Optical communication device

Details Optical communication device Optical communication device

2003-05-06

2004-11-09

Mayo, III, William H. (Department: 2831)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

Reexamination Certificate

active

06814504

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical communication device (LD module, PD module, LD/PD module) for transmitting and receiving multichannel signals by M-channel ribbonfibers (tapefibers) which contain M element fibers, where M is the number of channels. The pitch of multichannel fibers has been determined to be 250 &mgr;m. Optoelectronic device chips, laser diodes or photodiodes, are squares of a side from 600 &mgr;m to 300 &mgr;m.
Sizes of optoelectronic devices are larger than the pitch of the multichannel fibers. Size discrepancy inhibits optical communication modules from installing M optoelectronic devices on straight line extensions of the M element fibers of the M-channel ribbonfibers.
This application claims the priority of Japanese Patent Application No.2002-153870 filed on May 28, 2002, which is incorporated herein by reference.
2. Description of Related Art
FIG. 5
shows an MT connector of a standard type of a four channel connector. A resin-made MT male connector
52
has a pair of guidepins
54
and
54
projecting from the front. The MT connector
52
contains a front end of a four-core ribbon fiber
56
. The four-channel ribbonfiber
56
includes four optical fibers FBa, FBb, FBc and FBd. The standardized fiber pitch P
1
of the ribbonfiber is 250 &mgr;m (0.25 mm). Four ends of the fibers appear on the front surface.
Another resin-made MT female connector
53
has a pair of guideholes
55
and
55
for joining to the above male connector
52
. The MT connector
53
contains a four channel ribbonfiber
56
including four element fibers. Both connectors are combined or separated by the guidepins and holes. When the connectors
52
and
53
are coupled with each other by inserting the guidepins into the guideholes, each end of the element fibers of the connector faces an end of a counterpart fiber of another connector. The MT connector is one of low-cost, small-sized, prevalent connectors. The fiber pitch P
1
is 250 &mgr;m. Laser diode chips or photodiode chips are squares or rectangles of a side of 600 &mgr;m to 300 &mgr;m. It is impossible for a multichannel fiber to join laser diodes or photodiodes to the element fibers with keeping the pitch P
1
.
{circle around (
1
)} M. Shishikura, K. Nagatsuma, T. Ido, M. Tokuda, K. Nakahara, E. Nomoto, K. Sudoh and H. Sano, “10 Gbps×4-channel parallel LD module”, Proceeding of the 2001 IEICE, C-3-50, p160
FIG. 6
shows a perspective view of a 10 Gbps four channel LD module with enlarging lightwaveguides proposed by {circle around (
1
)}. The LD module is made on a silicon bench
57
by piling a SiO
2
lightwaveguide layer on the silicon bench, producing four width enlarging lightwaveguides Wa, Wb, Wc and Wd having a 250 &mgr;m initial pitch and a 1000 &mgr;m final pitch and installing four laser diodes LDa, LDb LDc and LDd at final ends of the lightwaveguides at a 1000 &mgr;m pitch.
The initial pitch P
1
of the lightwaveguides Wa, Wb, Wc and Wd is 250 &mgr;m for coinciding with the pitch of multichannel ribbon fibers which contain M element fibers at a 250 &mgr;m pitch. The initial 250 &mgr;m pitch allows the ribbonfiber to adhere to a front end of the lightwaveguides permanently. The final 1000 &mgr;m pitch allows individual laser diodes LDa, LDb, LDc and LDd to align at ends of lightpaths with sufficient margins. Smooth curvatures enlarge a width of the lightpaths continuously from the 250 &mgr;m pitch to the 1000 &mgr;m pitch on the silicon bench.
Parallel arrangement of a plurality of laser diode chips of a square from 600 &mgr;m to 300 &mgr;m requires a wide pitch more than 500 &mgr;m for the sake of thermal diffusion and a chip installment space. A wide pitch more than 1000 &mgr;m is preferable for depressing mutual crosstalk. The known reference {circle around (
1
)} enlarges the pitch of lightwaveguides continuously in the lateral direction along the lightpaths for solving the problem of the pitch discrepancy and the crosstalk.
The pitch P
1
of multichannel fibers is different from a pitch P
2
for aligning a plurality of lasers or photodiodes on a bench of a surface-mounting type module. A channel pitch should be enlarged midway on lightpaths from a ribbonfiber to a multichannel optical communication module. It is a good contrivance of enlarging the channel pitch by making curving lightwaveguides on a silicon bench like the known reference {circle around (
1
)}. However, it is difficult to produce the curving lightwaveguides on the silicon bench with high preciseness. Moderate curvature of a lightwaveguide requires a large length of the silicon bench. Alignment of lasers or photodiodes with lightwaveguides is a difficult step, which raises the cost of modules. A long silicon bench and built-in curving lightwaveguides enhance the cost since P
1
and P
2
have a difference.
One purpose of the present invention is to provide an optical communication device which enlarges the multichannel pitch without using of the high-cost curving lightwaveguides. Another purpose of the present invention is to provide a device which alleviates the length of the silicon bench. A further purpose is to provide a device which dispenses with a time-consuming alignment step for joining fibers to bench-built in lightwaveguides. A further purpose is to provide a device which can easily be attached to or detached from a prevalent multichannel MT connector.
The present invention proposes a communication device containing a connector having a pair of guidepins or guideholes, maintaining ends of a channel number of parallel optical fibers having tails extending from a rear wall, a bench (e.g., silicon bench) having M (M=channel number) parallel V-grooves aligning at a pitch P
2
wider than a pitch P
1
at a forward part, M linear lightwaveguides aligning at P
2
and following the V-grooves and laser diodes or photodiodes mounted at ends of the lightwaveguides and a package including leadpins for supporting the connector, the fibers and the bench. The width of neighboring fibers is enlarged from P
1
to P
2
at an enlarging space ES between the connector and the silicon bench.
The discrepancy of the pitches P
1
and P
2
requires a pitch conversion element between the connector and the lasers or photodiodes. The present invention allows the optical fibers to bend freely at the enlarging space ES for converging the pitch instead of built-in lightwaveguides. Lightpaths align at P
1
in the connector but align at P
2
on the bench. The present invention enlarges the pitch by freely bending the fibers at the free space ES from the P
1
pitch to the P
2
pitch. The optical fibers curve with a locus consisting of two reciprocal arcs. The joint of two arcs is a neutral point without curvature. An elastic fiber yields optimum curvature in a freestanding state. Formation of curvatures in a free space enjoys high degree of freedom unlike formation of lightwaveguides on a silicon bench. It is easy to bend thin, elastic fibers in the free space.
The pitch-conversion portion (ES) exists out of the silicon bench in the device of the present invention. The bench does not contain the pitch conversion portion. The silicon bench should have parallel straight lightwaveguides and parallel straight V-grooves in the longitudinal direction. The silicon bench is immune from curved lines. A plurality of silicon benches can be made upon a silicon wafer by wafer process at a stroke.
The pitch-conversion should be done in a space in a package(case) but out of the (silicon) bench. The package should contain fiber pitch-expanding region. The fiber pitch-extending region may be a free space for allowing the pitch to extend in a free state. Since the fibers are held by the connector and the bench at both ends, the fibers bend into natural curvatures in the free state. The fibers are later fixed with a resin in the package. The curving portions are sustained by the resin stably without vibration in the package.
Alternatively, V-grooves can be prepared in the pitch-extending region in an inner case for guiding

Affiliated with

Also associated with

Rating

Optical communication device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical communication device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical communication device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3362873