Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2002-04-30
2004-12-07
Patel, Nimeshkumar D. (Department: 2879)
Optical waveguides
With optical coupler
Switch
C385S017000, C359S199200
Reexamination Certificate
active
06829401
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical communication equipment.
2. Description of the Related Art
FIG. 1
shows a representative switch
100
of the prior art for routing data in a modem communication system. Switch
100
is a 3×3 switch that can route data from any one of its three inputs to any one of its three outputs. Switch
100
comprises a 3×3 arrayed waveguide grating (AWG)
104
, three transmitter cards
106
coupled to input ports of AWG
104
, and three receivers
130
coupled to output ports of AWG
104
. Each transmitter card
106
is configured to receive a corresponding electrical stream of data, convert it into an optical signal, and send that optical signal to AWG
104
. AWG
104
is a solid state device configured to redirect light entering any one of the input ports to a selected output port based on its wavelength. Each receiver
130
is configured to receive an optical signal from one of the output ports of AWG
104
and convert it back into a corresponding electrical data stream.
Each transmitter card
106
comprises a tunable laser
110
and a modulator
120
. Laser
110
feeds an optical carrier signal into modulator
120
. Modulator
120
modulates the carrier signal with data based on the corresponding electrical input data stream to produce an optical data-modulated output signal of the respective transmitter card
106
. Each transmitter card
106
can be configured to send data to any chosen receiver
130
by setting the wavelength of laser
110
to the value for the corresponding output port of AWG
104
. Depending on the implementation of AWG
104
, lasers
110
corresponding to different input ports of AWG
104
may be tunable over different wavelength ranges.
The capacity of a switch, such as switch
100
, defined as the number of ports multiplied by the throughput of each port is measured, e.g., in Gigabits per second (Gb/s). To meet the demands of ever-increasing data traffic in communication networks, switches of relatively large capacity are desirable. However, direct scaling of the switch architecture illustrated in
FIG. 1
may not increase the switch capacity in proportion to the increasing switch size because the switch capacity is a convoluted function of many different parameters. For example, any one or a combination of the following may limit the capacity of switch
100
: (i) the tuning range of lasers
110
; (ii) the physical dimensions of the wafer on which AWG
104
is implemented and therefore the number of AWG channels; and/or (iii) the tolerable level of inter-channel crosstalk.
SUMMARY OF THE INVENTION
According to certain embodiments, the present invention provides a parallelized switch of increased capacity. The switch employs two or more parallel optical switch fabrics, e.g., arrayed waveguide gratings (AWG), combined with a set of transmitter cards. Each transmitter card has a tunable laser and two or more modulators, each configured to modulate a different copy of the output of the laser with a different set of data. Outputs of the modulators in each transmitter card are coupled to a set of corresponding input ports in the AWGs. A set of receiver cards, each receiver card having a number of receivers matching that of modulators in the transmitter cards, is coupled to output ports of the AWGs, such that each receiver card receives signals from a set of corresponding output ports in the AWGs. Each transmitter card can be configured to send data to any receiver card by setting the wavelength of its laser to the value corresponding to the set of output ports in the AWGs coupled to that receiver card. A parallelized switch of the present invention may be optimized based on a desired set of criteria, e.g., capacity, cost, and/or size.
According to one embodiment, the present invention is an apparatus, comprising: (A) J optical switch fabrics (OSF), each OSF having N input ports and N output ports and configured to route optical signals from the input ports to the output ports based on wavelength, where J and N are integers greater than one; (B) N transmitter cards, each transmitter card comprising a tunable laser and J modulators, each modulator configured to modulate a signal generated by said tunable laser with data, wherein the J modulators are coupled to J corresponding input ports of the J OSFs; and (C) N receiver cards, each receiver card comprising J receivers coupled to J corresponding output ports of the J OSFs, wherein the apparatus is configured to route data from any transmitter card to any receiver card.
According to another embodiment, the present invention is a method of transmitting data, comprising the steps of: (i) modulating an optical signal generated by a tunable laser with data using J modulators to produce J data-modulated optical signals, where J is an integer greater than one; and (ii) routing the J data-modulated optical signals using J optical switch fabrics (OSF), wherein: each OSF has N input ports and N output ports and is configured to route optical signals from the input ports to the output ports based on wavelength, where N is an integer greater than one; and the J modulators are coupled to J corresponding input ports of the J OSFs.
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Duelk Marcus
Gripp Jurgen
Dong Dalei
Lucent Technologies - Inc.
Patel Nimeshkumar D.
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