System and method for distributing optical signals

An optical signal distribution system is provided herein useful for multiple service operators (MSOs) in providing content data to subscribers, and receiving control and other data from subscribers. The system facilitates the transmission of content data to the subscribers and the control and other data from subscribers substantially in the optical domain. The system includes a head-end configured to transmit the content data via a forward channel optical signal and receive the control data via a composite reverse channel optical signal. The system also includes a signal distribution hub configured to receive and replicate the forward channel optical signal for transmission to optical taps, receive reverse channel optical signals from the optical taps, generate a composite reverse channel optical signal, and transmit the composite reverse channel optical signal. Each optical tap sends and receives the forward and reverse channel optical signals to and from a plurality of subscribers units.

FIELD

The present disclosure relates generally to optical systems, units and components, and in particular, to a system and method for distributing optical signals.

BACKGROUND

Multiple system operators (MSOs), such as cable companies, typically provide content data to many subscribers. For example, MSOs typically provide video/audio, in the form of movies or television content, to subscribers via a digital communication network. Similarly, MSOs also provide audio only, such as piped music, to subscribers via such digital communication network. Other content data provided by MSOs to subscribers include internet data (e.g., HTML documents, email, and other internet data), emergency and alert information originating from local or national government agencies, and other types of data.

As mentioned above, MSOs typically use a digital communication network to provide content data to subscribers via a forward channel, and also receive control and other data from subscribers via a reverse channel. For example, the control and other data sent from subscribers to MSOs typically include orders for particular content, such as a movie, internet data, such as a request (e.g., URL) for a particular HTML document, or an email destined for a particular recipient. In the past, MSOs have employed hybrid fiber-coaxial (HFC) type digital communication network to facilitate the communication of data between MSOs and subscribers.

A typical HFC digital communication network consists of a head-end, one or more hubs coupled to the head end, and a plurality of taps coupled to each of the one or more hubs. The head-end provides the source of the content data for subscribers, and also receives and processes the control and other data from subscribers. The head-end is communicatively coupled to each hub by way of an optical fiber network, where data is communicated between the head-end and the hubs in the optical domain. Each hub serves as a node for routing content data to subscribers within a defined geographical area, and routing control and other data from such subscribers to the head-end. Each hub is coupled to a plurality of taps by way of an electrical network, where data is communicated between the hub and the taps in the electrical domain, such as by radio frequency (RF) signals. Each subscriber unit within the geographical area is coupled to one of the plurality of taps via an electrical connection.

An HFC digital communication network has several drawbacks. First, the electrical communication network between the hubs and the subscribers has limited bandwidth. Thus, as a result, the number of subscribers that can be serviced by a single hub is relatively limited. Additionally, the limited bandwidth further limits the amount of content channels available for subscribers in the forward direction, as well as the upload capability for subscribers in the reverse direction. Moreover, the power required to operate the electrical communication network is relatively large, and thus, expensive to operate for MSOs.

SUMMARY

An aspect of the disclosure relates to an optical signal distribution system that may be useful to MSOs in providing content data to subscribers and receiving control and other data from subscribers. The optical signal distribution system is configured to deliver the content data to subscribers and receive the control and other data from subscribers substantially by way of optical signals or in the optical domain.

This overcomes many of the drawbacks of HFC digital communication systems or networks. For instance, the optical signal distribution system is capable of higher bandwidth due to the communications being substantially in the optical domain. This enables MSOs to service greater number of subscribers. It also allows MSOs to offer more channels for subscribers, thereby providing more options and a better entertainment experience for subscribers. Additionally, the signally being in the optical domain enables MSOs to operate their systems with substantially less power, thereby potentially reducing costs and increasing revenues for MSOs. The reduction in power consumption also provides the environmental benefits.

More specifically, the optical signal distribution system comprises a head-end, a signal distribution hub, a plurality of optical taps, and a plurality of subscriber units. The head-end comprises a source of the content data for subscribers and a sink (e.g., a data processing unit) for the control and other data from the subscribers. The content data may include movies, television programs, audio, alert and emergency information, internet data, and other types of content data. The control and other data may include requests or orders for movies, subscription changes, requests for internet data (e.g., URL), emails, etc. The head-end comprises an optical transmitter for generating and transmitting a forward channel optical signal including the content data to the signal distribution hub for subsequent delivery to subscribers. The head-end further comprises an optical receiver for receiving a composite reverse channel optical signal from the signal distribution hub, and extracting the subscriber control and other data from the signal.

The optical signal distribution system further comprises one or more optical communication mediums, such as one or more optical fibers which may also include one or more optical ring resonators, coupling the head-end to the signal distribution hub. In one embodiment, one or more optical communication mediums may be configured to facilitate transmission of the forward channel optical signal, and another one or more optical communication mediums may be configured to facilitate transmission of the composite reverse channel optical signal. In another embodiment, the same one or more optical communication mediums may serve to facilitate the transmission of both the forward channel optical signal and the composite reverse channel optical signal. In the latter case, the head-end may further comprise a wavelength-division multiplexer (WDM) to transmit and receive the forward and reverse channel signals to and from the same optical communication medium.

