Optical coupling with a test port

An optical coupler comprises a first, second, third, and fourth port. The first port is for communicating optical signals with a processor. The second port receives a first optical signal and transmits the first optical signal to the first port. The third port receives a second optical signal and transmits the second optical signal to the first port. The fourth port receives a third optical signal and transmits the third optical signal to the first port.

FIELD OF THE INVENTION

The invention generally relates to the field of optical communications. More particularly, the invention relates to optical coupling with a test port.

BACKGROUND OF THE INVENTION

The Internet has become increasingly popular in recent years and many homes (and offices, etc.) now have network connections to the Internet. Many portions of the Internet are already implemented with fiber optics and as such, these portions provide high speed communications. For example, fiber optics may exist between Internet Service Providers and distribution points, such as, for example, telephone central offices, cable head ends, and the like.

While some portions of the network connection are fiber optic based, other portions have not yet been implemented with fiber optics or have only been partially implemented with fiber optics. For example, the network connection from a distribution point to a home is typically implemented via a telephone line or a cable line, rather than a fiber optic cable. Because the communication speed of a telephone line or a cable line typically is slower than that of fiber optics, this portion of the network may become the bottleneck for data communication. To overcome this bottleneck, a fiber optic cable may be installed between the distribution point and the home, known as fiber-to-the-home (FTTH).

A typical installation of fiber-to-the-home may include several optical devices, such as, for example, fiber optic cables, optical connectors, optical splices, and the like. For such an installation to function well, the devices should be properly installed. For example, a fiber optic cable should not be excessively bent and optical connectors should be tight and properly aligned. To test for proper installation, an optical testing device may be applied to the distribution point end of a fiber optic cable. If the optical testing device determines that there is a problem, the installer may attempt to diagnose the problem from information provided by the testing device. Otherwise, the fiber optic cable may be connected to the distribution point.

After the fiber optic cables are installed and connected, the testing device may be used to diagnose problems that occur subsequently. This typically requires disconnecting the fiber optic cable at some point to attach the testing device. Such disconnection of the fiber optic cable, however, disrupts signal communication between the distribution point and the home. Such a disruption of communication may be inconvenient to users.

In view of the foregoing, there is a need for a device that provides the ability to test a portion of a fiber optic communication path without having to disrupt data communication.

SUMMARY OF THE INVENTION

An optical coupler comprises a first, second, third, and fourth port. The first port is for communicating optical signals with a processor. The second port receives a first optical signal and transmits the first optical signal to the first port. The third port receives a second optical signal and transmits the second optical signal to the first port. The fourth port receives a third optical signal and transmits the third optical signal to the first port.

The above-listed features, as well as other features, of the invention will be more fully set forth hereinafter.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The optical coupler has a port for connection of an optical testing device. With such an optical coupler, the optical testing device may be connected to an optical network connection or any optical communication medium, and the network connection may be tested without disruption of signal communication.

FIG. 1shows a passive optical network that can provide optical signals from a distribution point to an end user at a home. A passive optical network is a high bandwidth point to multipoint optical fiber network that may based on asynchronous transfer mode protocol, Ethernet, TDM, or the like. Depending on where the passive optical network terminates, the network can be described as fiber-to-the-curb, fiber-to-the-building, or fiber-to-the-home (FTTH). The term “passive” describes a network connection in which there are no power requirements or active electronic parts between the distribution point and the home. As shown inFIG. 1, central office110may function as the distribution point for distributing optical signals. While the distribution point is illustrated as central office110, the distribution point may be a cable head end or any other distribution point for optical signals.

Central office110may include a data optical line termination120, a video optical line termination130, and an optical coupler140. Data optical line termination120is shown as being optically connected to optical coupler140via a fiber optic cable155. Video optical line termination130is shown as being optically connected to optical coupler140via another fiber optic cable155.

