Optical bypass method and architecture
This invention pertains to optical fiber transmission networks, and is particularly relevant to transmission of high volume of data and voice traffic among different locations. In particular, the improvement teaches improvements to an optical transport system to allow for efficient and flexible network evolution.
Latest Celion Networks Inc. Patents:
This application is a continuation of U.S. application Ser. No. 10/454,774, filed Jun. 3, 2003, now pending, which is hereby incorporated by reference in its entirety, which application claims the benefit of Provisional Application No. 60/386,084, filed Jun. 4, 2002, which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTIONThe present invention relates, in general, to the field of optical communications, and in particular to optical fiber transmission networks. The invention is particularly relevant to transmission of high volume of data and voice traffic among different locations. In particular, the invention teaches improvements to an optical transport system to allow for efficient and flexible network evolution. The invention teaches a method and architecture for bypassing a terminal site without affecting existing traffic.
BACKGROUND OF THE INVENTIONA goal of many modern long haul optical transport systems is to provide for the efficient transmission of large volumes of voice traffic and data traffic over trans-continental distances at low costs. Various methods of achieving these goals include time division multiplexing (TDM) and wavelength division multiplexing (WDM). In time division multiplexed systems, data streams comprised of short pulses of light are interleaved in the time domain to achieve high spectral efficiency, and high data rate transport. In wavelength division multiplexed systems, data streams comprised of short pulses of light of different carrier frequencies, or equivalently different wavelengths, are co-propagated in the same fiber to achieve high spectral efficiency, and high data rate transport.
The transmission medium of these systems is typically optical fiber. In addition there is a transmitter and a receiver. The transmitter typically includes a semiconductor diode laser, and supporting electronics. The laser is often a DFB laser stabilized to a specified frequency on the ITU frequency grid. The laser may be directly modulated with a data train with an advantage of low cost, and a disadvantage of low reach and capacity performance. In many long haul systems, the laser is externally modulated using a modulator. A single stage modulator is sufficient for a non-return-zero (NRZ) modulation format. A two stage modulator is typically used with the higher performance return-to-zero (RZ) modulation format. An example of a modulator technology is the Mach-Zehnder lithium niobate modulator. Alternatively, an electro-absorptive modulator may be used. After binary modulation, a high bit may be transmitted as an optical signal level with more power than the optical signal level in a low bit. Often, the optical signal level in a low bit is engineered to be equal to, or approximately equal to zero. In addition to binary modulation, the data can be transmitted with multiple (more than two) levels, although in current optical transport systems, a two-level binary modulation scheme is predominantly employed. The receiver is located at the opposite end of the optical fiber, from the transmitter. The receiver is typically comprised of a semiconductor photodetector and accompanying electronics.
Typical long haul optical transport dense wavelength division multiplexed (DWDM) systems transmit 40 to 80 10 Gbps (gigabit per second) channels across distances of 1000 to 6000 km in a single 30 nm spectral band. In a duplex system, traffic is both transmitted and received between parties at opposite end of the link. In a DWDM system, different channels operating at distinct carrier frequencies are multiplexed using a multiplexer. Such multiplexers may be implemented using array waveguide grating (AWG) technology or thin film technology, or a variety of other technologies. After multiplexing, the optical signals are coupled into the transport fiber for transmission to the receiving end of the link. The total link distance may in today's optical transport systems be two different cities separated by continental distances, from 1000 km to 6000 km, for example. To successfully bridge these distances with sufficient optical signal power relative to noise, the signal is periodically amplified using an in line optical amplifier. Typical span distances between optical amplifiers are 50-100 km. Thus, for example, 30 100 km spans would be used to transmit optical signals between points 3000 km apart. Examples of inline optical amplifiers include erbium doped fiber amplifiers (EDFAs) and semiconductor optical amplifiers (SOAs).
At the receiving end of the link, the optical channels are demultiplexed using a demultiplexer. Such demultiplexers may be implemented using array waveguide (AWG) technology or thin film technology, or a variety of other technologies. Each channel is then optically coupled to separate optical receivers.
Other common variations include the presence of post-amplifiers and pre-amplifiers just before and after the multiplexer and de-multiplexer. Often, there is also included dispersion compensation with the in line amplifiers. These dispersion compensators adjust the phase information of the optical pulses in order to compensate for the chromatic dispersion in the optical fiber while appreciating the role of optical nonlinearities in the optical fiber. Another variation that may be employed is the optical dropping and adding of channels at cities located in between the two end cities. The invention disclosed herein, would find application in any of these variations, as well as others.