The signal distribution hub is configured to receive the forward channel optical signal from the head-end, amplify and split the forward signal to generate a plurality of forward channel optical signals, and transmit the plurality of forward channel optical signals to the optical taps by way of a plurality of optical communication mediums, respectively. Additionally, the signal distribution hub is further configured to receive a plurality of reverse channel optical signals from the optical taps by way of the plurality of optical signals, respectively. The signal distribution hub is further configured generate one or more composite reverse channel optical signals based on the plurality of reverse channel optical signals. The signal distribution hub is configured to transmit the one or more composite reverse channel optical signals to the head-end.

With respect to components, the signal distribution hub comprises an optical amplifier, such as an erbium doped fiber amplifier (EDFA), configured to amplify the forward channel optical signal. The signal distribution hub further comprises an optical distribution assembly comprising a splitter configured to split the amplified forward channel optical signal into a plurality of forward channel optical signals. Additionally, the optical distribution assembly comprises a plurality of wavelength-division multiplexers (WDMs) configured to multiplex the plurality of forward channel optical signals onto respective optical communication mediums for transmission to the respective optical taps, and de-multiplex the reverse channel optical signals from the respective optical communication mediums. The signal distribution hub further comprises a return transmitter module adapted to generate the one or more composite reverse channel optical signals for transmission to the head-end.

In one embodiment, the return transmitter module comprises a plurality of optical receivers configured to generate electrical signals from the reverse channel optical signals, respectively. The return transmitter module further comprises a combiner configured to combine the electrical signals to generate a composite electrical signal. Additionally, the return transmitter module comprises an optical transmitter configured to generate a composite reverse channel optical signal, based on the composite electrical signal, for transmission to the head-end.

In another embodiment, the return transmitter module comprises a plurality of optical receivers configured to generate electrical signals from the reverse channel optical signals, respectively. The return transmitter module further comprises a first combiner configured to combine a first subset of the electrical signals to generate a first composite electrical signal. The return transmitter module further comprises a second combiner configured to combine a second subset of the electrical signals to generate a second composite electrical signal. Additionally, the return transmitter module comprises first and second optical transmitters configured to generate first and second composite reverse channel optical signals, based on respectively the first and second composite electrical signals, for transmission to the head-end. The return transmitter module may further comprise a wavelength-division multiplexer (WDM) configured to multiplex the first and second composite reverse channel optical signals onto the same optical communication medium for transmission to the head-end.

Each optical tap may be coupled to a plurality of subscriber units by way of a plurality of optical communication mediums, respectively. As an example, the signal distribution hub may be coupled to eight optical taps, and each optical tap may be coupled to 32 subscriber units. Thus, in this example, the signal distribution hub may service up to 256 subscribers. Additionally, the signal distribution hub may be configured with a plurality of optical distribution assemblies for servicing much higher number of subscribers. Accordingly, such signal distribution hub may be easily expandable for servicing more subscribers in response to growing customers in a defined geographical area.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1illustrates a block diagram of an exemplary optical signal distribution system100for distributing optical signals in accordance with an aspect of the disclosure. An objective of the exemplary optical signal distribution system100is to communicate data between a head-end or source of content data and a plurality of subscribers substantially in the optical domain. Providing signaling between the head-end and subscribers substantially in the optical domain has many advantages over prior HFC communication systems.

First, the optical signal distribution system100is capable of bandwidths substantially higher that can be achieved by HFC systems. This allows for a single hub to service more subscribers, which translates to more revenue for MSOs. Further, the higher bandwidth allows for substantially more channels to be provided to subscribers, thereby providing subscribers with more entertainment options. Additionally, the higher bandwidth provides subscribers improved speed for downloading and uploading internet data. Second, the optical signal distribution system100is capable of substantial reduction in the amount of power consumed in operating the system. This translates to increase revenue for MSOs, as well as having beneficial consequences for the environment.

In particular, the optical signal distribution system100comprises a head-end110, a signal distribution hub130, a plurality of optical taps150-1to150-8, and a plurality of subscriber units170-1to170-256. The optical signal distribution system100further comprises an optical communication medium120(e.g., one or more optical fibers) for routing optical signals λfin a forward direction (towards the subscribers) from the head-end110to the signal distribution hub130. The optical communication medium120may include one or more optical ring resonators. Additionally, the optical signal distribution system100comprises another optical communication medium122(e.g., one or more optical fibers) for routing optical signals λrcin a reverse direction (towards the head-end) from the signal distribution hub130to the head-end110. Similarly, the optical communication medium122may include one or more optical ring resonators.

The optical signal distribution system100further comprises a plurality of optical communication mediums140-1to140-8for routing optical signals λfand λrin the forward and reverse directions between the signal distribution hub130and the optical taps150-1to150-8, respectively. As shown, each of the optical communication mediums140-1to140-8may include an optical ring resonator. Although, in this example, there are eight (8) optical taps150-1to150-8, it shall be understood that the optical signal distribution system100may include any number of optical taps coupled to the signal distribution hub130. And, the number of optical communication mediums coupling the signal distribution hub to the optical taps may vary accordingly.

The optical signal distribution system100further a plurality of sets of optical communication mediums (e.g., one or more optical fibers) coupling the optical taps150-1to150-8to sets of subscriber units170-1to170-32,170-33to170-64,170-65to170-96,170-97to170-128,170-129to170-160,170-161to170-192,170-193to170-224, and170-225to170-256, respectively. Although, in this example, there are 32 subscriber units assigned or coupled to each optical tap, it shall be understood that the optical signal distribution system100may include any number of subscriber units assigned or coupled to a single optical tap. And, the number of optical communication mediums coupling each optical tap to the corresponding subscriber units may vary accordingly.