Data optical line termination120comprises a first port121and a second port122. First port121may communicate data signals with a network, such as, for example, the Internet, a local area network, a wide area network, another communication device, and the like. Second port122may communicate data signals with home190. In this manner, home190can communicate with a network, such as the Internet. Data signals may include data such as, for example, e-mails, web pages, audio files, video files, and the like.

First port121typically communicates signals optically; however, first port121may communicate signals in other forms, such as, for example, electrical signals, wireless signals, and the like. Second port122optically communicates data signals with home190via optical coupler140. Data optical line termination120, therefore, may convert between electrical signals and optical signals, between wireless signals and optical signals, or may function as a repeater of optical signals.

Video optical line termination130comprises a first port131and a second port132. First port131may communicate video signals with a video source (e.g., a video headend) as shown or with any other communication device. Second port132communicates the video signals with home190via optical coupler140. Typically, video signals are received from the video source and sent to home190, for example, for transmission of a movie, a television show, and the like. First port131typically communicates signals optically; however, first port131may communicate in other forms, such as, for example, electrical signals, wireless signals, and the like. Video optical line termination130, therefore, may convert between electrical signals and optical signals, wireless signals and optical signals, or may function as a repeater of optical signals.

Optical coupler140receives data signals from data optical line termination120and receives video signals from video optical line termination130. Optical coupler140combines the data signals and the video signals for communication over a single optic fiber. One technique for combining the signals is wave division multiplexing. Wave division multiplexing combines data from different sources together on an optical fiber, with each signal being carried at the same time on its own separate light wavelength. One advantage with such a technique is that each signal may be de-multiplexed and processed separately and as such, different signal formats and different signal rates can be transmitted simultaneously on the same optic fiber. For example, an Internet Protocol (IP) signal, a Synchronous Optical Network signal, and an asynchronous transfer mode signal can all be traveling at the same time within the optic fiber.

The combined signals may be sent to home190via a fiber optic cable155. Home190may include an optical network unit192and a computer194. Computer194may alternatively be any data or video appliance, such as, for example, a television, a set top box, a telephone, and the like. While an optical line termination120or130may typically communicate with up to thirty-two optical network units192, for clarity, only one optical network unit192is shown. Optical network unit192receives optical signals from optical coupler140and de-multiplexes the signals. For example, optical network unit192may receive the multiplexed data signal and video signal and de-multiplex the data and video signal for presentation to computer194as two separate signals.

Further, optical network unit192may receive data signals from computer194and may send the received data signal to optical coupler140via fiber optic cable155. For example, optical coupler140may receive data signals from computer194and route those data signals to data optical line termination120, for example. Such routing may be implemented with multi-mode interference coupling that may include a Bragg grating structure comprised of planar SiON/SiO2 waveguides, InGaAsP/InP waveguides, and the like. Further, optical coupler140may be manufactured using fused biconic technology, diffraction grading, planar devices, or the like.

As can be seen, optical coupler140allows at least two different signals to be sent to computer194over a single optic fiber. In addition to providing such multiplexing of video and data signals, optical coupler140provides the ability to test the integrity of the fiber optic network connection between optical coupler140and optical network unit192. Such testing may be initiated to identify problems in the transmission path, such as, for example, a broken fiber optic cable155, an excessively bent fiber optic cable155, and the like. Fiber optic cable155may further include optical splices, optical connectors, and the like that may over time, cause signal communication problems that could also bring about such testing. For example, an optical splice may vibrate loose and cause increased signal communication errors.

With a conventional fiber optic network connection, to test the network, one of the fiber optic cables155typically is disconnected and then connected to an optical testing device. For example, with a conventional coupler, the video connection may be disconnected to make a place to connect the optical testing device. The optical testing device is then used to determine the cause of the signal communication errors. Such disconnection, however, disrupts signal communication with home190. Advantageously, optical coupler140includes the ability to connect an optical testing device and perform optical testing while communication continues uninterrupted between the Internet and computer194.

To test the network connection, an optical time domain reflectometer150may be connected to a test port of optical coupler140. Alternatively, any other optical testing device may be connected to the test port of optical coupler140.

