Patent Application
20060239691
In recent years, there have been a concerted efforts by communications networks service providers to improve speeds of the “last mile” in communications networks. The “last mile” generally refers to the link from a Central Office (CO) of a communications network to a subscriber site, such as a personal residence or business facility. Improvements are being made to increase the speed by replacing wired telephony lines, which support limited bandwidth, with broadband communications cables or even fiber optic communications cables.
Communications Network Terminals (NT's) are typically found at each subscriber site and may include one or more technologies for converting high data rate signals to lower data rate signals that subscriber equipment, such as Personal Computers (PC's), can use for supporting communications. For example, the network terminals may include optical transceivers with optical-to-electrical converters that convert high-speed optical communications signals to electrical communications signals and vice versa to enable the subscriber equipment to communicate via optical networks.
The principles of the present invention may be applied to an optical transceiver. The optical transceiver may include a housing that supports an optical transmitter and optical receiver. The optical transceiver may also include an optical connector in mechanical contact with the housing. The optical connector is adapted to mate with an optical connector associated with an optical fiber, which supports optical signal transmissions in a fiber optic drop cable between the optical transceiver's (i.e., proximal) transmitter and receiver and a distal optical transmitter and receiver located at a far end of the optical fiber.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
A description of preferred embodiments of the invention follows.
The principles of the present invention provide cost reduction apparatus and method for connecting an optical fiber drop cable to an optical transceiver. In one embodiment, the optical transceiver includes a captive fiber mechanical receptacle (i.e., connector) that is adapted to connect with a connector at the end of an optical fiber. The cost reduction comes into play by obviating need for components that are presently used with each optical transceiver and labor and materials associated with their usage. Through use of an optical transceiver embodiment as disclosed herein, technicians installing optical fibers in, for example, the “last mile” using a fiber optic drop cable of a communications network save time and reduce potentially damaging processes associated with cleaning fiber ends.
The term fiber optic “drop” cable used herein indicates a fiber optic cable that is used in a fiber optic communications application having relatively high power optical transmissions, carried by fiber optic cables, that are highly sensitive to alignment errors in optical connectors that are used to link optical fibers together or to transmitter/receiver components. An example in which a drop cable is used is a home or office fiber optic drop cable link between a Central Office (CO) Optical Link Terminal (OLT) and home or office Optical Network Terminal (ONT) providing optical-to-electrical conversion for converting optical signals to Radio Frequency (RF) electrical signals for use by, for example, cable televisions, which is the reason for the high power optical signals. Examples of “enterprise” applications in which fiber optic cable communications carry low optical power signals carrying digital data and are thus less sensistive to connector alignment errors are office routers and long haul systems, where the term fiber optic “drop” cable as used herein does not generally apply to these low power applications.
For example, in current Broadband Passive Optical Network (BPON) Optical Network Terminal (ONT) technology with video overlay, prior art optical transceivers in the ONT have a fiber pigtail to ensure optical alignment between the fiber optic cable and optical devices in the optical transceivers. The pigtail ends with an SC optical connector. This connector is put into an optical adapter, which is typically a dual female connector, to connect the pigtail to another special captive SC optical connector on the end of a fiber optic cable.
Through use of an optical transceiver according to the principles of the present invention, the fiber optic drop cable can be connected directly to the optical transceiver, which removes (i) the optical adapter and (ii) a need for a “pigtail” on the optical transceiver. The captive receptacle on the optical transceiver facilitates a rugged fiber optic cable and connector assembly. The rugged assembly reduces a cost of the optical transceiver in an ONT because the traditional pigtail fiber and connector is no longer necessary. Also, manual operations for integrating a pigtail are no longer necessary to be done by the manufacturer. Furthermore, the captive receptacle solution renders a need to clean the fiber pigtail at the factory and in the field unnecessary, thus reducing operating costs.
The output of the WDM 140 is connected to splitters 150 in the client subnetwork 115 of the network 100 via the fiber optic cables 145. The splitters 150 separate optical communications into subchannel communications for delivery to and receipt from subscriber sites 155, such as residences and business facilities. Optical communications may use Wavelength Division Multiplexing (WDM), Time Division Multiplexing (TDM), or other communications protocol(s) supporting multiple subscribers or network access points.
Continuing to refer to
Each OLT 135 in the CO 125, which may contain more than one OLT 135, connects to up to thirty-two Optical Network Terminals (ONT), not shown here but shown in detail in
An ONT is placed at each subscriber site (i.e., home or office) 155. It may be placed indoors, such as in a utility closet, or it may be mounted on the side of the subscriber site 155 where it may be mounted inside a secure, weather-proof housing 203, sometimes referred to as a Network Interface Device (NID) enclosure 203.
The actual optical fiber in the fiber optic cable 145 is extremely small in diameter, about the diameter of a human hair, and is very fragile. For ease of use and protection, the optical fiber is wrapped in multiple layers of protective material whose diameter varies depending on the intended usage. For use in the outdoors, the fiber optic cable 145 is several inches in diameter. As it nears its intended destination, layers of material are removed to make it smaller and easier with which to work.