In this example, the head-end110comprises a data source112, an optical transmitter (Tx)114, an optical receiver (Rx)116, and a data sink118. The data source112includes content data for transmission to the subscribers. The data source112may, in turn, receive content data from external sources, such as by a satellite link, a wide area network (WAN), such as the Internet, and from other external sources. The data source112provides the content data to the optical transmitter114to generate an optical signal λfwhich includes the content data. Pursuant to many data transmission techniques, the content data may undergo any one or more of the following: error encoding, channel encoding, encrypting, interlacing, constellation symbol modulation, RF modulation, other processing, and optical signal modulation to generate the forward channel optical signal λfcomprising the content data. It shall be understood that the optical signal λfmay comprise one or more distinct wavelengths.

The optical receiver116receives an optical signal λrc, which as discussed in more detail herein, may be a combination or composite of optical signals λrgenerated at one or more respective subscriber units170-1to170-256. Pursuant to many data reception techniques, the received signal λrcmay undergo one or more of the following: optical demodulation, RF demodulation, constellation symbol demodulation, de-interlacing, decrypting, channel decoding, error decoding, and other signal processing to generate the control and other data from the subscribers. The optical receiver116provides the control and other data to the data sink118. The data sink118processes the control and other data. As previously discussed, the control data may specify an order from a subscriber for a particular content, such as a movie, or a request for internet data (HTML, email, etc.). In response, the data sink118instructs the data source112to provide the appropriate content to the subscribers based on the received control data. Additionally, the other data from subscriber may include emails, which the data sink118transmits via a wide area network (WAN), such as the Internet.

FIG. 2Aillustrates a block diagram of an exemplary signal distribution hub200in accordance with another aspect of the disclosure. The signal distribution hub200may be a detailed implementation of the signal distribution hub130, previously discussed. In summary, the signal distribution hub200receives the forward channel optical signal λffrom the head-end110via the optical communication medium120, amplifies and splits the forward optical signal λfto generate eight (8) forward channel optical signals λf, and transmits the eight (8) forward channel optical signals λfto the optical taps150-1to150-8by way of the optical communication mediums140-1to140-8, respectively. The signal distribution hub200also receives the reverse channel optical signals λrfrom the subscriber units by way of the optical communication mediums140-1to140-8, combines the reverse channel optical signals λrto form one or more composite reverse channel optical signals λrc, and transmits the one or more composite reverse channel optical signals λrcto the head-end110by way of the optical communication medium122.

In more detail, the signal distribution hub200comprises an optical amplifier220, an optical distribution assembly (ODA)230, and a return transmitter module (RTM)240, all of which may be situated within a housing210. The optical amplifier220receives the forward channel optical signal λffrom the head-end110by way of the optical communication medium120, and amplifies the optical signal λfin the optical domain. The amplified optical signal λfis routed from the optical amplifier220to the ODA230. The ODA230splits the forward channel optical signal λfto form eight (8) replicas of the optical signal λf, and transmits the replicas λfto the optical taps150-1to150-8by way of optical communication mediums140-1to140-8, respectively.

The ODA230also receives the reverse channel optical signals λrfrom the optical taps150-1to150-8by way of the optical communication mediums140-1to140-8, respectively. The ODA230directs the reverse channel optical signals λrto the RTM240. The RTM240, in turn, combines the reverse channel optical signals λrto form the composite reverse channel optical signal λrc. The RTM240then transmits the composite reverse channel optical signal λrcto the head-end110by way of optical communication medium122.

FIG. 2Billustrates a block diagram of another exemplary signal distribution hub250in accordance with another aspect of the disclosure. The signal distribution hub250is similar to signal distribution hub200previously discussed, and includes some of the same components as indicated by the same reference numbers. In contrast, the signal distribution hub250includes a modified RTM242and a wavelength-division multiplexer (WDM)244.

In this example, the RTM242generates a pair of composite reverse channel optical signals λrc1and λrc2, wherein composite optical signal λrc1is based on a first distinct set of the reverse channel optical signals λrand composite optical signal λrc2is based on a second distinct set of the reverse channel optical signals λr. It shall be understood that the RTM242may generate any number of composite optical signals from any sets of the reverse channel optical signals. The WDM244multiplexes the composite reverse channel optical signals λrc1and λrc2onto the optical communication medium122for transmission to the head-end110.

FIG. 3illustrates a block diagram of an exemplary optical amplifier300in accordance with another aspect of the disclosure. The optical amplifier300may be an exemplary detailed implementation of the optical amplifier220previously discussed. As indicated, the optical amplifier220amplifies the forward channel optical signal λfin the optical domain. The optical amplifier300comprises an input tap302, an input detector304, an isolator306, a gain medium308, an optical pump310, an optical ring resonator312, an output tap/isolator314, an output detector316, and a microcontroller320.

The input tap302receives the forward channel optical signal λffrom the head-end110by way of the optical communication medium120, couples off a relatively small portion of the optical signal for the input detector304, and forwards the remainder to the isolator306. The input detector304generates an electrical signal based on the input optical signal, and may digitize the electrical signal for processing by the microcontroller320. The optical signal λfforwarded by the input tap302is applied to the gain medium308by way of the isolator306. The gain medium308combines the optical signal λfwith a pump optical signal λpgenerated by the optical pump310to amplify the optical signal λf. As an example, the gain medium308may comprise an erbium-doped fiber. Other types of gain mediums may be used.

