TP（技術資料）

高出力光増幅器に関する一般情報（General information for high power optical amplifier）

OITDA/TP 26/AM：2017
第1版

公表 2017 年 3 月

取纏委員会
光増幅器標準化部会

発行：一般財団法人光産業技術振興協会
Optoelectronics Industry and Technology Development Association（JAPAN）

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CONTENTSINTRODUCTION....................................................................................................................................... (3)1

Scope ...................................................................................................................................................... 1

2

Normative references............................................................................................................................ 1

3

Terms, definitions, and abbreviated terms ......................................................................................... 1

4

3.1

Terms and definitions .................................................................................................................... 1

3.2

Abbreviated terms ......................................................................................................................... 1

Configuration ........................................................................................................................................ 2
4.1

EDFAs using combined single mode pump laser diode ............................................................... 2

4.2

Cladding pumped fiber amplifier.................................................................................................. 3

4.2.1

General .................................................................................................................................... 3

4.2.2

Cladding pump methodology ................................................................................................. 4

4.3

EDFA by using cascaded Raman resonator ................................................................................. 8

5

Test method ........................................................................................................................................... 8

6

Considerations on a high power optical amplifiers ............................................................................ 9
6.1

Designing consideration ................................................................................................................ 9

6.2

Handling considerationn ............................................................................................................... 9Annex A (informative)

Application of high power OAs ....................................................................... 10

A.1

General ......................................................................................................................................... 10A.2

Power amplifier for FTTH PON systems ................................................................................... 10

A.3

Ultra-long haul DWDM transport system ................................................................................. 10

Annex B (informative)

IEC documents on high optical power .............................................................. 11

Bibliography ............................................................................................................................................... 12
Figure 1 – Schematic diagram of the EDFA using combined single mode pump laser diode ......... 3
Figure 2 – Output characteristics of high-power EDFA .................................................................... 3
Figure 3 – Schematic diagram of the cladding pumped fiber amplifier ........................................... 4
Figure 4 – Schematic of cladding pump .............................................................................................. 4
Figure 5 – Schematic structure of fiber bundle for power combiner................................................. 5
Figure 6 – V-groove side pumping arrangement ................................................................................ 5
Figure 7 – Schematic diagram of the section of Double cladding fiber ............................................. 6
Figure 8 – Cross section of the hole assisted double cladding fiber .................................................. 6
Figure 9 – Typical optical output power vs. drive current on 9xx nm multimode pump laser
module. .......................................................................................................................................... 7
Figure 10 – Configuration of double cladding amplifier .................................................................... 7
Figure 11 – Typical power conversion efficiency of double cladding amplifier ................................. 8
Figure 12 –Schematic diagram of the EDFA by using cascaded Raman resonator ......................... 8
Figure 13 –Test setup to measure optical output and gain ............................................................... 9（1）

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Figure A.1 – Schematic diagram of the FTTH system adapted high power OA ............................ 10（2）

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INTRODUCTION
Optical amplifiers (OAs) are necessary components as booster, line and pre-amplifiers for current
optical network systems. IEC TC86/SC86C, therefore, has published many standards for OAs.
Recently, high optical output power amplifier is used for applications in Passive optical network(PON) system and CATV systems.
Although OAs with high optical power which has more than 500 mW are deployed in field, there arevery few documents addressing high optical power.
This technical report provides a better understanding of high power amplifier, especially based on
cladding pump technology as well as concerning on handling high optical power.
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この技術資料に関して，ご意見・情報がありましたら，下記連絡先にお寄せください。
連絡先：一般財団法人光産業技術振興協会標準化室（3）

OITDA/TP（技術資料）

OITDA/TP 26/AM：2017

高出力光増幅器に関する一般情報
General information for high power optical amplifier

1 ScopeThis technical paper deals with high power optical amplifier. The main purpose of the report is toprovide general information relating to high power optical amplifier, which has high power output
over 500 mW. The report covers the following aspects:–

General information;–

Cladding pump technology;–

Test method for optical output and gain.