As indicated in
The fiber 145 from the OLT 135 is generally much larger due to its protective covering and terminates in an optical connector 312a, which is connected to a heavy duty, double-sided, female connector 310a held in the mounting plate 311a. The prior art embodiment of
The triplexer 300 terminates the optical signals from the OLT 135 and converts them to electrical signals. The triplexer 300 also converts electrical signals from the ONT 200 into corresponding optical signals and sends the optical signals towards the OLT 135 across the fiber optic cable 145. The triplexer 300 is one of the most costly components in the ONT 200.
The prior art topology described above requires two male connectors 308 and 312a, one double-sided female connector 310a, a mounting plate 311a, and a pigtail 305 to connect the fiber 145 from the OLT 135 to the triplexer 300 in the ONT 200. This arrangement includes extensive material, manual operations, and costs. Reliability is reduced because there are multiple places where components can be broken, misaligned, or improperly cleaned.
The distinction between
In the embodiment of
The principles of the present invention reduce costs and labor associated with the “pigtail” configuration by eliminating the double-sided female connector 310a or 310b and its mounting plate 311a or 311b, respectively, the pigtail 305 and its male connector 308, and multiple manual alignment, cleaning, and installation operations.
There are several embodiments in which the housing 402 and connector 405a can be associated. For example, the housing 402 and connector 405a may be integrated during manufacturing of the housing 402, such as cast as a single unit. In another embodiment, the connector 405a can be attached, affixed, secured, inserted, press fit, adhered, or otherwise connected to the housing 402 after the housing is formed. It should be understood that any form of mechanical connection between the housing 402 and connector 405a can be employed during manufacturing or assembly processes of the transceiver 400.
The connector 405a preferably includes a form of strain relief. For example, in
The transmitter 545 is connected to an electro-optic device 535, such as a laser diode, and the receivers 550 are electrically connected to optoelectronic devices 540, which may be silicon-based devices or other devices used to receive optical signals and convert them into electrical signals, as well known in the art. The electro-optic device 535 and optoelectronic devices 540 may be mechanically arranged in various ways relative to the connector 405a to enable optical coupling with an optical fiber 525 in the fiber optic cable 145.
The male connector 405b is illustrated at an end of the fiber optic cable 145. Inside the fiber optic cable is the fiber optic 525 through which optical transmissions travel. At the end of the fiber optic 525, in some embodiments, the fiber optic 525 expands in a bell shape 530 and connects to a small lens assembly 520 to enable optical signals to be transmitted into and out of the optical fiber 525 with maximum optical insertion/extraction. In other embodiments, other optical insertion/extraction techniques are employed. It should be understood that the optical coupling techniques employed are relatively unimportant for an understanding of the principles of the present invention, although choice of connector 405a, 405b must be suitable for optical interfacing between optical devices 535, 540 and optical fiber assemblies 520, 535, 530 or the like. Note that the optical insertion/extraction techniques disclosed herein are simplistic and are in no way intended to limit the scope of the present invention.
Through this configuration, the transmitters 545 and receivers 550 supported by the housing 400, which may be referred to as proximal transmitters and receivers, communicate with distal transmitters and receivers (not shown), such as at the OLT 135, via optical signal transmissions supported by the optical fiber 525.
As described above, the housing 400 is associated with the connector 405a. In the embodiment of
The connector 405a may also include stops 512, which may serve as hermetic seals when the male connector 405b is fully engaged with the female connector 405a. The female connector 405a and male connector 405b may include polarization keys 515a and 515b, which ensure that the connectors 405a and 405b are mated with a particular polarity to ensure optical signals transmitted via the optical fiber 525 are communicated with correct polarity or orientation between transmitters and receivers.
It should be understood that, although illustrated as a female connector 405a on the transceiver 400, another embodiment may use a male connector 405a associated with the transceiver 400, in which case, the connector 405b on the fiber optic cable 145 is a female connector 405b. However, because most systems existing in the field use male connectors at the ONT-end of the fiber optic cables 145, a female connector 405a associated with the transceiver 400 is preferable to support legacy installations. Also, the connector 405a may be designed to mate with the connector 312 used in existing installations and provide sufficient strain relieving. Alternatively, the connectors 405a and 405b may be selected for new ONT deployments without concern for legacy installations.
The transceiver 400, connectors 405a and 405b, fiber optic cable 145, and other associated components are sometimes referred to as a “drop cable assembly.” A technician or other personnel may assemble a drop cable assembly by inserting the cable connector 405b into the transceiver connector 405a in a manner described above. It should be understood that a transceiver manufacturer or transceiver housing manufacturer can manufacture the transceiver housing 402 with transceiver connector 405a in any manner known in the art, including through custom techniques.
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
For example, although the principles of the present invention are described in reference to an optical transceiver, they equally apply to other optical devices in which a pigtail or other fiber optic cable and adapter connector arrangement to the optical device can directly be replaced with a simpler connector arrangement as described herein. Similarly, the principles of the present invention may be equally applied to electrical, acoustical, microwave, or other electromagnetic wave devices.
The optical transceivers employing the principles of the present invention are described herein as being applied for use at the subscriber sites 155; however, it should be understood that optical transceivers may be used wherever advantages as described herein may be leveraged.
