2001 Fiscal Year Final Research Report Summary
Development of an optical system for perfect coupling in the DWDM optical communication system
| Project/Area Number |
12555095
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
電子デバイス・機器工学
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| Research Institution | Utsunomiya University |
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Principal Investigator |
SHIRAISHI Kazuo Utsunomiya Univ., Faculty of Engineering, Professor, 工学部, 教授 (90134056)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Toshimichi Namiki Quanta Optic Technologies, Section Leader, オプト商品グループ, 設計セクションリーダー
YODA Hidehiko Utsunomiya Univ., Faculty of Eng., Research Associate, 工学部, 助手 (30312862)
MATSUMURA Kazuhito Utsunomiya Univ., Faculty of Eng., Professor, 工学部, 教授 (70005297)
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| Project Period (FY) |
2000 – 2001
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| Keywords | optical fiber / field distribution / GI fiber / lensed fiber / optical communication / laser diode / graded index |
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| Research Abstract |
This research has successfully finished. We aimed the development of optical system for perfect coupling between pumping laser diodes (LDs) and receiving optical fibers in the DWDM system, and achieved the aim by using wedge-shaped graded-index (GI) lensed fibers. In this research we evaluated the optical radiation characteristics of high-power semiconductor LDs at first. Next, we designed and produced (1) wedge-shaped GI lensed fibers and (2) cascade-type wedge-shaped GI lensed fibers. As a result, the wedge-shaped GI fibers succeeded in improving the coupling coefficient between LDs and fibers compared with conventional techniques. Following are summaries of the results.
1. Development of wedge-shaped GI fibers
High-power semiconductor LDs for pumping EDFAs are designed to emit elliptical modal fields at their endface with high aspect ratio from 2 over 40. In addition, they tend to have large astigmatism of over 100 μm. As the aspect ratio is higher, the coupling losses between these L
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Ds and receiving optical single-mode fibers become larger using conventional lensed fibers. We propose a new lensed fiber employing a wedge-shaped GI fiber, of which the coupling loss is estimated to be 2.5 dB. We fabricated the proposed fiber and investigated its coupling loss characteristic, but the coupling loss was 5.8 dB. Because some differences between designed structural parameters of the fiber and measured ones exist.
2. Development of cascaded-type wedge-shaped GI fibers
In order to improve the not small coupling loss of 5.8 dB, we proposed a new fiber employing two cascaded GI fiber chips with a wedge-shaped end. The cascade-type wedge-shaped GI fiber achieves high-efficiency coupling with LDs even if the LDs have large astigmatism. We fabricated the proposed fibers for the LD with an aspect ratio at the endface of 42 and astigmatism of 176 μm. We experimentally confirmed that the proposed lensed fiber had a low coupling loss of 2.5 dB and a long working distance of 67 μm. We also investigated the tolerance characteristics for various displacements. Less
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