Multiaxial optical coupler

Details Multiaxial optical coupler Multiaxial optical coupler

1998-11-23

2001-05-29

Font, Frank G. (Department: 2877)

Optical waveguides

With disengagable mechanical connector

Optical fiber/optical fiber cable termination structure

C385S066000, C385S067000, C385S068000, C385S073000, C385S074000, C385S084000

Reexamination Certificate

active

06238102

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiaxial optical coupler, and more particularly to a multiaxial optical coupler for achieving optical coupling between end faces of a plurality of optical waveguides and the same number of optical fibers via a lens.
2. Description of the Related Art
The technique of multiaxial optical coupling is essential to an acoustic optical tunable filter (AOTF), a lithium niobate (LiNbO3; LN) modulator, etc. for use in an add drop multiplexer (ADM) which is a data multiplex transmission device arranged at an intermediate portion of a two-way optical transmission path. Multiaxial optical coupling makes it possible to pass optical signals between a plurality of optical waveguides (generally two optical waveguides) and the same number of optical fibers.
Conventionally, there have been proposed e.g. the following multiaxial optical couplers:
FIG. 11
shows a direct fiber coupler applied to an AOTF. A substrate
110
is formed with an optical path of optical waveguides
111
a,
111
b,
111
c
and an optical path of optical waveguides
112
a,
112
b,
112
c.
These optical paths meet each other at two intersection points. A combshaped electrode
113
is arranged across the waveguides
111
b,
112
b,
for applying RF frequency voltage from an RF frequency oscillator
114
thereto.
Further, an auxiliary member
115
is provided on an upper surface of a left end portion of the substrate
110
, for protecting the end faces of the waveguides
111
a,
112
a.
The waveguide
111
a
is coupled to an optical fiber
101
, while the waveguide
112
a
is coupled to an optical fiber
102
.
Similarly, an auxiliary member
116
is provided on an upper surface of a right end portion of the substrate
110
, for protecting the end faces of the waveguides
111
c,
112
c.
The waveguide
111
c
is coupled to an optical fiber
121
, while the waveguide
112
c
is coupled to an optical fiber
122
.
To couple the waveguide
111
c
and the optical fiber
121
to each other, an end of the optical fiber
121
is pressed against the end face of the waveguide
111
c
directly, and after final adjustment, the waveguide
111
c
and the optical fiber
121
are bonded to each other. The waveguides
111
a,
112
a,
and
112
c
are coupled to the optical fibers
101
,
102
, and
122
, in the same manner.
In the AOTF as described above, two optical beams having respective wavelengths &lgr;1 and &lgr;2 are inputted e.g. from the optical fiber
101
. When RF frequency voltage having a frequency f
1
is generated by the RF frequency oscillator
114
and applied to the combshaped electrode
113
, a surface acoustic wave (SAW) is generated over the surface of the substrate
110
to change the direction of polarization of only the laser beam having the wavelength &lgr;1. As a result, the beam having the wavelength &lgr;1 is outputted from the optical fiber
122
, and the beam having the wavelength &lgr;2 from the optical fiber
121
. Thus, it is possible to take out the beam having the wavelength &lgr;1 alone. Similarly, it is possible to take out the beam of the wavelength &lgr;2 from the optical fiber
122
by applying RF frequency voltage having a frequency f
2
, which is generated by the RF frequency oscillator
114
, to the combshaped electrode
113
. The dropping capability of the ADM can be realized by this action.
On the other hand, if an optical beam having a wavelength &lgr;2 is inputted to the optical fiber
101
and an optical beam having a wavelength &lgr;1 to the optical fiber
102
, and then RF frequency voltage having a frequency f
1
, which is generated by the RF frequency oscillator
114
, is applied to the combshaped electrode
113
, it is possible to obtain the beams of wavelengths &lgr;1 and &lgr;2 from the optical fiber
121
. The adding capability of the ADM can be realized by this action.
FIG. 12
shows a conventional V-groove coupler. In this coupler, in the surface of an Si substrate
130
formed with optical waveguides
131
,
132
, V grooves
133
,
134
are formed in a manner extending from ends of the optical waveguides
131
,
132
, respectively, in the same axial directions. Optical fibers
141
,
142
are fitted in the V grooves
133
,
134
, respectively, whereby direct optical coupling is achieved between the optical fibers
141
,
142
and the optical waveguides
131
,
132
, respectively.
FIG. 13
shows a conventional array lens coupler. In this coupler, an array of microlenses
170
is interposed between a substrate
150
formed with optical waveguides
151
,
152
and ferrules
161
,
162
containing respective optical fibers
161
a,
162
a,
whereby optical couplings are effected between the optical waveguides
151
,
152
and the optical fibers
161
a,
162
a,
respectively, via the microlens array
170
. After adjusting the positions of the coupled members for optimization, a metal holder for retaining the microlens array
170
is laser welded so as to prevent displacement of the members from the adjusted positions.
FIG. 14
shows a conventional 2-core ferrule coupler. In this coupler, an aspherical lens
200
is interposed between a substrate
180
formed with optical waveguides
181
,
182
and a 2-core ferrule
190
containing optical fibers
191
,
192
, and optical coupling is effected between the optical waveguides
181
,
182
and the optical fibers
191
,
192
, respectively, via the aspherical lens
200
. Similarly to the above array lens coupler, after adjusting the positions of the coupled members for optimization, a metal holder for retaining the aspherical lens
200
is laser welded so as to prevent displacement of the members from the adjusted positions. This coupler may employ a spherical lens instead of the aspherical lens
200
.
Generally, in an AOTF or the like, LiNbO3 is used as a material for a substrate on which optical waveguides are formed, and hence there is a need for a multiaxial optical coupling method applicable to substrates of this kind of material. Further, it is desired that this kind of device can deliver a predetermined performance over a wide temperature range.
In the direct fiber coupler shown in
FIG. 11
, the end faces of the waveguides
111
,
112
are bonded to the respective optical fibers
121
,
122
, by an adhesive. However, the glass transition temperature is in the range of approximately 50 to 60° C. Therefore, if the temperature of the junctions of the waveguides
111
,
112
and the optical fibers
121
,
122
due to changes in fixing intensity of the adhesive or the like exceed a glass transition point, the end faces of the waveguides
111
,
112
can be displaced from the bonded end faces of the optical fibers
121
,
122
. Now, a device necessitating means for optical coupling which will come into use is expected to have an operating temperatur e range of e.g. 0 to 85° C., so that the conventional direct fiber coupler is likely to cause large insertion loss. For this reason, it is impossible to use the above type of direct fiber coupler.
Further, the direct fiber coupler is unreliable in that an increase in load due to temperature cycling or the like can cause degradation of the bonded portions.
Still further, direct optical coupling produces portions different in refractive index, and hence it is impossible to set return loss to a large value (above 30 dB) after modularization.
In the V-groove coupler shown in
FIG. 12
, the V grooves
133
,
134
are formed on the Si substrate
130
. The Si substrate
130
allows the grooves
133
,
134
to be formed accurately at a low cost. However, it is impossible to form the V grooves on a LiNbO3 substrate accurately at a low cost.
Accordingly, to apply the coupling method using the V grooves to a coupler using a LiNbO3 substrate, it is required, as shown in
FIG. 15
, to form V grooves on a Si substrate
220
, fit optical fibers
221
,
222
in the respective grooves, and then join the Si substrate
220
to a LiNbO3 substrate
210
formed with optical waveguides
211
,
212
. However, it is extremely difficult

Affiliated with

Also associated with

Rating

Multiaxial optical coupler does not yet have a rating. At this time, there are no reviews or comments for this patent.

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

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2567852