Optical integrated module

Details Optical integrated module Optical integrated module

2000-12-28

2003-04-29

Bovernick, Rodney (Department: 2874)

Optical waveguides

Integrated optical circuit

C385S031000, C385S032000, C385S050000

Reexamination Certificate

active

06556735

ABSTRACT:

The present invention relates to an optical integrated module created with hybrid photonic integration technology, and in particular relates to an optical integrated nodule configured by disposing an optical waveguide device between an input optical waveguide and an output optical waveguide.
BACKGROUND ART
As communication demand shifts from low speed service lead by telephones to broadband digital multimedia service, development of an optical ATM switching equipment having a high speed and high throughput for efficiently multiplexing whole these communication services and an optical switch having a high speed and excellent expandability as mainstay thereof is desired. Among all, a distribution selective optical switch configured by combining a one-input one-output high speed optical gate device and an optical multiplexer-demultiplexer device together is controlled easily, and therefore application for such use is being studied. In order to realize such an optical switch network, excellent crosstalk suppressing performance for satisfying scalability, high speed switching performance, and simple control system appropriate for speeding-up is required. Therefore, as this high speed optical gate, an optical gate device (SOAG) using semiconductor optical-amplifier (SOA) which has extremely high ON/OFF performance around 40 dB to 70 dB and can compensate loss of the optical multiplexer-demultiplexer device, and can be expected to respond at high speed of the order of nanosecond (nsec) is catching attention. In addition, in such a system that a number of such optical devices are used, costs as well as implementation load that these occupy the whole system cannot be ignored. Therefore, expectation toward a photonic integrated circuit (Photonic IC: PIC) which brings a plurality of optical devices into monosilic integration on one substrate and realizes a particular function and a photonic/electric integrated module that brings periphery electronic circuit devices, etc. for driving optical devices into integral integration is heightening. In particular, a hybrid optical integrated module in which a semiconductor optical device is implemented on an optical waveguide platform is expected as photonic integration technology that is closest to practical use from a point of view of its productivity, etc.
FIG. 10
is a plan block diagram showing an example thereof, in which an optical waveguide device
101
such as SOAG, having an optical waveguide
102
linked with the above described respective optical waveguides
104
and
105
are mounted on an optical waveguide platform
103
on which an input optical waveguide
104
and an output optical waveguide
105
. In this hybrid photonic integrated device, the input optical signal
107
emitted into the input optical waveguide
104
is wave-guided through the input optical waveguide
104
and inputted to the optical waveguide device
101
, and after being wave-guided through the optical waveguide
102
, is wave-guided through the output optical waveguide
105
and is outputted as a core optical signal
108
.
In the case where the optical integrated module on which the above described SOAG is mounted by application of hybrid photonic integration technology, in order to compensate a coupling loss due to relatively large optical waveguide discontinuity as between the input optical waveguide
104
and the optical waveguide
102
of the optical waveguide device
101
or between the optical waveguide
102
and the output optical waveguide
105
, or a branching loss of the optical multiplexer-demultiplexer device, SOAG itself is required to have a large optical signal gain. Thus, measures to control residual facet reflection as much as possible is required to be taken, and therefore, angled facet structure in which the optical waveguide is bent in the vicinity of the light incident and emission facet obliquely toward this facet, or alternatively a window structure that discontinues the active stripe (active layer) immediately in front of the facet, etc. are proposed. For example, in
FIG. 11
, taken is such a configuration that toward the incident direction of the input optical signal
117
as well as the emitting direction of the output optical signal
118
, the input optical waveguides
114
as well as the output optical waveguides
115
are inclined at a required angle and following this, portions connected with at least the input optical waveguides
114
and the output optical waveguides
115
in the optical waveguides
112
provided in the optical waveguide device
111
.
However, in the hybrid optical integrated module shown in these FIG.
10
and
FIG. 11
, the optical signals to be emitted into the optical waveguide devices
101
and
111
subject to wave-guiding through the input optical waveguides
104
and
114
become unguided optical signal component which do not attribute to optical coupling in majority thereof in comparatively major discontinuity of optical waveguide between the input optical waveguide and the optical wave-guide device. This unguided optical signal component is brought into coupling again in the region of discontinuity of the optical waveguide in the optical waveguide devices
101
and
111
and the output optical waveguides
105
and
115
, and this remarkably deteriorates overall ON/OFF performance toward optical signal of the optical gate device module. That is, majority of the unguided optical signals at the light incident side of the optical waveguide devices
101
and
111
are caused to go straight forward subject to gradual diversion like a beam in the substrate of the optical waveguide device
101
and
111
to reach the facet of the optical waveguide at the emitting side in the opposite side. Thus, the unguided optical signal(s) is (are) coupled into the output optical waveguides
105
and
115
existing in the vicinity thereof at a certain rate. This phenomenon becomes a cause to deteriorate the optical characteristics of the optical integrated module, in particular the ON/OFF characteristics of the optical signal in the optical gate device module such as, SOAG. Such an ON/OFF introduces coherent cross talk (beat noise) in optical signals and remarkably spoil the characteristics of the optical modules.
Particularly in case of an optical waveguide array device, such problems may be structurally caused by the fact that the emitting position of the unguided optical signals to be extremely closer to the emitting optical waveguide of another channel. For example, as shown in
FIG. 12
, in the case where the angled facet (angled facet) of the output optical waveguide
125
is formed in parallel along the angled facet of the input optical waveguide
124
, since actually almost all of them is formed in point symmetry due to convenience in manufacturing, as a consequence, the propagation axis of the unguided optical signal (unguided signal) between the input optical waveguide
124
and the optical waveguide device
121
corresponds with an angle which is most apt to get coupled with the output optical waveguide
125
. This introduces remarkable deterioration in inter-channel crosstalk suppressing characteristics.
In order to control such leakage of unguided optical signals, such measures that improve coupling loss so as to control occurrence of unguided optical signals themselves are first necessary. However, it is essentially impossibly to make coupling loss into zero in a hybrid optical integrated module, and a new device indeed for not coupling the unguided optical signal component as mulch as possible will rather become more important. However, it is the current state that none that can tolerate for practical use as a method to remove such unguided optical signal component effectively has been realized yet.
An object of the present invention is to provide an optical integrated module that has enabled to get rid of influence that the unguided optical signal given rise to due to discontinuity of optical waveguide essentially inevitable in hybrid photonic integration affects optical switching performance.
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