Optical time domain reflectometer150is an optoelectronic instrument that may be used to characterize an optical component, such as, for example, an optical fiber, an optical communication path, an optical communication network, and the like. Optical time domain reflectometer150injects a series of optical pulses into the optical component being tested. It also receives, from the same end of the optics under test, light that is scattered and reflected back from the optical component. The intensity of the return pulses is measured and integrated as a function of time, and is plotted as a function of fiber length. Optical time domain reflectometer150may be used for estimating fiber optic length and overall attenuation, including splice and mated-connector losses. It may also be used to locate faults, such as breaks, excessive bends, and the like.

Optical coupler140combines data signals, video signals, and test signals for communication over a single optic fiber, for example, using wave division multiplexing. Because the test signal is carried on its own separate light wavelength, it does not interfere with the communication of the data and video signals. Moreover, because optical coupler140may combine the test signals, data signals, and video signals, the fiber optic connection does not have to be disconnected, thereby allowing data and video communication to continue.

Further details of optical coupler140are shown inFIG. 2. As shown inFIG. 2, optical coupler140comprises a first port141, a second port142, a third port143, and a fourth port144. First port141is for communicating optical signals with computer194.

Optical coupler140may be adapted to conform to ITU-T Recommendation G.983.3, hereinafter “G.983.3.” G.983.3 defines an allocation of wavelengths for the multiplexed optical signals in a FTTH system. G.983.3 allocates wavelengths of 1480 to 1500 nanometers for transmission of data signals to the home and wavelengths of 1260 to 1360 nanometers for transmission of data signals from the home. G.983.3 also allocates wavelengths for an “enhancement band.” The enhancement band allocation typically is used for video signals and has two options. The first option allocates wavelengths of 1539 to 1565 nanometers and the second option allocates wavelengths of 1550 to 1560 nanometers. Optical coupler140will be described below as complying with G.983.3; however, optical coupler140need not comply with G.983.3 but may use any allocation of wavelengths.

Second port142of optical coupler140receives a first optical signal and transmits the first optical signal to first port141with limited signal loss (e.g., the signal loss may be less 2 dB or may be less than 1 dB). Alternatively, the first optical signal is transmitted to first port141with substantially no signal loss. The first optical signal may be a test signal from optical time domain reflectometer150. Optical coupler140may use wave division multiplexing to transmit the first optical signal to end user port141. In this manner, the test signal is carried on its own wavelength and does not interfere with other signals. Since G.983.3 does not allocate a wavelength band for test signals, any test signal wavelength may be used, such as for example, 1610 nanometers. With such a test signal wavelength, optical coupler140may be adapted so that wavelengths of about 1610 nanometers are transmitted to first port141with limited signal loss. Any wavelength can be used but typically a wavelength that does not interfere with other signals is used.

Once the test signal is reflected back (e.g., from computer194or from other optical connectors) to optical coupler140, first port141may receive test signal. In more detail, first port141receives the reflected test optical signal (e.g., a series of optical pulses having a wavelength of 1610 nanometers) from first port141. Optical coupler140may use wave division de-multiplexing to transmit the test optical signal to second port142with limited signal loss (e.g., the signal loss may be less 2 dB or may be less than 1 dB). Alternatively, the test optical signal is transmitted to second port142with substantially no signal loss. Therefore, optical coupler140may be adapted so that test optical signals received at first port141having a wavelength of about 1610 nanometers are transmitted to second port142with limited signal loss. In this manner, optical time domain reflectometer150may receive the test signal as if it were connected directly to the fiber optic network connection being tested.

Third port143receives a second optical signal and transmits the second optical signal to first port141with limited signal loss (e.g., the signal loss may be less 2 dB or may be less than 1 dB). Alternatively, the second optical signal is transmitted to first port141with substantially no signal loss. The second optical signal may be a data signal from data optical line termination120. Optical coupler140may use wave division multiplexing to transmit the second optical signal to first port141. G.983.3 allocates a wavelength band for data signals of 1480 to 1500 nanometers. Therefore, optical coupler140may be adapted so that optical signals having a wavelength of about 1480 to about 1500 nanometers are transmitted to first port141with limited signal loss. In this manner, the data signal is carried on its own wavelength and does not interfere with other signals.

