Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2001-03-22
2003-06-24
Kim, Robert H. (Department: 2882)
Optical waveguides
With optical coupler
Plural
C385S016000, C359S199200, C359S199200
Reexamination Certificate
active
06584245
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to fiber optic communications and, more particularly, to high speed data links for use with light modulation systems including a superconductive plate assembly in a data transmission scheme.
The light modulation system as disclosed in U.S. Pat. No. 5,768,002 is capable of transmitting optical data signals at high data rates such as, for example, rates of terabits per second (Tbit/s) at a given wavelength over a single optical fiber. For example, the light modulation system can be used in a wavelength-division multiplexing (WDM) system to provide the optical data signal at a WDM channel.
However, in order to achieve a complete data link capable of handling optical data signals at a single wavelength at Tbit/s rates, an optical receiver in the data link must be able to detect the optical data signals at Tbit/s rates. Such an optical receiver singly capable of detecting Tbit/s optical data signals of a single wavelength is not commercially available at the present time to the applicant's knowledge. Although optical detectors capable of detecting optical signals at a rate of 750 GHz or with response times on the order of picoseconds or less are known in the art, these devices are still in their experimental stages hence are not yet commercialized.
Prior art data links have not had to deal with this problem of the unavailability of Tbit/s rate optical receivers because light modulation systems capable of transmitting optical data signals at Tbit/s rates at a given wavelength are not currently known at this time to the applicant's knowledge, with the exception of the light modulation system disclosed in U.S. Pat. No. 5,768,002. Existing high speed light modulation systems generally consist of a series of N light modulators, each light modulator corresponding to one channel out of N channels and producing optical data signals at rates of less than Tbit/s at a unique wavelength corresponding to a particular WDM channel out of a range of wavelengths &lgr;
1
−&lgr;
N
. The multitude of optical data signals over the range of wavelengths, each optical data signal having its own unique wavelength, are multiplexed onto an optical fiber. The multiplexed signal is received by a demultiplexer which separates the multiplexed signal into the separate optical data signals according to wavelength. The separated optical data signals are then detected by a plurality of optical detectors, each operating at less than Tbit/s rates.
The prior art data link as a whole can be made to transmit data at Tbit/s rates by using a plurality of data sources, optical sources and optical detectors all operating at Gbit/s rates. For example, if a hundred optical sources are provided (i.e., N=100), with each optical source generating an optical signal at 10 Gbit/s and at a distinct wavelength out of the wavelength range &lgr;
1
through &lgr;
100
, then the aggregate optical data rate is one Tbit/s. Following transmission through an optical fiber, a WDM multiplexer combines the one hundred optical signals such that the resulting multiplexed signal contains all optical signals of the wavelength range &lgr;
1
through &lgr;
100
. The WDM demultiplexer then separates the multiplexed signal into distinct wavelengths to be detected by a hundred optical detectors, each detector operating at 10 Gbits/s. As a result, it is possible to transmit data using the prior art data link at an aggregate rate of 1 Tbit/s.
It is submitted, however, the aforedescribed prior art data link has a number of disadvantages. In order to increase the total data transmission rate of the prior art data link above approximately 1 Tbit/s, the number of channels, and hence the number of data sources and optical sources used in the data link, must be increased. This condition may be satisfied by narrowing the wavelength differences between channels thus fitting more channels into a given wavelength range &lgr;
1
through &lgr;
N
and/or widening the wavelength range between &lgr;
1
and &lgr;
N
. However, narrowing the wavelength differences between the channels increases the probability of data transmission error due to potential optical signal overlap and crosstalk and puts a greater demand on the WDM demultiplexer to accurately separate the optical signals into the distinct wavelengths. As is well known in the art, there is only a finite range available for use as the wavelength range &lgr;
1
through &lgr;
N
, outside of which significant optical signal loss occurs due to the material properties of the optical fiber as well as other components of an optical communication system, such as repeaters and amplifiers. Therefore, the wavelength range cannot be widened indefinitely using currently available technology, hence it is difficult to increase the number of channels to increase the data transmission rate. Furthermore, increasing the number of different wavelengths traveling simultaneously through the optical fiber also increases the probability of occurrence of undesired, nonlinear optical effects during transmission. Care must be taken to avoid such nonlinear optical effects, thus adding to the overall complexity and cost of this prior art data link at faster data transmission rates. Still further, WDM channels require a guard band on either side of the specific channel wavelength in order to reduce wavelength overlap and crosstalk between channels. Since no data can be transmitted on the guard band, the wavelengths used in the guard band are essentially wasted bandwidth.
The present invention provides a high speed data link which serves to resolve the problems described above with regard to prior art data links in a heretofore unseen and highly advantageous way and which provides still further advantages.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, there is disclosed herein a high speed data link including a transmitting arrangement having a transmitter output. The transmitting arrangement includes a source of light having a certain wavelength. The transmitting arrangement further includes a layer of superconductive material through which the light from the source must pass before the light can reach the transmitter output. The superconductive material is switchable between a superconducting state in which,the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Still further, the transmitting arrangement includes an arrangement for switching the superconductive material between its superconducting and non-superconducting states to provide a train of light pulses having the certain wavelength and containing optical data. The transmitting arrangement further includes a wavelength changing device, which is optically coupled to the layer of superconductive material, for changing the wavelength of the light pulses and providing a train of wavelength changed light pulses containing optical data at the transmitter output. The high speed data link also includes an optical fiber, one end of which is optically coupled to the transmitter output, for directing the train-of wavelength changed light pulses away from the transmitting arrangement. Additionally, the high speed data link includes a receiving arrangement optically coupled to an opposing end of the optical fiber. The receiving arrangement includes an all-optical demultiplexer for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses. The receiving arrangement further includes a series of optical receivers, each optical receiver being designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.
In another aspect of the invention, the transmitting arrangement of the high speed data link includes a series of light modulating devices for generating a series of trains of light pulses over a specified range of wavelengths. Each light modulating device has a light output and provi
Kim Robert H.
Morita Yoriko
Suchecki Krystyna
TeraComm Research, Inc
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