The amplified forward channel optical signal λfis then pass through the optical ring resonator312, which operates to remove or filter remnants of the optical pump signal and other unwanted optical components from the amplified optical signal. The output tap isolator314couples off a relatively small portion of the amplified and filtered optical signal λffor the output detector316, and outputs the remainder portion of the amplified and filtered optical signal λf. The output detector316generates an electrical signal based on the output optical signal, and may digitize the electrical signal for processing by the microcontroller320. The microcontroller320controls the optical pump310, and in particular, the power level of the optical pump signal λpbased on the electrical signals from the input and output detectors304and316in order to achieve a defined gain for the forward channel optical signal λf.

FIG. 4illustrates a block diagram of an exemplary optical distribution assembly (ODA)400in accordance with another aspect of the disclosure. The ODA400may be an exemplary detailed implementation of the ODA230previously discussed. As previously discussed, the ODA400receives the amplified forward channel optical signal λf, splits the optical signal λfto generate a plurality (e.g., eight (8)) replica optical signals λf, and transmits the replica optical signals λfby way of optical communication mediums140-1to140-8, respectively. Additionally, the ODA400receives the reverse channel optical signals λfby way of the optical communication mediums140-1to140-8, respectively, and provides the signals λrto the RTM.

More specifically, the ODA400comprises a splitter402, and a plurality (e.g., eight (8)) wavelength-division multiplexers (WDMs)404-1to404-8. The splitter402receives the amplified forward channel optical signal λf, and splits the signal to form eight (8) replica optical signals λf. The eight (8) WDM404-1to404-8receive and multiplexe the eight (8) replica optical signals λfonto the optical communication mediums140-1to140-8, respectively. The eight (8) WDM404-1to404-8also de-multiplexes the eight (8) reverse channel optical signals λrfrom the optical communication mediums140-1to140-8, respectively. Thus, the optical communication mediums140-1to140-8are used for simultaneous transmission of the forward and reverse channel optical signals λfand λr, both having distinct wavelengths. As previously discussed, the de-multiplexed reverse channel optical signals λrare provided to the RTM for combining and forming one or more composite reverse channel optical signals λrc.

FIG. 5Aillustrates a block diagram of an exemplary return transmitter module (RTM)500in accordance with another aspect of the disclosure. The RTM500may be an exemplary detailed implementation of the RTM240previously discussed. In summary, the RTM240forms a composite optical signal λrcfrom the reverse channel optical signals λrprovided by the ODA. The RTM240may accomplish this by converting the reverse channel optical signals λrinto corresponding electrical signals Er, combining the electrical signals Erto form a composite electrical signal Erc, and modulates an optical carrier with the composite electrical signal Ercto form the composite reverse channel optical signal λrc.

More specifically, the RTM500comprises a plurality of optical receivers502-1to502-8, a combiner504, an optical transmitter506, and a controller508. The optical receivers502-1to502-8receive the reverse channel optical signals λrfrom the ODA, and generate corresponding electrical signals Erby demodulating the reverse channel optical signals λr, respectively. The electrical signals Ermay be RF signals in distinct frequency bands. The combiner504combines the electrical signals Erto form a composite electrical signal Erc. For example, the combiner504may simply add the electrical signals Er, or time-multiplex the signals Er, or frequency-multiplex the signals Er, or code-division multiplex the signals Er, or perform other types of techniques to combine the signals Erto generate the composite electrical signal Erc.

The optical transmitter506then modulates the composite electrical signal Erconto an optical carrier to form the composite reverse channel optical signal λrc. The output of the optical transmitter506may be coupled to the optical communication medium122for transmission of the composite reverse channel optical signal to the head-end110. The controller508monitors the status of the various components in order to generate an indication as to the operational status of the RTM500. For example, the controller508may provide operational status indications, such as no input signal (e.g., by activating a red LED (not shown)), input signal power level low (e.g., below a threshold power level) (e.g., by activating a yellow LED (not shown)), and input signal power level within specification (e.g., by activating a green LED (not shown)).

FIG. 5Billustrates a block diagram of another exemplary return transmitter module (RTM)550in accordance with another aspect of the disclosure. The RTM550is similar to RTM500previously discussed, and includes many of the same elements as indicated by the same reference numbers. The RTM550differs from RTM500in that it generates a plurality of composite reverse channel optical signals based on distinct sets of the reverse channel optical signals λr. In this example, the RTM500generates a first composite optical signal λrc1based on the reverse channel optical signals λrapplied to optical receivers502-1to502-4, and a second composite optical signal λrc2based on the reverse channel optical signals λrapplied to optical receivers502-5to502-8.

More specifically, the RTM550comprises a plurality (e.g., eight (8)) optical receivers502-1to502-8, a plurality (e.g., two (2)) of combiners504-1and504-2, a plurality (e.g., two (2)) of optical transmitters506-1and506-2, and a wavelength-division multiplexer (WDM)510. The optical receivers502-1to502-8receive the reverse channel optical signals λrfrom the ODA, and generate corresponding electrical signals Erby demodulating the reverse channel optical signals λr, respectively. A first set of the electrical signals Ergenerated by the optical receivers502-1to502-4are applied to respective inputs of combiner504-1. Similarly, a second set of the electrical signals Ergenerated by the optical receivers502-5to502-8are applied to respective inputs of combiner504-2.