2 Normative references
There are no normative references in this document.

3 Terms, definitions, and abbreviated terms
3.1

Terms and definitions

No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:•

IEC Electropedia: available at http://www.electropedia.org/•

ISO Online browsing platform: available at http://www.iso.org/obp

3.2

Abbreviated terms

For the purposes of this document, the abbreviated terms given in IEC 61291-1 and the following
apply.
ASE

Amplified spontaneous emission

CO

Central officeDC

Double cladding

DWDM

Dense wavelength division multiplexing

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EDF

Erbium-doped fiber

EDFA

Erbium-doped fiber amplifier

FTTH

Fiber to the home

HP-EDFA

High power erbium-doped fiber amplifier

MLFL

Mode-locked fiber laser

MM

Multi-mode

MUX

Multiplexer

NA

Numerical aperture

OA

Optical amplifier

OFA

Optical fiber amplifier

OLT

Optical line termination

ONU

Optical network unit

OSNR

Optical signal-to-noise ratio

PCE

Power conversion efficiency

PON

Passive optical network

SM

Single-modeTV

Television

V-OLTVideo optical line termination

V-ONU

Video optical network unit

WDM

Wavelength division multiplexing

4 Configuration
4.1

EDFAs using combined single mode pump laser diodeFigure 1 shows the example of the schematic diagram of the Erbium Doped Fiber Amplifier (EDFA)
by applying multiple single mode pump laser. Amplifying erbium doped fiber by high output powerradiation which is multiplexed a plurality of single mode pump lasers around 1 480 nm which is
widely used allow to obtain high output power.

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EDF
Isolator

WDM

EDF
Isolator

WDM

MUX

MUX

Single mode
980nm Pump laser

Isolator

WDM

…

…

14xx nm Pumplaser

14xx nm Pump
laser

Figure 1 – Schematic diagram of the EDFA using combined single mode pump laser diodeFigure 2 shows the example of the output characteristics of high-power EDFA.

Figure 2 – Output characteristics of high-power EDFA
Polarization combine methodology is also applicable to realize more high output power.
4.2
4.2.1

Cladding pumped fiber amplifier
GeneralFigure 3 shows the schematic diagram of the cladding pump fiber amplifier. In this example,
conventional EDFA is used as pre-amplifier because the gain of cladding pump fiber amplifier isless than that of EDFA and the relatively high input power is required to obtain the high output
power.

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Er (Er/Yb) doped cladding
pump fiber

EDF
Isolator

WDM

Isolator

Single mode
980nm Pump
laser

WDM
(Powercombiner)

Isolator

Multimode
980nm Pump
laser

Figure 3 – Schematic diagram of the cladding pumped fiber amplifier

4.2.2
4.2.2.1

Cladding pump methodology
GeneralCladding pump methodology is the pumping technology by using multi-layer fiber composed of theinner cladding around the rare earth element doped fiber core for signal transmitting, which issurrounded by an outer cladding of lower refractive index. Large area of inner cladding enables to
input high power pump light from multi-mode pump laser which has higher electrical efficiency thansingle mode pump laser.
As Figure 4, light launched into the inner cladding also gets into the fiber core, where it can beabsorbed by laser-active ions. (Note that the inner cladding is undoped, so there is no pumpabsorption there.) Only, the overlap of pump light with the doped core is reduced, as much of thepump power travels in the undoped inner cladding.

Core
Inner cladding
Outer cladding

Figure 4 – Schematic of cladding pump

4.2.2.2

Pumping methoda) End-pumping
The pump light is launched into the end of the fiber as the same as EDFA using a conventional
single mode EDF.
b) Fused bundled fiber pump combiner

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In this method, several multi-mode fibers are bundled together, fused and drawn into a taper,
fusion spliced to a double cladding (DC) fiber, and then recoated with a low index polymer. Figure
5 shows one of the examples.

Figure 5 – Schematic structure of fiber bundle for power combinerc) V-groove side pumping
In this approach, the double cladding fiber is stripped and bonded to a glass slide; a V-shaped
notch is cut into the inner cladding, and the pump beam is launched by total internal reflection fromthe facet of the V-groove as Figure 6.