Traditionally, optical transport systems are deployed in networks in order to provide connectivity among many cities on a continental or global basis. The selection of type and quantity of equipment is done according to a traffic demand schedule, and differences in demand, or changing demand will consequently change the optimum network design. Modern networks are characterized by large capital and operational costs and must be managed efficiently to be profitable in a competitive market. From a technological standpoint the efficient buildout of a network in a changing traffic demand environment is hampered by the flexibility of current optical transport equipment. There is a need for flexible optical transport systems that support optimal network designs under different traffic loads.
SUMMARY OF THE INVENTIONIn the present invention, improvements to an optical transport system allow for efficient and flexible network evolution. More specifically, the invention teaches a method and architecture for bypassing a terminal site without affecting existing traffic.
In one embodiment of the invention, an architecture for optically bypassing a terminal site is taught.
In another embodiment of the invention, a method for optically bypassing a terminal site is taught.
In another embodiment of the invention, a means of upgrading a terminal site to behave effectively like an optical add-drop (OADM) site is taught.
BRIEF DESCRIPTION OF THE DRAWINGSFor a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments described herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.
In
Also shown in
Also shown in
The invention seeks to eliminate pass through fiber patch cords in a network traffic flexible manner with no impact on the initial cost of the system. Further, since each fiber patch cord pair is connected to a transceiver card, the cost of said card will also be reduced or eliminated due to the benefits of the invention.
In
Also shown in
The signal flow path of the invention may now be understood in reference to
The reverse signal flow is similar, and will now be disclosed explicitly. An input DWDM signal propagating in long haul fiber pair 124 towards terminal 112 is split by optical splitter 208 so that a portion of the signal continues to propagate towards terminal 112 and the remaining portion propagates into optical bypass switch 212. Within optical bypass switch 212, the DWDM signal is decomposed by a diffraction grating or other spectral decomposition device. The separated channels are subsequently attenuated. The attenuation is set so that channel powers will be compatible with those channels that will be combined from the terminal in optical combiner 204. If a particular channel is to be transmitted from terminal 110, optical bypass switch 212 extinguishes that channel's wavelength. In normal mode of operation, if a particular channel is to be received in terminal 112 optical bypass switch 212 extinguishes that channel's wavelength. In broadcast mode of operation, if a particular channel is to be received in terminal 112 optical bypass switch 212 does not extinguish that channel's wavelength; however in this mode, terminal 110 may not transmit at this wavelength. The remaining channels are then recombined in optical bypass switch 212 and output optical bypass switch 212. The output signal is combined with the transmitted signals from terminal 110 in optical combiner 204.
In a preferred embodiment optical bypass switch 210 and optical bypass switch 0.212 are combined in a single bidirectional optical bypass switch commercially sold as a bidirectional dynamic spectral equalizer.
This architecture and method of creating optical bypass of a terminal node allows for the recovery of expensive transceivers at a terminal site, regardless of when the terminal was deployed. The optical bypass architecture may be designed and deployed for a wide variety of existing equipment in current networks. The programmability of optical bypass switch 210 and optical bypass switch 212 eliminates detailed pre-planning of a network which leads to inefficiency.
An important aspect of this invention is that only optical splitter 202, optical combiner 204, optical combiner 206 and optical splitter 208 need be installed with the system at initial deployment. In this manner, optical bypass switch 210 and optical bypass switch 212 can be deployed in a non-traffic effecting manner at the point in time when a sufficient amount of bypass traffic exists.
In
In
Referring now to
Referring now to
Referring now to
In
While this invention has been described in reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
Claims
1. An architecture for optically bypassing a terminal site comprising:
- an optical de-coupler;
- an optical bypass switch optically coupled to an output port of said optical decoupler;
- an optical coupler optically coupled to an output port of said optical bypass switch.
2. The architecture of claim 1 further comprising:
- a second optical decoupler,
- a second optical bypass wavelength switch optically coupled to an output port of said second optical de-coupler,
- a second optical coupler optically coupled to an output port of said second optical bypass switch.
3. The architecture of claim 1 wherein the optical decoupler is a thin film optical decoupler.
4. The architecture of claim 1 wherein the optical decoupler is a fused optical decoupler.
5. The architecture of claim 1 wherein the optical coupler is a thin film coupler.
6. The architecture of claim 1 wherein the optical coupler is a fused optical coupler.
7. The architecture of claim 1 wherein the bypass switch is a dynamic spectral equalizer.
8. A terminal for use in an optical bypass system comprising:
- an optical splitter connected to an incoming optical fiber;
- a first amplifier connected to the optical splitter;
- at least one optical receiver connected to the optical amplifier;
- an optical combiner connected to an outgoing optical fiber;
- a second amplifier connected to the optical combiner;
- at least one optical transmitter connected to the second amplifier.
