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Super Low-Loss Multifiber Optical Connector

1.

INTRODUCTION

MT connectors, which are representative of multifiber optical connectors have been used for a wide range of uses,
including application products. Compared to single-fiber
optical connectors, however, in which optical alignment isachieved for one fiber, there were technical difficulties in
reducing insertion-loss, and about 0.3 dB was considered
the limit. In the optical connector developed here, we havecompletely reduced the error factor attributable to theamount of optical fiber position that leads to insertion-loss,
and have realized a maximum insertion-loss value of 0.15
dB or less, equivalent to a single-fiber optical connector.
The accuracy of ferrule fabrication was also improved by ahigh-precision molding technique using an epoxy resin.
Loss values equivalent to or better than that of single-fiber
optical connectors having been realized, transmission
equipment using 8-fiber and 12-fiber configurations can bedealt with collectively, bringing significant improvements inoperation, mounting efficiency, and mounting density.

2.

FEATURESThis time, our company realized the performance of super
low-loss by MPO connector and LIGHTRAY MPX TM connector of 8-fiber. Photo 1 shows the super low-loss 8-fiber
MPO connector. The key technique for achieving super
low-loss is in improving MT ferrule precision. Although
Furukawa Electric has long used MT connector molding
techniques of a sub-micron order, aiming at improved performance, it has in this program further developed thesetechniques to reduce insertion loss, specifically,1) ferrule structure, and2) improvement in mold precision.
In terms of ferrule structure, we have modified the sizeand position of the window used for adhesive injection, forthe purpose of preventing deformation of the ferrule. To
reduce the amount of positional error of the optical fiber,
the size of guide holes and fiber holes was reexamined,
and with respect to the amount of change of position error
produced by the slide of the end-face, which is a charac-† LIGHTRAY MPX TM is a registered trademark of Tyco
Corporation.

teristic problem in connectors that have oblique end-face,
it was so arranged that a slide might be suppressed.
In terms of improvement in mold precision, we improved
the mold design to secure the straightness of the fiber
holes in order to reduce their position error changing in
the depth direction. The degree to which the fiber tip is
polished in becomes large when angled polishing isapplied to the end-face as in MPO connectors. If theamount of position error of the fiber hole changes in thedepth direction, any increase in the amount of polishingwill change the amount of position error of the fiber.
Accordingly the error factors were thoroughly eliminated
so that the amount of position error of the fiber would notdepend on the amount of polishing, and a satisfactory
result was obtained.

3.

INSERTION LOSS CHARACTERISTICIn random connections, a maximum of 0.15 dB and anaverage of 0.065 dB was realized. Figure 1 shows theinsertion-loss distribution. A reduction of -0.15 dB wasattained in the maximum loss in comparison to a maximum of 0.30 dB and an average of 0.097 dB in the conventional low-loss type. These values are also supportedby the improvement in end-face polishing technique, andare obtained by using a dry connection. Figure 2 shows
the insertion-loss distribution in a conventional low-loss
MPO8 connector. In reducing insertion-loss, improvementof polishing technique to increase the outer diameter

Photo 1Super low-loss MPO8 optical connector.

Furukawa Review, No. 23

2003

121

Super Low-Loss Multifiber Optical Connector

accuracy of the optical fiber and reduce core eccentricity,and physical contact are indispensable, in addition toimprovements in ferrule accuracy.
It was confirmed that the insertion-loss distribution
shown in Figure 1 indicates performance that is completely equal to that of the insertion-loss distribution for a single-fiber optical connector shown in Figure 3.

300

Frequency

250

minimum 0.00dB
maximum 0.15dB

200
150

mean0.065dB

s.d.

0.0298dB

10050
00.00

0.10

0.20

0.30

0.40

0.50

4.

CONCLUSION

Insertion loss (dB)Figure 1

Insertion loss distribution for super low-loss MPO8.

1200Frequency

1000

minimum 0.00dB
maximum 0.30dB

800
600

mean0.097dB

s.d.

0.0580dB

400
200
00.00

0.10

0.20

0.30

0.40

0.50

By developing a multifiber optical connector with characteristics more than equivalent to single-fiber connectors, afull lineup of product such as an optical cord with a multifiber optical connector can be realized, satisfying the needto diversify transmission equipment as in optical paralleltransmission etc. To support reducing total insertion-loss,
Furukawa Electric is focusing on supplying optical cords
with multifiber connector, not only ferrules alone.
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)Figure 2

Insertion loss distribution for conventional low-loss
MPO8.

100
minimum 0.03dB

Frequency

80

maximum 0.28dB

60

mean

0.088dBs.d.

0.0460dB

40

20

00.00

0.10

0.20

0.30

0.40

0.50

Insertion loss (dB)Figure 3

Insertion loss distribution for single-fiber connector.

Furukawa Review, No. 232003122