Figure 6 – V-groove side pumping arrangement

4.2.2.3

Key componentsa) Active fiber
As gain medium of cladding pumped amplifier, double cladding fiber is applied. DC fiber is an
optical fiber with a structure consisting of three layers of optical material instead of the usual two.
Figure 7 shows the example of the DC fiber. The inner-most layer is called the core. It issurrounded by the inner cladding, which is surrounded by the outer cladding. The three layers are
made of materials with different refractive indices. The core is doped with active dopant material; itboth guides and amplifies the signal light. The inner cladding and core guide the pump light, which
provides the energy to amplify the signal in the core. The core has the highest refractive index andthe inner cladding has lower refractive index than the core andthe outer cladding has thelowest. In most cases the outer cladding is made of a polymer material rather than glass.

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Core
Inner cladding
Coating

Figure 7 – Schematic diagram of the section of Double cladding fiber
Figure 8 shows another example of double cladding fiber. Here, the inner cladding for pump laser
is supported by very thin struts in the air cladding, by which the pump light is captured. Such astructure can have a very high NA for the pump light, which relaxes the requirements for the pumpbeam quality.

Figure 8 – Cross section of the hole assisted double cladding fiber
Co-doping ytterbium ions into an erbium-doped core is frequently used technique in an active fiber
for a high-power amplifier. There are two advantages for an ytterbium co-doping. One isbroadening the 980-nm absorption band, which enables using multiple 9xx-nm pump lasers withdifferent lasing wavelengths so that the pump power is greatly increased. The other is preventing
erbium ions from forming clusters, which makes high-concentration erbium doping possible andsuppresses upconversion. An efficient energy transfer from ytterbium to erbium ions also makes
this technique convenient.
b) Power combiner
For pumping double cladding fiber, multiplex device to combine high power pump laser light into
signal light is necessary.
c) Pump laser diodeMultimode 9xx nm laser more than 6.0 W fiber pigtail output is commercial product and it is reliable
for use telecommunications application. Figure 9 shows the typical performance on uncooled
multimode 9xx nm laser diode.

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Output power (W)TP 26/AM：2017
8
6
4
2
0
0

2

4

6

8

Drive current (A)Figure 9 – Typical optical output power vs. drive current on 9xx nm multimode pump laser
module.

4.2.2.4

Configuration of cladding pumped amplifier

Figure 10 shows configuration of cladding pumped fiber amplifier to evaluate the power conversion
efficiency. Er and Yb co-doped double cladding fiber is utilized for gain medium and multiple
multimode 980 nm band laser diode is used for pumping.

Er/Yb Double cladding fiber
Pout+16dBm input

Multimode
nmLaser
LaserdiodeMultimode
980 nm9xx
band
diode
Figure 10 – Configuration of double cladding amplifier

4.2.2.5

Performance example

Figure 11 shows the power conversion efficiency of cladding pumped amplifier. Using multiple
pump lasers, output power increases up to 10 W is realized in commercial and power conversion
efficiency (PCE) of more than 30 % in cladding pump amplifier allow radiating more than 3 W.

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PCE of Er Yb co-doped DC fiber amplifier
0.4
0.35
0.3
PCE

0.25
0.2
1550nm0.15

1560nm
0.1
0.05
0
0

2000

4000

6000

8000

10000

12000

Pump power [mW]

Figure 11 – Typical power conversion efficiency of double cladding amplifier

4.3

EDFA by using cascaded Raman resonator

Figure 12 shows the schematic diagram of the EDFA by using the pump laser which is cascaded
Raman resonator. Multi-mode pump laser which is easy to realize high output power can beutilized for high power pump laser into Er-doped fiber.

Figure 12 –Schematic diagram of the EDFA by using cascaded Raman resonator

5 Test method
Figure 13 shows the example of test setup for high power amplifier to measure optical output andgain. Most of the high power optical amplifiers are designed power amplifier (booster amplifier),
therefore an optical input power is also required high power level (e.g. more than +13 dBm) tomeasure an amplifier parameter (Output power, Gain, Noise figure and so on). Since the optical

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output power for optical source in commercial is limited, manufacturers use amplified signal opticalsource by additional OA. To keep high accuracy of measurement, good OSNR (at least 35dB) in
input signal is recommended because the amplified spontaneous emission (ASE) from optional OA
is also amplified by OA under test. An Optical spectrum analyzer also should be applicable formeasurement equipment.

