Optical waveguides – Integrated optical circuit
Reexamination Certificate
2000-09-08
2002-05-07
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Integrated optical circuit
C385S024000, C385S037000, C385S016000, C359S199200, C359S199200
Reexamination Certificate
active
06385362
ABSTRACT:
TECHNICAL FIELD
This invention relates to photonic modules that have the ability to add and drop specific information-carrying wavelengths propagating within a fiber optic network, hereinafter referred to as optical add/drop multiplexers (OADM).
BACKGROUND
Optical add/drop multiplexers (OADM) have the ability to add and drop specific information-carrying wavelengths propagating within a fiber optic network. A block diagram illustrating how an OADM
1
functions to add wavelengths &lgr;′
i
. . . &lgr;′
j
. . . &lgr;′
k
and drop wavelengths &lgr;′
i
. . . &lgr;′
j
. . . &lgr;′
k
from an input &lgr;
1
-&lgr;
N
is shown in FIG.
1
.
A widely discussed architecture for OADMs involves using arrayed waveguide grating (AWG) routers and 2×2 optical switches. This architecture is schematically shown in FIG.
2
. Here, AWGs
12
are used as multiplexers/demultiplexers and switches
14
are used for selecting the channels to be added and dropped. This architecture can be made with commercially available, stand-alone components (e.g., a fiber pigtailed AWG that is then connected to fiber pigtailed switches by fusion splicing and connector attachment). AWGs are produced commercially by, for example, Hitachi, Lucent, Nortel, SDL, and JDS Uniphase. 2×2 switches, in both opto-mechanical and thermo-optical varieties, are produced commercially by vendors such as JDS Uniphase, Fitel, Dicon, and Corning.
Unfortunately, the architecture illustrated in
FIG. 2
has a number of shortcomings. This architecture is difficult to assemble due to the number of fiber connections, and is expensive. In addition, this architecture suffers from a high insertion loss. Furthermore, this architecture scales very poorly as the number of wavelengths is increased. Metropolitan area network applications, for example, may demand that 32, 64 or 80 wavelengths be added or dropped in a given OADM.
To solve these problems, attempts have been made in the prior art to integrate the filtering function of AWGs and the switching function of switches on a single substrate. One such attempt, using a planar glass technology, is described by K. Okamoto et al. in their paper entitled, “16-Channel Optical Add/Drop Multiplexer Consisting of Arrayed Waveguide Gratings and Double Gate Switches,”
Electronic Letters
32, 1471 (1996). Here, several AWGs were made in planar glass (silica on silicon) on the same substrate, and Mach-Zehnder-based thermo-optic switches were integrated on the same substrate. Unfortunately, there are several disadvantages to this approach. Mach-Zehnder-based switches require a large amount of area on the chip. In addition, Mach-Zehnder-based switches are very sensitive to fabrication errors and suffer from poor isolation.
Another attempt toward an integrated OADM has been described by Giles et al. in their paper entitled, “Reconfigurable 16-Channel WDM Drop Module Using Silicon MEMS Optical Switches,”
IEEE Photonics Tech. Lett
. 11, 63 (1999). Here, AWGs are fiber-coupled to an array of MEMS-type switches. Unfortunately, this approach is not fully integrated and is not solid-state.
Clearly, there is a need for a solid-state OADM that is fully integrated on a single substrate and not sensitive to fabrication errors. Ideally, the switches used in such an OADM should not require large areas on the chip and should further have good isolation characteristics.
SUMMARY OF THE INVENTION
The present invention provides an integrated, high performance optical add/drop multiplexer (OADM) comprising a multilayer stack whose function is to add or drop specific information-carrying wavelengths propagating within a fiber optic communication network. The stack structure eliminates or at least ameliorates the shortcomings associated with the prior art. The stack comprises a first layer comprising a silicon or silica substrate, a second layer comprising an undercladding layer, a third layer comprising a core glass layer, and a fourth layer comprising an overcladding layer. In another embodiment, the stack comprises a first layer comprising a silicon or silica substrate, a second layer comprising an undercladding layer, a third layer comprising a polymer layer, a fourth layer comprising a core glass layer, and a fifth layer comprising an overcladding layer.
The invention also provides an integrated optical add/drop multiplexer (OADM) comprising a substrate, an undercladding layer disposed on the substrate, a core glass layer disposed on a portion of the undercladding layer, and an overcladding layer disposed on the undercladding layer and the core glass layer. The core glass layer includes an arrayed waveguide grating (AWG) and the overcladding layer comprises a polymer and includes an optical switch.
The invention also provides an integrated optical add/drop multiplexer (OADM) comprising a substrate, an undercladding layer disposed on the substrate, a core glass layer disposed on a portion of the undercladding layer, a polymer layer disposed on the undercladding layer adjacent the core glass layer, and an overcladding layer disposed on the polymer layer and the core glass layer. The core glass layer includes an arrayed waveguide grating (AWG) and the polymer layer includes an optical switch.
REFERENCES:
patent: 5546483 (1996-08-01), Inoue et al.
patent: 5857039 (1999-01-01), Bosc et al.
patent: 5859941 (1999-01-01), Horita et al.
patent: 6084050 (2000-07-01), Ooba et al.
patent: 6091870 (2000-07-01), Eldada
patent: 6122416 (2000-09-01), Ooba et al.
Cole Thomas W.
Corning Incorporated
Nixon & Peabody LLP
Palmer Phan T. H.
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