The combiners504-1and502combine the first and second sets of electrical signals Erin accordance with any of the various techniques previously discussed to generate first and second composite electrical signals Erc1and Erc2, respectively. The optical transmitters506-1and506-2modulate the first and second composite electrical signals Erc1and Erc2onto respective optical carriers of distinct wavelengths to generate the first and second composite reverse channel optical signals λrc1and λrc2, respectively. The WDM510multiplexes the first and second reverse channel optical signals λrc1and λrc2onto the optical communication medium122for transmission to the head-end110. As in the previous embodiment, the controller508monitors the components of the RTM550and provides an indication as to their respective operational status.

FIG. 6illustrates a block diagram of another exemplary optical signal distribution system600for distributing optical signals in accordance with an aspect of the disclosure. The optical signal distribution system600is similar to the optical signal distribution system100previously discussed. However, the optical signal distribution system600includes an optical communication medium coupling the head-end to the signal distribution hub, wherein the communication medium facilitates the transmission of both forward channel optical signal λfand the composite reverse channel optical signal λrc.

More specifically, the optical signal distribution system600comprises a head-end610, a signal distribution hub630, a plurality (e.g., eight (8)) optical taps650-1to650-8, and a plurality of subscriber units670-1to670-256. The optical signal distribution system600further comprises an optical communication medium620(e.g., one or more optical fibers) communicatively coupling the head-end610to the signal distribution hub630. As shown, the optical communication medium620may include one or more optical ring resonators.

The optical signal distribution system600further comprises a plurality of optical communication mediums640-1to640-8(e.g., one or more optical fibers) communicatively coupling the signal distribution hub630to the optical taps650-1to650-8, respectively. As shown, each of the optical communication mediums640-1to640-8may include one or more optical ring resonators. Additionally, the optical signal distribution signal600further comprises a plurality of sets of optical communication mediums660(e.g., one or more optical fibers) communicatively coupling the optical taps650-1to650-8to subscriber units670-1to670-32,670-33to670-64,670-65to670-96,670-97to670-128,670-129to670-160,670-161to670-192,670-193to670-224, and670-225to670-256, respectively.

The head-end610of optical signal distribution system600, in turn, comprises a data source612, an optical transmitter614, a wavelength-division multiplexer (WDM)619, an optical receiver616, and a data sink618. Similar to the previous embodiment100, the data source612provides content data for subscribers. The optical transmitter614generates a forward channel optical signal λfwhich carries or includes the content data. The optical receiver616receives the composite reverse channel optical signal λrc, and extracts therefrom the control and other data from the subscribers. And, the data sink618processes the control and other data as previously discussed.

In this case, the WDM619multiplexes the forward channel optical signal λfreceived from the optical transmitter614onto the optical communication medium620for transmission to the signal distribution hub630. The WDM619also de-multiplexes the composite reverse channel optical signal λrcfrom the optical communication medium620and provides it to the optical receiver616. Thus, the use of the WDM619allows for the simultaneous transmission of the forward channel optical signal λfand the composite reverse channel optical signal λrcby way of the optical communication medium620, both signals λfand λrchaving distinct wavelengths.

FIG. 7Aillustrates a block diagram of yet another exemplary signal distribution hub700in accordance with another aspect of the disclosure. The signal distribution hub700may be an exemplary detailed implementation of the signal distribution hub630previously discussed. The signal distribution hub700comprises a bi-directional optical amplifier720, a wavelength-division multiplexer (WDM)725, an optical distribution assembly (ODA)730, and a return transmitter module (RTM)740, all of which may be situated within a housing710.

The bi-directional optical amplifier720receives the forward channel optical signal λffrom the head-end610by way of the optical communication medium620, and amplifies the optical signal λf. The WDM725de-multiplexes the amplified forward channel optical signal λffrom the forward output of the bi-directional optical amplifier720, and provides the amplified signal λfto the ODA730. Similar to previously-discussed ODAs, the ODA730splits the amplified forward channel optical signal λfinto a plurality (e.g., eight (8)) replica signals λf, and multiplexes those signals λfonto optical communication mediums640-1to640-8for transmission to the optical tabs650-1to650-8, respectively.

Similar to the previous embodiments, the ODA730de-multiplexes the reverse channel optical signals λrfrom the respective optical communication mediums640-1to640-8, and provides the reverse channel optical signals λrto the RTM740. Similar to the previous embodiments, the RTM740generates a composite reverse channel optical signal λrcbased on the reverse channel optical signals λr. The WDM725multiplexes the composite reverse channel optical signal λrconto the reverse input of the bi-directional amplifier720. The bi-directional amplifier720amplifies the composite reverse channel optical signal λrc, and provides the amplified optical signal λrcto the optical communication medium620for transmission to the head-end610.

FIG. 7Billustrates a block diagram of still another exemplary signal distribution hub750in accordance with another aspect of the disclosure. The signal distribution hub750is similar to signal distribution hub700previously discussed, and includes several of the same elements as indicated by the same reference numbers. The signal distribution hub750differs from hub700in that it includes an RTM742that generates a plurality (e.g., two (2)) composite reverse channel optical signals λrc1and λrc2based on distinct sets of the reverse channel optical signals λr. Accordingly, the WDM725multiplexes the composite reverse channel optical signals λrc1and λrc2onto the reverse input of the bi-directional amplifier720, which amplifies the signals λrc1and λrc2and couples them to the optical communication medium620for transmission to the head-end610.

