Furukawa ElectricFurukawa Electric Broadband Involvement in FTTH Systemsby Shunichi Nakamura *With respect to recent rapid expansion of FTTH systems, we present in thispaper an overview of these systems, and report on the development of equipment relating to FTTH transmission and data transmission. Using optical transmission devices
incorporating technologies generated by Furukawa Electric’s R&D activities, we have been able
to configure FTTH systems that are both more efficient and simpler than those formerly in use.

ABSTRACT

work unit (D-ONU) of subscribers. Recently systems areavailable that offer optical wavelength division multiplexing of the broadcast and data transmission services on asingle optical fiber, requiring a cheap yet practical WDMfilter.
We have developed a variety of devices needed to realize this “triple play” in FTTH systems. This paper presents
an overview of FTTH systems, and reports on the development of devices required for the realization video transmission and data transmission services.

INTRODUCTION

In recent years there has been a rapid expansion of fiberto-the-home (FTTH) systems that bring broadband fiberoptic services into the home. FTTH systems provide infrastructure for what may be described as a “triple play”:
broadcasting, data transmission and IP telephony. Since
the beginning of the 1990s, Furukawa Electric has been
engaged in systems studies and R&D aimed at the realization of FTTH services 1).
To provide broadcasting services on FTTH systems it isnecessary the optical broadcast signals be amplified, anddistributed to the video optical network unit (V-ONU) of
subscribers in the most efficient manner.
To provide data transmission services, it is necessary tominiaturize and integrate optical receiver devices, transmitter devices, wavelength division multiplexing filters andcommunications control circuitry into the data optical net-Broadband optical→
Satellite transmission (950〜2602 MHz)
broadcasting, etc.
1550+αnm

Figure 1 shows the configuration of an FTTH system providing broadcasting, data transmission and IP telephonyservices. This configuration is known as the passive optical network (PON) type, and is characterized by a single
optical fiber being shared by a number of subscribers.

→→【Fiber cable】
Optical→→ ampliﬁer→(EDFA)

1550+βnm

High-powermultiport
opticalampliﬁer(EDFA)

Narrow-cast optical transmitter

Community channel, etc.

ＰＩＦ (#1)
ＰＩＦ (#2)

Ethernet(1 Gb/s)→【Subscriber distribution line (optical ﬁber)】→→←
Closurecoupler (& WDM)

WDM (#2)
WDM (#3)

WDM (#n)【Subscriber's service line(optical ﬁber)】ＰＩＦ (#3)
・・・・

OLT

1490nm→←1310nm

WDM (#1)

・・・・【CENTRAL OFFICE】

OVERVIEW OF FTTH SYSTEMS

・・・・

Wavelength
division
multiplexing

Multichannel
1550nmbroadcasting(up to 100 channels) Broadband optical→transmission (70〜770 MHz)

2.

Wavelength
division
multiplexing

1.

V-ONU

ＰＩＦ (#n)【SUBCENTRAL OFFICE】

Multichannel TV

D-ONU

Figure 1

High-speed
Internet& IP telephony

Typical FTTH system configuration.

【FTTH SUBSCRIBER】* Broadband Products Dept., Telecommunications Co.,
Furukawa Electric

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Furukawa Electric Broadband Involvement in FTTH Systems

The broadcasting center is equipped with an opticaltransmitter that converts broadcast signals for multiple
channels into an optical signal in the 1550-nm band. Thisis a device that combines nearly 100 digital channels(analog channel equivalent of about 100 channels anddigital channel equivalent of about 300 to 400 channels ofSDTV quality and about 100 channels of HDTV quality)
into an optical signal. Of optical transmitters there arethose of the external modulation type, in which opticalintensity is modulated in an external modulator distinct
from the laser diode, and those of the direct modulation
type, in which optical intensity is modulated by varying
the current of the laser diode.
The first of these is characterized by the ability to carryan optical signal over long distances with low dispersionfor transmission over a 1.3-μm band zero-dispersion single-mode fiber, so that transmission ranges of over 100
km are possible 2). The second, on the other hand, iscapable of transmission over a wide band of frequencies
up to about 2600 MHz. This is a frequency at which even
the IF signal of satellite broadcasts can be carried without
modification.
After conversion, the optical signal is amplified using
the optical amplifier and split at the splitter. The higher theoutput power of the optical amplifier, the better its efficiency will be. On the other hand, due to the phenomenon of
nonlinearity in the optical fiber, the optical power that canbe injected into the optical fiber is limited (stimulatedBrillouin scattering, etc.) As the scale of an FTTH system
becomes greater, its configuration and operating cost willchange significantly in accordance with the amplifying/
splitting efficiency, space efficiency, and power consumption efficiency of the optical amplifier.
The optical signal distributed by an optical amplifier etc.
(the broadcast optical signal) serves all subscribers withthe same broadcast signal. On the other hand, as the service area becomes larger, it may be necessary to provide
service of an community channel for each audience service area. In such a case it is possible to add to a program by means of a narrowcast optical transmitter that
can add a program directed to a specific area only on anindependent signal of differing wavelength. A communications method using a narrowcast optical transmitter isshown in Figure 1.
The amplified and split optical signal is split in the optical fiber transmission path using an optical coupler, andis received by the subscriber V-ONU, converted into anelectrical signal and fed to the television receiver set.
The data signals, on the other hand, are transmitted bya method known as a GE-PON system. PON interface(PIF) at the optical line terminal (OLT) installed at the central office is connected to as many as 64 subscriber DONUs (when 1 fiber has a 64-way split). The transmission
speed is shared by subscriber terminals connected to 1Gb/s.
Broadcast signal and data signal services may be provided by wavelength division multiplexing, and are multiplexed at the central office using a WDM filter and are split
similarly at subscribers premises.

