Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
2003-03-13
2004-12-28
Healy, Brian M. (Department: 2883)
Optical waveguides
With optical coupler
Particular coupling structure
C385S043000, C385S050000, C385S014000, C385S048000, C385S129000, C438S031000, C398S079000, C398S082000
Reexamination Certificate
active
06836600
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to optical transmission systems and, more specifically, to low insertion loss optical couplers.
BACKGROUND OF THE INVENTION
Optical couplers are optical transmission system components used to connect planar arrangements of waveguides. As shown in
FIG. 1
, a star coupler
100
(discussed in detail in U.S. Pat. No. 4,904,042, issued Feb. 27, 1990 to Dragone, and herein incorporated by reference) has a free space region
110
bounded by an input junction
102
for receiving incoming signal(s) from a plurality of individual input waveguides
106
and an output junction
104
for power splitting the input signal(s) and/or coupling portions of the signal(s) to a plurality of individual output waveguides
108
. Insertion loss (a reduction in the power of a signal propagating through the coupler
100
) typically occurs at the input junction
102
because of the abrupt change in the physical dimensions of the individual input waveguides as compared to the free space region
110
. The abrupt change causes a scattering of light associated with the signal, subsequently reducing power.
In a theoretically ideal coupler, waveguides approaching a free space region are nearly parallel to one another. The waveguides are shaped so that they are narrow at first and then increase in width until the gap between them is zero (a point which defines for example, the input junction). Zero gap width along with non-converging waveguides provides for a theoretical insertion loss of zero.
As shown in
FIG. 2
, the input junction
102
to the free space region
110
of conventional star coupler
100
is essentially arc-shaped. A first individual waveguide
106
1
and a second individual waveguide
106
2
are shown in detail as having respective uniform waveguide sections
202
and horn sections
204
. The uniform waveguide sections
202
have a substantially uniform waveguide width Wu. The horn sections
204
change to a different width Wt as they extend from the uniform waveguide sections
202
to the input junction
102
. The radial nature of the geometry of the individual waveguides along the input junction
102
forces them to converge too quickly for the transition to be gradual and thus truly have zero loss. Additionally, the limitations of lithography (a process used to fabricate coupler
100
) create a non-zero gap
206
between the first and second individual waveguides
106
1
,
106
2
. Even if lithography permitted a zero gap, an average value of this gap
206
as the waveguides converge would be finite which is counter to the desired theoretical zero value gap (i.e., the waveguides are overtly non-parallel); thus, creating the insertion loss condition.
SUMMARY OF THE INVENTION
These and other deficiencies of the prior art are addressed by the present invention of an apparatus for optical coupling having a first array of individual waveguides optically communicating with a free space region at a first junction, each waveguide having a tapered region proximate the junction where a gap spacing between tapered regions of adjacent individual waveguides is substantially constant. In one embodiment, the tapered region of each individual waveguide has a length D of approximately 250 &mgr;m. The gap spacing is a minimum amount of space between adjacent individual waveguides and in one embodiment of the invention in the range of approximately 1.5-3.5 &mgr;m. The first array of individual waveguides also has a horn region immediately proximate the tapered region and opposite the first junction with a changing waveguide width. The first array of individual waveguides also has a waveguide region immediately proximate the horn region and opposite the tapered region with a width that is nearly uniform along its entire length. In one embodiment, the width of the tapered region is decreased (tapers) as a function of length as it extends away from the horn region. The apparatus may also have a second array of individual waveguides communicating with the free space region at a second junction.
REFERENCES:
patent: 4904042 (1990-02-01), Dragone
patent: 5136671 (1992-08-01), Dragone
patent: 5745618 (1998-04-01), Li
patent: 5889906 (1999-03-01), Chen
patent: 5987050 (1999-11-01), Doerr et al.
patent: 6058233 (2000-05-01), Dragone
patent: 6141467 (2000-10-01), Doerr
patent: 6240118 (2001-05-01), Doerr et al.
patent: 6385373 (2002-05-01), Doerr et al.
patent: 6396977 (2002-05-01), Dragone
patent: 6434303 (2002-08-01), Temkin et al.
patent: 6493487 (2002-12-01), Temkin et al.
patent: 6553165 (2003-04-01), Temkin et al.
patent: 2003/0138205 (2003-07-01), Dragone
patent: 2003/0194181 (2003-10-01), Dragone
H.S. Kim et al., “Actively gain-flattened erbium-doped fiber amplifier over 35 nm by using all-fiber acoustooptic tunable filters,” IEEE Photon. Technol. Lett., vol. 10, pp. 790-792, Jun. 1998.
M.C. Parker et al., “Dynamic holographic spectral equalization for WDM,” IEEE Photon. Technol. Lett., vol. 9, pp. 529-531, 1997.
J.E. Ford et al., “Dynamic spectral power equalization using micro-opto-mechanics,” IEEE Photon. Technol. Lett., vol. 10, pp. 1440-1442, Oct. 1998.
T. Huang et al., “Performance of a liquid-crystal optical harmonic equalizer,” Optical Fiber Communication Conference, PD29-1-3, 2001.
K. Inoue et al., “Tunable gain equalization using a Mach-Zehnder optical filter in multistage fiber amplifiers,” IEEE Photon. Technol. Lett., vol. 3, pp. 718-720, 1991.
A. Ranalli and B. Fondeur, “Planar tapped delay line based, actively reconfigurable gain-flattening filter,” European Conference on Optical Communication, 2000.
B.J. Offrein, et al., “Adaptive gain equalizer in high-index-contrast SiON Technology,” IEEE Photon. Technol. Lett., vol. 12, pp. 504-506, 2000.
C.R. Doerr et al., “An automatic 40-wavelength channelized equalizer,” IEEE Photon. Technol. Lett., vol. 12, pp. 1195-1197, 2000.
C.R. Doerr et al., “Integrated WDM dynamic power equalizer with potentially low insertion loss,” IEEE Photon. Technol. Lett., vol. 10, pp. 1443-1445, Oct. 1998.
C.R. Doerr et al., “Arrayed waveguide dynamic gain equalization filter with reduced insertion loss and increased dynamic range,” IEEE Photon. Technol. Lett., vol., 13, pp. 329-331, Apr. 2001.
C.R. Doerr et al., “Dynamic Wavelength equalizer in silica using the single-filtered-arm interferometer,” IEEE Photon. Technol. Lett., vol. 11, pp. 581-583, May 1999.
A. Sugita et al., “Very low insertion loss arrayed-waveguide grating with vertically tapered waveguides,” IEEE Photon. Technol. Lett., vol. 12, pp. 1180-1182, Sep. 2000.
Y. Inuoe et al., “Polarization sensitivity of a silica waveguide thermooptic phase shifter for planar lightwave circuits,” IEEE Photon. Technol. Lett., vol. 4, pp. 36-38, Jan. 1992.
K. Koyama et al., “Frequency chirping in external modulators,” J. Lightwave Technol., vol. 6, p. 87, 1988.
LandOfFree
Optical coupler with low loss interconnections 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 coupler with low loss interconnections, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical coupler with low loss interconnections will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3276356