FIG. 8illustrates a block diagram of an exemplary bi-directional optical amplifier800in accordance with another aspect of the disclosure. The bi-directional optical amplifier800may be an exemplary detailed implementation of the bi-directional optical amplifier720previously discussed. As indicated, the bi-directional optical amplifier800amplifies the forward channel optical signal λfin the forward direction, and amplifies one or more composite reverse channel optical signals, such as signals λrcor λrc1and λrc2in the reverse direction. The bi-directional optical amplifier800comprises a tap802, a first detector804, an isolator806, a forward channel gain medium808, a forward channel optical pump810, an optical ring resonator812, a reverse channel gain medium814, a reverse channel optical pump816, a tap isolator818, a second detector820, and a microcontroller830.

With regard to amplification in the forward direction, the tap802receives the forward channel optical signal λffrom the head-end610by way of the optical communication medium620, couples off a relatively small portion of the forward optical signal λffor the first detector804, and forwards the remainder to the isolator806. The first detector804generates an electrical signal based on the forward optical signal λf, and may digitize the electrical signal for processing by the microcontroller830. The forward optical signal λfis applied to the gain medium808by way of the isolator806. The gain medium808combines the forward optical signal λfwith a forward channel pump optical signal λfpgenerated by the forward channel optical pump810to amplify the forward channel optical signal λf. As an example, the gain medium908may comprise an erbium-doped fiber. Other types of gain mediums may be used.

The amplified forward channel optical signal λfis then passed through the optical ring resonator812, which operates to remove or filter remnants of the forward optical pump signal λfpand other unwanted optical components from the amplified forward optical signal λf. The tap isolator818couples off a relatively small portion of the amplified forward optical signal λffor the second detector820, and outputs the remainder portion of the amplified forward channel optical signal λf. The second detector820generates an electrical signal based on the forward optical signal λf, and may digitize the electrical signal for processing by the microcontroller830. The microcontroller830controls the forward channel optical pump810, and in particular, the power level of the forward channel optical pump signal λfpbased on the electrical signals from the first and second detectors804and820in order to achieve a defined gain for the forward channel optical signal λf.

The amplification of the composite reverse channel signal λrcor (λrc1and λrc2) operate in a similar manner. The tap isolator818receives the composite reverse channel optical signal λrcor (λrc1and λrc2) from the WDM725, couples off a relatively small portion of the reverse optical signal λrcor (λrc1and λrc2) for the second detector820, and forwards the remainder to the reverse channel gain medium814. The second detector820generates an electrical signal based on the reverse channel optical signal λrcor (λrc1and λrc2), and may digitize the electrical signal for processing by the microcontroller830. The gain medium814combines the reverse channel optical signal λrcor (λrc1and λrc2) with a reverse channel pump optical signal λrpgenerated by the reverse channel optical pump816to amplify the reverse optical signal λrcor (λrc1and λrc2). As an example, the gain medium814may comprise an erbium-doped fiber. Other types of gain mediums may be used.

The amplified reverse channel optical signal λrcor (λrc1and λrc2) is then passed through the optical ring resonator812, which operates to remove or filter remnants of the reverse channel optical pump signal λrpand other unwanted optical components from the amplified reverse channel optical signal λrcor (λrc1and λrc2). The tap802couples off a relatively small portion of the amplified reverse channel optical signal λrcor (λrc1and λrc2) for the first detector804, and provides the remainder portion of the amplified reverse channel optical signal λrcor (λrc1and λrc2) to the optical communication medium620for transmission to the head-end610. The first detector804generates an electrical signal based on the reverse channel optical signal λrcor (λrc1and λrc2), and may digitize the electrical signal for processing by the microcontroller830. The microcontroller830controls the reverse channel optical pump816, and in particular, the power level of the reverse channel optical pump signal λrpbased on the electrical signals from the first and second detectors804and820in order to achieve a defined gain for the reverse channel optical signal λrcor (λrc1and λrc2).

It shall be understood that the forward pump810may be calibrated or adjusted by the microcontroller830when the forward channel optical signal λfis present and the composite reverse channel optical signal λrcor (λrc1and λrc2) is not present. Similarly, it shall be understood that the reverse pump816may be calibrated or adjusted by the microcontroller830when the composite reverse channel optical signal λrcor (λrc1and λrc2) is present and the forward channel optical signal λfis not present. In this way, the microcontroller830is not adjusting the forward pump810based on the composite reverse channel optical signal λrcor (λrc1and λrc2), and not adjusting the reverse pump816based on the forward channel optical signal λf.

FIG. 9Aillustrates a block diagram of an exemplary transceiver900with details on a transmitter portion thereof in accordance with another aspect of the disclosure. The transceiver900may be employed in any of the exemplary head-ends described herein. As previously discussed, the content data sent from the head-end to subscriber units may use one or more wavelengths λf. In the instant example, transceiver900uses three levels of channel modulation to send content data via a plurality of separate channels to subscribers. The first level of channel modulation is in the quadrature amplitude modulation (QAM) domain. The second level of channel modulation is in the frequency division multiplexing (FDM) domain. And, the third level of channel modulation is in the wavelength division multiplexing (WDM) domain.