3.

VIDEO TRANSMISSION TECHNOLOGYIn FTTH systems providing broadcasting services, theoptical signal for video is amplified and distributed by
optical amplifier. As was noted above, the higher the output power of the optical amplifier the more it is possible toincrease the distribution efficiency of the FTTH system.
The erbium-doped fiber amplifiers (EDFAs) used in existing FTTH systems are limited by the output of the pumping lasers, with a maximum signal output power of about+22 dBmW. Since to achieve higher output it is necessary
to increase the number of pumping lasers, there was a
resulting problem that it became more expensive andmore bulky.
With the FITELwave OA-PLUS series of high-power
multiport optical amplifiers, utilizing the technology of ourclad pump optical amplifier 3), 4), Furukawa Electric hassolved this problem. Figure 2 shows the clad pump optical amplifier gain-block, and Figure 3 is a photographshowing a high-power multiport optical amplifier. With thisamp, the maximum output of the amplifier gain-block is+33 dBmW, making it possible to obtain an optical output
after splitting of +20 dBm x 16 ports. This device is of unit
configuration for each 16 ports (MAX: 32 ports), accommodating a maximum of 64 ports (MAX: 128 ports) in a
5U size chassis. This is a standard sort of system design,
capable of providing coverage to approximately 4000
households. Because this kind of multiport optical amp isof higher density it presents difficulties with respect toheat dissipation, but by revamping the electrical circuitry

Figure 2Figure 3

High-power multiport optical amplify for CATV.

High-power multiport optical amplifier (FITELwave
OA-PLUS series).

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Furukawa Electric Broadband Involvement in FTTH Systems

and repeated simulation and experimentation with theheat dissipation mechanism, it has been possible to arriveat an optimal heat dissipation structure. It was also possible to effect a significant reduction in power consumption,
resulting in the design of an optical amplifier that is optimal for configuring FTTH systems. Redundancy is provided for all power supplies and fans, and the structure
allows for hot swapping. A simple network management
protocol (SNMP) and web browser monitor are standard
equipment for improved operating convenience. In addition to this series of optical amplifiers, we have also developed the FITELwave OA-BASE series of multi-port opticalamplifiers, which does not adopt unit construction and iseasier to use in comparatively mid-sized FTTH systems,
and the FITELwave 4200 series of 1U-size pizza-box typeoptical amplifiers, which can be used in relaying applications, etc. (see Figures 4 and 5).

4.

GE-PON TECHNOLOGYFor FTTH systems that provide data transmission, gigabit
Ethernet passive optical network (GE-PON) technology isused, providing 1 Gb/s data speeds to multiple subscribers. This standard was established in 2004 as IEEE802.3
ah 1000 BASE-PX, offering a protocol that features a highdegree of Ethernet affinity. It uses the 1490 nm band forthe down wavelength and 1310 nm for up.
To achieve a commercially viable central station or optical line terminal (OLT) for GE-PON applications, Furukawa
Electric began with a proprietary effort to develop its key
component--the optical transceiver module. Figure 6
shows a transceiver module for a GE-PON OLT 5).

Figure 6

Figure 4

FITELwave OA-BASE series high-power multiport
optical amplifier.

Figure 5

FITELwave OA-4200 series high-power multiport
optical amplifier.

Figure 8

Figure 7

GE-PON OLT transceiver module.

GE-PON central station OLT (FITELwave AG1600E).

GE-PON management software (FITELwave AGmanager).