OpticalsourceOAdB

Polarization
controller

Optical Variable
Bandpass Opticalfilterattenuator

OA
OptionOpticalcoupler

Optical
Power
meter

J1

J2
OA

OA
under testdB

Optical
Power
meter

Optical
Opticalattenuator Bandpass
filterFigure 13 –Test setup to measure optical output and gain

6 Considerations on a high power optical amplifiers
6.1

Designing considerationa) Component selection
Insertion loss of component in a high power amplifier should be as lower as possible to avoid
unexpected damage or degradation by transmitting high optical power. In addition, it is importantto reduce reflection at the connection points and components to avoid unexpected oscillation leads
to fiber fuse phenomena.
b) Heat dissipation
As components transmitting a high optical power, the insertion loss causes fever leads todeterioration and damage, even if it is slight. It is necessary to consider enough heat dissipation
because it has been reported that the degradation of coating with light leaked from the part ofbended optical fiber.
c) Reliability qualification criteria
There is still no distinct standard document which defines the reliability of an amplifier and its
components transmitting high optical power and under discussion in IEC.
6.2

Handling consideration

Laser product which has high power optical output over 500 mW is categorized as Class 4 laser
product in IEC 60825-1 and safety to human eye and skin is concerned. Manufactures and users
should take safe into account.

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Annex A
(informative)
Application of high power OAs
A.1

GeneralIn fact, high power OAs, especially OFAs are widely deployed in commercial optical network
systems. In this annex, current applications of high power OFAs are briefly introduced.

A.2

Power amplifier for FTTH PON systems

Recently, FTTH has been deployed by PON system. A PON system utilizes a passive splitter thatsplits input one signal to broadcast signals to many users. This system reduces the cost of thesystem substantially by sharing one set of electronics.
1490 nm
PON-OLT

1310 nm

PON-OLT
1550 nmWDM

BranchingdevicePON-ONU
TX
RX

V-OLT

Voice
Data

WDM
High power OA

Branchingdevice
V-ONU
RX

Video

Figure A.1 – Schematic diagram of the FTTH system adapted high power OA
Figure A.1 shows the schematic diagram of the FTTH system adapted high power OA. Most FTTH
systems are so-called "triple play" systems providing voice (telephone), video (TV) and data
(Internet access.) To provide all three services over one fiber, signals are sent bi-directionally overa single fiber using several wavelengths of light. Downstream digital signals from the CO throughthe splitter to the home are sent at 1 490 nm. This signal carries both voice and data to the home.
Video signal broadcast separately using a 1 550 nm laser which amplified by OFA to supply
enough signal strength to overcome the loss of the optical splitter. Usage of high power OA allows
the system to reduce the number of amplifier and controller in CO and reduce the equipment cost.
Upstream digital signals for voice and data are sent back to the CO from the home using an
inexpensive 1 310 nm laser. WDM couplers separate the signals at both the home and the CO.

A.3

Ultra-long haul DWDM transport system

Increasing the number of channels on the transport system requires higher power OAs in recent
years. Especially, the high power OAs are deployed as booster to long span repeater-less links, forinstance, island to island, desert area, and oil platform.

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Annex B(informative)
IEC documents on high optical power

IEC/TR 62547, Guideline document for the measurement of high power damage sensitivity ofsingle mode fibre to bends and guidance for interpretation of results
IEC 61300-2-14, Fibre optic interconnecting devices and passive components - Basic test andmeasurement procedures - Part 2-14: Tests - Optical power handling and damage thresholdcharacterization
IEC/TR 62005-10, Fibre optic interconnecting devices and passive components - Reliability - Part
10: High Power Transmission Test of Passive Optical Components
IEC/TR 62627, Fibre optic interconnecting devices and passive components - Fibre optic
connector cleaning methods
IEC 60869-1, Fibre optic passive power control devices - Part 1: Generic specification
IEC 61753-056-2, Fibre optic interconnecting devices and passive components performancestandard - Part 056-2: Single mode fibre pigtailed style optical fuse for category C - Controlledenvironment
IEC 61753-057-2, Fibre optic interconnecting devices and passive components performancestandard - Part 057-2: Single mode fibre plug style optical fuse for category C - Controlledenvironment
IEC 61753-058-2, Fibre optic interconnecting devices and passive components performancestandard - Part 058-2: Single mode fibre pigtailed style optical limiter for category C - Controlledenvironment
IEC/TR 61292-4, Optical amplifiers - Part 4: Maximum permissible optical power for thedamage-free and safe use of optical amplifiers, including Raman amplifiers