More specifically, the transceiver900comprises a transmitter910, a receiver920, and a wavelength division multiplexer (WDM)950. InFIG. 9A, the specifics of the transmitter910of the transceiver900are illustrated and described in detail immediately below. However, inFIG. 9A, the receiver920is represented as a dashed block, and the specifics of the receiver920are shown in and described with reference toFIG. 9B. The transmitter910comprises a plurality of QAM modulators912-11to912-NM, a plurality of frequency modulators914-11to914-NM, a plurality of multiplexers916-1to916-N, and a plurality of optical transmitters (or modulators)918-1to918-N. The integer N represents the number of distinct wavelength forward channels used by the transceiver900, and the integer M represents the number of forward frequency channels per each distinct wavelength.

Data pertaining to separate forward channels are applied to the QAM modulators. For instance, data pertaining to forward channels F-111to F-11L are applied to QAM modulator912-11; data pertaining to forward channels F-1M1to F-1ML are applied to QAM modulator912-1M; data pertaining to forward channels F-N11to F-N1L are applied to QAM modulator912-N1; and data pertaining to forward channels F-NM1to F-NML are applied to QAM modulator912-NM. Thus, the integer L represents the number of data channels per QAM modulator. Using this configuration, the variables L, M, and N may be configured to a desired number of data channels, which may be given by L*M*N.

Given the L data channels per each QAM modulator, the output signal of each QAM modulator has 2Lnumber of constellation points. As an example, the number of data channels applied to each QAM modulator could be six (6), which translates to each QAM generating an output signal having 64 constellation points (e.g., 26). As another example, the number of data channels applied to each QAM could be eight (8), which translates to each QAM generating an output signal having 256 constellation points (e.g., 28). The outputs of the QAM modulators are the corresponding data channels in the quadrature amplitude/phase modulation domain. For example, QAM modulator912-11generates QAM channel signal φ11; QAM modulator912-1M generates QAM channel signal φ1M; QAM modulator912-N1generates QAM channel signal φN1; and QAM modulator912-NM generates QAM channel signal φNM.

The quadrature amplitude/phase modulations channel signals from the output of the QAM modulators are applied to frequency modulators, respectively. For instance, QAM channel signal φ11generated by QAM modulator912-11is applied to frequency modulator914-11; QAM channel signal φ1Mgenerated by QAM modulator912-1M is applied frequency modulator914-1M; QAM channel signal φN1generated by QAM modulator912-N1is applied to frequency modulator914-N1; and QAM channel signal φNMgenerated by QAM modulator912-NM is applied to frequency modulator914-NM.

The frequency modulators modulate the quadrature amplitude/phase modulated signals onto respective distinct frequency carriers. For instance, frequency modulator914-11modulates QAM signal φ11onto frequency carrier f11; frequency modulator914-1M modulates QAM signal φ1Monto frequency carrier f1M; frequency modulator914-N1modulates QAM signal φN1onto frequency carrier fN1; and frequency modulator914-NM modulates QAM signal φNMonto frequency carrier fNM. The frequency modulated carriers are applied to the multiplexers, respectively. For instance, the frequency modulated carriers are f11-f1Mapplied to multiplexer916-1, and the frequency modulated carriers fN1-fNMare applied to multiplexer916-N.

The multiplexers combine or multiplex the corresponding frequency modulated carriers to form frequency division multiplex (FDM) signals. For instance, the multiplexer916-1multiplexes the frequency modulated carriers f11to f1Mto form FDM signal f11-f1M. Similarly, the multiplexer916-N multiplexes the frequency modulated carriers fN1to fNMto form FDM signal fN1-fNM. The FDM signals from the outputs of the multiplexers916-1to916-N are applied to the optical transmitters918-1to918-N, respectively.

The optical transmitters modulate the FDM signals from the multiplexers onto optical carriers of distinct wavelengths, respectively. For instance, optical transmitter918-1modulates the FDM signal f11-f1Monto optical carrier λF1, and optical transmitter918-N modulates the FDM signal fN1-fNMonto optical carrier λFN. The modulated optical carriers λF1to λFNare applied to the wavelength division multiplexer (WDM)950which multiplexes the optical carriers onto an optical communication medium (e.g., an optical fiber) to form a WDM forward channel signal λF1-λFNfor transmission to subscriber units. Thus, as exemplified, the transceiver900is capable of very broad bandwidth applications, allowing the transmissions of many data channels using three levels of channel modulation in the: (1) quadrature amplitude/phase domain, (2) frequency division domain, and (3) wavelength division domain.

FIG. 9Billustrates a block diagram of the exemplary transceiver900with details on a receiver portion thereof in accordance with another aspect of the disclosure. As previously discussed,FIG. 9Billustrates the details of the receiver920of the transceiver900, and represents the transmitter910, previously discussed in detail, as a dashed block as shown. Similar to the transmitter910, the receiver920uses three levels of channel demodulation to produce data pertaining to a plurality of reverse channels. The three levels of channel demodulation include: (1) demodulation in the wavelength division domain, (2) demodulation in the frequency division domain, and (3) demodulation in the quadrature amplitude/phase domain.