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Furukawa Electric Broadband Involvement in FTTH Systems

The OLT is 3 U size, and accommodates 16 PON interface (PIF) cards, to which can be connected a maximumof 64 receivers’ D-ONUs (see Figure 7). In the standard
design (budget loss is 29 dB), it supports connection ofup to 1024 subscribers’ D-ONUs. Redundancy is provided for all power supplies and fans, and the structure
allows for hot swapping. In addition to a line-up of dedicated management software (FITELwave AGmanager)that simplifies setting, status monitoring and history
retrieval for OLT and D-ONUs, and is also capable ofbatch management of multiple OLTs and D-ONUs, a simple network management protocol function is also provided. Figure 8 shows the conceptual image of the software.
For its part the D-ONU is of compact, lightweight
design, and has a receptacle for holding excess fiber
length (see Figure 9). It has two LAN ports, with independent settings for quality of service (QoS), allowing, forexample, port 1 to be operated to optimize Internet connectivity while port 2 operates at a constant bit rate (CBR).
GE-PON service range is up to a maximum of 20 km,
and the maximum number of branches is 64. Businesses
providing FTTH services often desire non-standard usage
modes, such as providing service at a distance or further
improving fiber use efficiency. And by converting the several wavelengths of the GE-PON OLT PIF card, we havealso developed a GE-PON extender (FITELwave AG400),
with four different PON lines multiplexed on a single fiber(see Figure 10). The use of this device allows up to 256
D-ONUs to be connected by a single fiber, and can
extend the service range to a maximum of 50 km.

5.

WDM TECHNOLOGY

using at this point in the introduction of FTTH systemsinvolves planar lightwave circuit (PLC) technology that wehave developed in house 6), 7). Figure 11 shows the module.
PLC technology lends itself very well to mass production, and is the technology adopted for multiport optical
couplers and the like. The WDM filter developed by FITEL
makes use of these PLC technologies, and is characterized by having WDM filters for eight lines accommodated
in a single module. In this way it has been possible tosimplify the design of optical WDM filters for central offices. Figure 12 shows WDM filter assemblies for a centraloffice. The WDM filters for the terminal side are normallyinstalled in the subscriber’s terminal, but in addition tosuch standard products, Furukawa Electric has developed a product which accommodates WDM filters foreight subscribers and eight multiport couplers in a module that can be installed in a drop closure, and also offers
an array of solutions that can significantly reduce the cost
per subscriber. Figure 13 shows a view.

Figure 11 Triple-play WDM filter array module using FITEL’s
PLC technology for central offices.

In FTTH systems the optical signals for broadcasting andthe optical signals for data transmission are in somecases multiplexed for transmission.
A number of technologies have be investigated withrespect to WDM filters, but the method that we are actively

Figure 12 Triple-play WDM filter assembly unit for central offices.

Figure 9GE-PON D-ONU (FITELwave AG20E).

Figure 10 GE-PON extender using WDM (FITELwave AG400).

Figure 13 All-in-one PLC module (integrated optical splitterand WDM filters) installed in a drop closure installednear subscribers.

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6.

CONCLUSION

We have presented an overview of FTTH systems and ofFurukawa Electric’s involvement with them. The productsthat Furukawa Electric has developed in this area are allbased on key components researched at the FITEL
Photonics Laboratories and Yokohama ResearchLaboratory, and components developed at Ofs. We will bemost gratified if reference to this paper is helpful in developing products required in FTTH systems.

REFERENCES
1) Shinoda et al.: Development of 50-Channel Optical FM-FDM Video
Distribution System, Furukawa Electric Review, No. 91, 1992. (inJapanese)2) Tomita et al.: Long-distance Transmission Experiment ofTerrestrial Digital Broadcasting Utilizing Gifu Information Super
Highway, Proceedings of The Institute of Image Information andTelevision Engineers, Vol. 28, No. 60, pp.1~4. BST2004-105 (Oct.
2004). (in Japanese)3) Cladding-Pumped Optical Fiber Amplifier, Furukawa Review,No.26, September 2004.
4) High-Power Multiport Optical Amplifier for CATV, Furukawa
Review, No. 31, February 2007.
5) Iwase et al.: Optical Transceiver Modules for Gigabit Ethernet PON
FTTH System, Furukawa Review, No. 28, August 2005.
6) Ono et al.: PLC Products for FTTH Systems, Furukawa Review,No. 26, September 2004.
7) Nara et al.: PLC-MZI-type 3-Wavelength Wideband WDM Filter
Array for FTTH Video Distribution Services, Furukawa Review,No. 28, August 2005.

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