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Bibliography
IEC 60825-1, Safety of laser products - Part 1: Equipment classification and requirements
IEC 61292-3, Part 3: Classification, characteristics, and applications of optical amplifiers.
Furukawa Review, No. 19. 2000
IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 39, NO. 4, APRIL 2003 529 A New Method
for Side Pumping of Double-Clad Fiber Sources Jeffrey P. Koplow, Sean W. Moore, and Dahv A. V.
KlinerD. J. DiGiovanni and A. J. Stentz, Tapered fiber bundles for coupling light into and out of
cladding-pumped fiber devices, U.S. Patent 5 864 644, Jan. 26, 1999.
Goldberg, L.; Koplow, J., "High power side-pumped Er/Yb doped fiber amplifier," Optical Fiber
Communication Conference, 1999, and the International Conference on Integrated Optics andOptical Fiber Communication. OFC/IOOC '99. Technical Digest, vol.2, no., pp.19,21 vol.2, 21-26
Feb. 1999
Frank Koch1, Bera Pálsdóttir, 30dBm Wideband Air-Clad EDFA Using Two Pump Lasers OFC
2008
A. Fujisaki, M. Yoshida, T. Hirooka and M. Nakazawa, "Generation of 10 W, 100 fs, 10 GHz pulse
train using high power EDFA-MOPA system with cascaded Raman pumping," 2015 Conference on
Lasers and Electro-Optics (CLEO), San Jose, CA, 2015, pp. 1-2.
Pump and signal combiners for fiber laser and amplifier design [pdf] OFS FITEL, LLC.
Available at:< http://fiber-optic-catalog.ofsoptics.com/asset/pump-signal-combiners.pdf > [Accessed 21 Feb
2017].

_____________

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OITDA/TP 26/AM：2017

高出力光増幅器に関する一般情報
解 説
この解説は，本体及び附属書に記載した事柄，並びにこれらに関連した事柄を説明するもので，技術資料（TP）の一部ではない。

1

制定の経緯
光増幅器は光ファイバ伝送システムにおいて不可欠な部品である。近年、PON システムならびに CATVシステムにおいて高光出力光増幅器が用いられている。実際に 500 mW を超える光出力の光増幅器が実用化されているが、高出力に関して規定する標準がほとんど存在していない。本技術資料は、高出力光増幅器、特にクラッド励起技術に関する一般情報のほかに、通常の光増幅器との差異を明確にし、高光出力を取り扱う上での注意事項について、光増幅器だけでなくその周辺技術についても高出力に対応する標準化を活性化する手助けとなるよう記載内容を配慮した。

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TP 26/AM：20172

原案作成部会
この技術資料（TP）は，次に示す原案作成部会において原案を作成し，審議・承認した。

光増幅器標準化部会
氏名
（議長）
（メンバ）

（オブザーバ）
（事務局）

山 田
植 村
小 野
小 島
清 水
鈴 木
高 橋
津 﨑
冨 田
三 浦
三 澤
水 本
八重樫
吉 田
渋 谷
森
増 田
中 野
綿 貫

誠
聖
浩 孝
学
祐 貴
裕 一
英 憲
哲 文
貴 裕
寿太郎
隆 二
哲 弥
浩 樹
実
隆
博 之
岳 夫
博 行
恒 夫

構成表
所属

大阪府立大学
経済産業省商務情報政策局
日本電信電話株式会社
横河メータ＆インスツルメンツ株式会社
一般財団法人日本規格協会
富士通株式会社
株式会社 KDDI 総合研究所
SEI オプティフロンティア株式会社
日本電気株式会社
Oplink Japan 合同会社
パナソニック システムネットワークス株式会社
東京工業大学
沖電気工業株式会社
近畿大学
NEC スペーステクノロジー株式会社
経済産業省産業技術環境局
一般財団法人光産業技術振興協会
一般財団法人光産業技術振興協会
一般財団法人光産業技術振興協会（執筆者 八重樫 浩樹，三浦 寿太郎）

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TP（技術資料）：
高出力光増幅器に関する一般情報（General information for high power optical amplifier）

TP 番号：OITDA/TP 26/AM：2017

第1版

第 1 版 公表日：2017 年 3 月 10 日

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