected later in dependence on each technology
(basically after decrease in power consumption). The main
advantages of this solution are as follows:
• Independence on external power supply
• Full control of the service from the central office to the
receiver.
The solution has also few disadvantages, which can be
briefly listed:
• Low efficiency of currently available PPCs.
• Transmission of high optical power is necessary
PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 84 NR 3/2008
• Application of separate optical power supply fibre may
be necessary.
• Advanced technologies of optical user safety are
required (e.g. in case of breaking the fibre),
• Fire safety is unknown,
• Aggregation of functionality is necessary e.g. DVB
decoder integrated in DVD recorder allows avoiding
necessity to power the decoder in optical way.
Conclusions
Supplying optically a terminal and other devices, which can
be connected to them, practically cannot be solved at
present. For the purpose of structuring possible
development actions we propose to distinguish separate
classes of optically supplied devices:
• 1st class, which contains the analogue part of
a terminal; the 1-st class would be obligatory supplied
optically
• 2nd class, which contains blocks of the slowest
transmission speed (it may include POTS-to-network
interface and possibly a Bluetooth modem); it could be
supplied optically in the next stage of development
• 3rd class; which contains other devices; the devices
belonging to this class as well as their interfaces to the
network would be supplied externally.
We also suggest to start a research on a low-power
moderate speed interface to optical network (transmission
convergence block). The possibility to realize such
interface, and possibility for including it into the optically
supplied class 1, may be of primary interest of future
operators of PONs, for some services should be offered
without restrictions from the availability of local supply.
The key for supplying power to a transceiver via fibre is the
minimization of power consumption of many blocks, which
at present consume watts or hundreds of milliwats. One can
reject idea of supplying optically lots of terminals from a
central site like in favour of supplying them (if necessary)
from a local optical source. The USB-like network can be
one candidate solution.
Acknowledgments: The core of this research was financed
by France Telecom.
REFERENCES
[1] ITU-T, “G.711 -” (03/2003)
[2] ITU-T, “G.984.1 - Gigabit-capable Passive Optical Networks
(GPON): General characteristics” (03/2003)
[3] Lach Z., Smolarz A., Wójcik W., Tymecki A., Experimental
validation of an optical supply for an electrooptic switch,
Przeglad Elektrotechniczny, 84 (2008), nr.3, 259-261
Authors:
dr hab. inż. Waldemar Wójcik, prof. PL; dr inż. Zbigniew Lach;
dr inż. Andrzej Smolarz; mgr inż. Tomasz Zyska; University of
Technology, Department of Electronics, Nadbystrzycka 38a,
20-680 Lublin, Poland; E-mail: wal;[email protected];
E-mail: [email protected]; E-mail: [email protected];
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