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High-Power Multiport Optical Amplifier for CATV1.

INTRODUCTION

It is some time now since the convergence between telecommunications and broadcasting technologies has
been advocated, and, in line with this, the Triple Play
Service has been implemented and is expanding rapidly
which provides the three services of Internet access,video distribution and (optical) IP phone over a single
broadband connection using the FTTH (fiber to the home)or CATV. Reducing the cost per subscriber constitutes anabsolute requirement to make such a new service to proliferate. And increasing the output power of individual
optical amplifiers in the video distribution system is known
as an effective solution to this cost reduction requirement.
Accordingly, we have adopted a new technologicalapproach to develop a high-power multiport optical amplifier for video distribution using erbium/ytterbium (Er/Yb)
co-doped double-clad fiber and multi-mode pumping LD,
which is different from conventional optical amplifiers.

2.

FEATURES

3.

CHARACTERISTICS

Figures 2 and 3 show the wavelength dependence of the
optical output signal power per port at an optical inputpower of 0 dBm and that of the noise figure (NF), respectively. It can be seen that noise figure of 5.5 dB or less,equivalent to that of ordinary EDFAs, is achieved at anOutput signal power（dBm/port）

Figure 1 shows an appearance of the high-power multiport optical amplifier developed here. In its casing measuring 160 mm (L) x 121.5 mm (W) x 29.5 mm (H) excluding heat radiating fins, the amplifier integrates output control circuitry provided with communication functions andan output branching splitter, achieving amplification of-3-dBm input signal to an output signal power of +20
dBm x 16 ports, i.e. +33 dBm in total.
In terms of optical configuration, the amplifier adopts
two-stage configuration to minimally suppress noise deg-radation at the time of analog signal transmission. Its preamplifier stage realizes low noise by employing an erbium-doped fiber amplifier (EDFA) commonly used. And
the booster amplifier is a clad-pump amplifier, whereby anEr/Yb co-doped double-clad fiber is pumped by 980-nm
multimode pumping LDs, realizing low noise and highoutput power simultaneously. The Er/Yb co-doped double-clad fiber has a flower-shaped cross-section for its
cladding where pumping light propagates, enhancing theprobability with which the multimode pumping lightlaunched into can effect low-loss transmission in the core
where rare earth elements are doped.
The amplifier operates on a single DC +5-V power supply. A user-friendly interface using RS232 is provided toenable various settings and information collection, making external setting and modification also possible during
operation. Various output control modes are availableincluding automatic level control (ALC), automatic gaincontrol (AGC), automatic current control (ACC) and automatic pump power control (APC), and these mode selection can be changed as desired along with target setting.
Setting for various alarm functions related with operationof the optical amplifier is also supported, and a protection
function against loss of input power is provided.

2321191715
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119751520

1540

1560

1580

1600

Wavelength（nm）

Figure 1

Appearance of high-power multiport optical amplifierfor CATV.

Figure 2

Input signal wavelength dependence of optical signal output power (input signal power: 0 dBm).

Furukawa Review, No. 31

200721High-Power Multiport Optical Amplifier for CATV

input signal wavelength range of 1540~1560 nm.
Moreover, in the analog transmission characteristics evaluation using an external modulator for optical transmitter,
109NF（dB）

84.

76541520

it has been confirmed that both the composite second
order distortion (CSO) and composite triple beat distortion (CTB) satisfy an adequate level of -73 dB or less. Thepower consumption is about 40 W. Table 1 shows thebasic characteristics of the high-power multiport opticalamplifier developed here.

15401560

1580

1600

Wavelength（nm）

Figure 3

Input signal wavelength dependence of noise figure(input signal power: 0 dBm).

Table 1

Specifications of high-power multiport optical amplifier.
Item

Specification

Wavelength

1540〜1560 nm

Input signal power-3〜+10 dBm

Output signal power per port≧+20 dBm/port

Output power uniformity
Noise figure
Polarization dependent gain

≦1.0 dB≦5.5 dB @Pin=0 dBm,
1550 nm≦0.5 dB

Power supply voltageSingle, DC +5 V

Power consumption≦40 W @Pout≧+20 dBm/port

CONCLUSION

A high-power multiport optical amplifier for video distribution has been developed aimed at the FTTH market.
Despite its compact size and low power consumption of
40 W, the amplifier has achieved an output signal powerof +20 dBm x 16 ports, i.e. +33 dBm in total, unattainablewith conventional EDFAs, using erbium/ytterbium codoped double-clad fiber and multi-mode pumping LDs.
The optical amplification technology for high output poweris expected to be applied not only in the FTTH market but
also in various fields.
For more information, please contact:
For technical issues,
Optical Components Department,
Telecommunications Company
TEL: +81-436-42-1703
FAX: +81-436-42-1789
For general issues,
Planning and Coordination Department,
Telecommunications Company
TEL: +81-3-3286-3427
FAX: +81-3-3286-3708
E-mail: fitel@ho.furukawa.co.jp

Furukawa Review, No. 31

200722