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High-Precision Dual-Core Ferrule

1.

INTRODUCTION

The 2-fiber ferrule is a key element in DWDM optical modules. Although 2-fiber ferrules made of zirconia ceramics
have been widely used for some time, high-precision dualcore ferrules made of resin have been developed byFurukawa Electric. They are more easily mass-produced
and therefore realize cost reductions. Precision molding
techniques using the epoxy resin that has a proven trackrecord in MT ferrules have made possible an attractive
product offering numerous features.
In the following we describe the features of this highprecision dual-core ferrule, as well as an example of a
product in which it may be used.

2.

FEATURES

Compact size, low insertion-loss, high reliability and low
price are essential in the optical modules used in DWDM
systems. The high-precision dual-core ferrule developedby Furukawa Electric on the basis of extending the precision molding and material techniques used for MT ferrules, offers the following features.
• High reliability, easy mass-producibility and low costare compatible thanks to the use of epoxy resin thathas a proven track record in MT ferrules.
• The fiber arrangement pitch can be designed freely
taking advantage of the feature of resin molding, suchas narrow pitch or wide pitch including not only 250µm, in compliance with dimensions demanded fromoptical modules.
• Miniaturization of optical modules is especially advantageous in areas where a narrow pitch such as 0.127
mm is characteristic.
• High reliability to temperature change, humidity, etc.
• Selection of material for the outside sleeve is free. For
example, when carrying out direct YAG welding at amodule, the material appropriate for the purposes,
such as SUS304, can be chosen. And since a simple
cylindrical shape is used, the outside sleeve is easily
machined and the required size accuracy is also easily achieved. Photo 1 shows a typical high-precisiondual-core ferrule. Small size and narrow pitch arerealized, with a full length of 9 mm, outer diameter of
1.8 mm, and pitch between fibers of 0.127 mm.

3.

APPLICATIONSApplications of this high-precision dual-core ferrule include
2-fiber collimators, pumping modules, optical circulators,
optical switches, and so on. In the following we focus on
an optical multiplexing module (WDM combiner) for a
Raman amplifier as a product in which the high-precisiondual-core ferrule may be used. Figure 1 shows the structure of a WDM combiner for a Raman amplifier. Light oftwo different wavelengths is combined at the common port
by a combination of a dual-core ferrule and LWPF.
The depth direction change of the pitch between the twofibers, the fiber hole pitch, fiber hole accuracy, etc. areessential parameters for making this configuration lowloss. Each parameter can be easily optimized by producing the dual-core ferrule by resin molding. Compared to aconventional WDM combiner, the reduction in loss realized was significant: 0.3dB or less (see Figure 2).
Moreover, in terms of high power tolerance, it was confirmed that the characteristic stabilized at 3 W for 2000 hand 3 W + 3 W for 500 h, and showed high reliability.
Figure 3 shows the results of a test at 3 W + 3 W for 500h.

Whole view

Photo 1

End-face

Typical high-precision dual-core ferule.

Dual-core ferrule

WDM filter
Fiber

Figure 1

Structure of wavelength combiner.

Furukawa Review, No. 23

2003

119

High-Precision Dual-Core Ferrule

IL Distribution of WDM Module(Pass-Common port)

4.

CONCLUSION

150

The high-precision dual-core ferrule developed in thiswork is applicable to various needs for the optical devices
indispensable to DWDM systems, and particularly the 2fiber collimator. Construction of DWDM systems with highflexibility is achieved at low cost by employing the featuresof this product to maximum effect.

Frequency

125
mean: 0.26 dB
s.d.: 0.06 dB

100755025
0<0.1<0.2<0.3<0.4<0.5<0.6<0.7<0.8

For more information, please contact:
Assembly Production Engineering Sec., Interconnect
Components Dept., FITEL Interconnectivity Div.
TEL: +81-436-42-1674
FAX: +81-436-42-9355

Insertion Loss (dB)IL Distribution of WDM Module(Reflect-Common port)
150

Frequency

125
mean: 0.27 dB
s.d.: 0.07 dB

100
75
50
25
0<0.1

<0.2<0.3<0.4<0.5<0.6

<0.7

<0.8

Insertion Loss (dB)Figure 2Insertion loss characteristics.

Insertion Loss Change (dB)

3W+3W High-Power Test Result
0.3
0.2
0.1
0-0.1
-0.2
-0.3
-0.4
0100

200300400500Time (hrs)

Figure 3

3 W + 3 W high power test result.

Furukawa Review, No. 23

2003120