9. The terminal of claim 8 wherein the first amplifier is a multi stage amplifier.
10. The terminal of claim 9 wherein a dispersion compensation module is interposed in the first amplifier.
11. The terminal of claim 8 wherein the second amplifier is a multi stage amplifier.
12. The terminal of claim 11 wherein a dispersion compensator module is interposed in the second amplifier.
13. The terminal of claim 8 wherein the optical splitter is connected to a first bypass switch.
14. The terminal of claim 13 wherein the first bypass switch is a dynamic spectral equalizer.
15. The terminal of claim 8 wherein the optical combiner is connected to a second bypass switch.
16. The terminal of claim 15 wherein the second bypass switch is a dynamic spectral equalizer.
17. A terminal for use in an optical bypass system comprising:
- a first amplifier connected an incoming optical fiber;
- an optical splitter connected to the first amplifier;
- at least one optical receiver connected to the optical splitter;
- a second amplifier connected to an outgoing optical fiber;
- an optical combiner connected to the second amplifier;
- at least one optical transmitter connected to the optical combiner.
18. The terminal of claim 17 wherein the first amplifier is a multi stage amplifier.
19. The terminal of claim 18 wherein a dispersion compensation module is interposed in the first amplifier.
20. The terminal of claim 17 wherein the second amplifier is a multi stage amplifier.
21. The terminal of claim 20 wherein a dispersion compensator module is interposed in the second amplifier.
22. The terminal of claim 17 wherein the optical splitter is connected to a first bypass switch.
23. The terminal of claim 22 wherein the first bypass switch is a dynamic spectral equalizer.
24. The terminal of claim 17 wherein the optical combiner is connected to a second bypass switch.
25. The terminal of claim 24 wherein the second bypass switch is a dynamic spectral equalizer.
26. A terminal for use in an optical bypass system comprising:
- a first amplifier connected to an incoming optical fiber;
- an optical splitter connected to the first amplifier;
- at least one optical receiver connected to the optical splitter;
- an optical combiner connected to an outgoing optical fiber;
- a second amplifier connected to the optical combiner;
- at least one optical transmitter connected to the second amplifier.
27. The terminal of claim 26 wherein the first amplifier is a multi stage amplifier.
28. The terminal of claim 27 wherein a dispersion compensation module is interposed in the first amplifier.
29. The terminal of claim 26 wherein the second amplifier is a multi stage amplifier.
30. The terminal of claim 29 wherein a dispersion compensator module is interposed in the second amplifier.
31. The terminal of claim 26 wherein the optical splitter is connected to a first bypass switch.
32. The terminal of claim 31 wherein the first bypass switch is a dynamic spectral equalizer.
33. A terminal for use in an optical bypass system comprising:
- an incoming multi stage amplifier having at least an incoming first stage and an incoming second stage connected to an incoming optical fiber;
- a first dispersion compensation module connected to the incoming first stage;
- an optical splitter connected to the first dispersion compensation module and to the incoming second stage;
- at least one optical receiver connected to the incoming second stage;
- an outgoing multi stage amplifier having at least an outgoing first stage and an outgoing second stage connected to an outgoing optical fiber;
- an optical combiner connected to the outgoing second stage;
- a dispersion compensator module connected to the optical combiner;
- the outgoing first stage connected to the dispersion combiner;
- at least one optical transmitter connected to the outgoing first stage.
34. The terminal of claim 33 wherein the optical splitter is connected to a first bypass switch.
35. The terminal of claim 34 wherein the first bypass switch is a dynamic spectral equalizer.
36. A method for optically bypassing a terminal site comprising the steps of:
- installing a terminal at an optical site in an optical network;
- installing an optical splitter and an optical combiner in conjunction with the terminal;
- adding one or more channels to the optical network;
- deploying one or more optical bypass switches if economically justified;
- recovering redundant hardware in the optical network.
37. A method for adding splitters and combiners at a terminal site comprising the steps of:
- installing a terminal at an optical site an optical network;
- adding one or more channels to the optical network;
- determining if the splitter and combiner are economically justified;
- if adding the splitter and combiner are justified then taking traffic out of surface, installing the splitters and combiners, installing an optical bypass switch and recovering hardware in the optical network; and
- if adding the splitter and combiner are not justified, continuing to add one or more channels to the optical network.
Type: Application
Filed: Jun 6, 2005
Publication Date: Oct 13, 2005
Applicant: Celion Networks Inc. (Richardson, TX)
Inventor: Marvin Young (Richardson, TX)
Application Number: 11/146,436