Fourth port144receives a third optical signal and transmits the third optical signal to first port141with limited signal loss (e.g., the signal loss may be less 2 dB or may be less than 1 dB). Alternatively, the third optical signal is transmitted to first port141with substantially no signal loss. The third optical signal may be a video signal from video optical line termination120. Optical coupler140may use wave division multiplexing to transmit the third optical signal to first port141. G.983.3 allocates a wavelength band for data signals of 1539 to 1565 nanometers for the enhancement band. Therefore, optical coupler140may be adapted so that optical signals having a wavelength of about 1540 to about 1560 nanometers are transmitted to first port141with limited signal loss. In this manner, the video signal is carried on its own wavelength and does not interfere with other signals.

Optical coupler140may also receive a fourth optical signal from first port141. The fourth optical signal may be a data signal from computer194. Optical coupler140may use wave division de-multiplexing to transmit the fourth optical signal to third port143with limited signal loss with limited signal loss (e.g., the signal loss may be less 2 dB or may be less than 1 dB). Alternatively, the fourth optical signal is transmitted to third port143with substantially no signal loss. G.983.3 allocates a wavelength band for data signals of 1260 to 1360 nanometers for such signals. Therefore, optical coupler140may be adapted so that optical signals received at first port141having a wavelength of about 1260 to about 1360 nanometers are transmitted to third port143with limited signal loss.

As can be seen, optical coupler140provides a device that can multiplex optical signals and can also provide for optical testing without disrupting data and video signal communication. That is, optical time domain reflectometer150may be connected to a test port (e.g., second port142) of optical coupler140for testing of the network connection. To make such connection simple, optical coupler140may also comprise connectors to facilitate installation and testing.FIG. 3shows optical coupler140including illustrative connectors. As shown inFIG. 3, first port141comprises a first optical connector341, second port142comprises a second optical connector342, third port143comprises a third optical connector343, and fourth port144comprises a fourth optical connector344. Optical connectors341,342,343, and344may be mounted to a substrate300. Substrate300may be a printed circuit board, a card, or the like. Optical connectors341,342,343, and344may comprise a SC type connector, a ST type connector, a FC type connector, or the like.

FIG. 4shows an alternative illustrative optical coupler140′ including pigtail type connections. A pigtail type connection is a short length of jacketed fiber optic permanently fixed to a component or substrate at one end and a connectorized termination at the other end. As shown inFIG. 4, first port141comprises a first optical connector341connected to a substrate400via a pigtail connection410, second port142comprises a second optical connector342connected to a substrate400via a pigtail connection410, third port143comprises a third optical connector343connected to a substrate400via a pigtail connection410, and fourth port144comprises a fourth optical connector344connected to a substrate400via a pigtail connection410.

FIG. 5ashows another alternative illustrative optical coupler140″ including a modular housing. As shown inFIG. 5a, optical connectors341,342,343, and344are mounted to a face of housing500. Housing500may be a modular housing and may be adapted to be rack mounted, panel mounted, and the like. With such modularity, housings500may be more easily installed and removed from a cabling enclosure (not shown), thereby providing for maintenance, replacement, and expansion.

FIG. 5bshows yet another illustrative optical coupler140′″ including a housing510for receiving multiple optical couplers. As shown inFIG. 5b, housing510houses three optical couplers, however, any number is possible.

It is noted that the foregoing description has been provided merely for the purpose of explanation and is in no way to be construed as limiting of the invention. While the invention has been described with reference to illustrative embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Further, although the invention has been described herein with reference to particular structure, methods, and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all structures, methods and uses that are within the scope of the appended claims. Those skilled in the art, having the benefit of the teachings of this specification, may effect numerous modifications thereto and changes may be made without departing from the scope and spirit of the invention, as defined by the appended claims.