More specifically, the receiver920comprises a plurality of optical receivers (or demodulators)928-1to928-Q, a plurality of de-multiplexers926-1to926-Q, a plurality of frequency demodulators924-11to924-QP, and a plurality of QAM demodulators922-11to922-QP. The integer Q represents the number of distinct reverse wavelength channels used by the transceiver, and the integer P represents the number of reverse frequency channels per each distinct wavelength.

In addition to transmitting the WDM forward channel signals λF1to λFNvia the optical transmission medium, the WDM950also receives the WDM composite reverse channel signals λRC1to λRCQfrom the optical transmission medium. The WDM950separates or de-multiplexes the signals λRC1to λRCQand applies them to optical receivers928-1to928-Q, respectively. The optical receivers demodulates the WDM composite reverse channel signals to generate FDM composite reverse channel signals, respectively. For instance, optical receiver928-1demodulates WDM composite reverse channel signal λRC1to generate FDM composite reverse channel signal f11-f1P. Similarly, optical receiver928-Q demodulates WDM composite reverse channel signal λRCQto generate FDM reverse channel signal fQ1-fQP. The optical receivers928-1to928-Q apply the FDM composite reverse channel signals f11-f1Pto fQ1-fQPto de-multiplexers926-1to926-Q, respectively.

The de-multiplexers separate or de-multiplexes the FDM composite reverse signals into their respective frequency modulated carriers. For instance, the de-multiplexer926-1separates the FDM composite reverse channel signal f11-f1Pinto frequency modulated carriers f11to f1P. Similarly, the de-multiplexer926-Q separates the FDM composite reverse channel signal f11-f1Pinto frequency modulated carriers fQ1to fQP. The de-multiplexers apply the frequency modulated carriers to respective frequency demodulators. For instance, de-multiplexer926-1applies frequency modulated carriers f11to f1Pto frequency demodulators924-11to924-1P, respectively. Similarly, de-multiplexer926-Q applies frequency modulated carriers fQ1to fQPto frequency demodulators924-Q1to924-QP, respectively.

The frequency demodulators demodulate the respective frequency modulated carriers to generate the quadrature amplitude/phase modulated composite reverse channel signals, respectively. For instance, frequency-demodulator924-11demodulates the frequency modulated carrier f11to generate QAM signal φ11; frequency-demodulator924-1P demodulates the frequency modulated carrier f1Pto generate QAM signal φ1P; frequency-demodulator924-Q1demodulates the frequency modulated carrier fQ1to generate QAM signal φQ1; and frequency-demodulator924-QP demodulates the frequency modulated carrier fQPto generate QAM signal φQP.

The QAM demodulators demodulate the quadrature amplitude/phase modulated signals to generate the reverse channel data. For instance, the QAM demodulator922-11demodulates QAM signal φ11to produce data pertaining to reverse channels R-111to R-11O; QAM demodulator922-1P demodulates QAM signal φ1Pto produce data pertaining to reverse channels R-1P1to R-1PO; QAM demodulator922-Q1demodulates QAM signal φQ1to produce data pertaining to reverse channels R-Q11to R-Q1O; and QAM demodulator922-QP demodulates QAM signal φQPto produce data pertaining to reverse channels R-QP1to R-QPO.

Thus, as exemplified, the transceiver900is capable of very broad bandwidth applications, allowing the reception of many data channels using three levels of channel demodulation: (1) wavelength division demodulation, (2) frequency division demodulation, and (3) quadrature amplitude/phase demodulation.

FIG. 10Aillustrates a block diagram of another exemplary transceiver1000with details on a transmitter portion thereof in accordance with another aspect of the disclosure. The transceiver1000may be employed in the subscribers' side of an optical communication system. The transceiver1000uses the same principles in transmitting reverse channel data to the head-end, as the head-end uses to transmit forward channel data to subscribers. That is, the transceiver1000uses three levels of channel modulation in the quadrature amplitude/phase domain, frequency division domain, and wavelength division domain to transmit reverse channel data to the head-end. Since transceiver900was discussed in detail above, and transceiver1000applies the same or similar principles, the following discussion on transceiver1000will be briefer.

InFIG. 10A, the details of the transmitter1010are shown, and the receiver1010is represented as a dashed block. The details of receiver are shown inFIG. 10B. The transmitter1010comprises a plurality of QAM modulators1012-1to1012-UT, a plurality of frequency modulators1014-11to1024-UT, a plurality of multiplexers1016-1to1016-U, and a plurality of optical transmitters1018-1to1018-U.

Data pertaining to reverse channels R-111-R-111S to R-1T1-R-1TS to R-U11-R-U1S to R-UT1-R-UTS are applied to QAM modulators1012-11to1012-1T to1012-U1to1012-UT to generate QAM signals φ11to φ1Tto φU1to φUT, respectively. The frequency modulators1014-11to1014-1T to1014-U1to1014-UT frequency modulate QAM signals φ11to φ1Tto φU1to φUTto generate frequency modulated carriers f11to f1Tto fU1to f1UT, respectively. The multiplexers1016-1to1016-U combines or multiplexes the frequency modulated carriers f11to f1Tto fU1to f1UTto generate FDM signals f11-f1Tto fU1-f1UT, respectively. The optical transmitters1018-1to1018-U modulate the FDM signals f11-f1Tto fU1-f1UTonto optical carriers to generate modulated optical carriers λR1to λRUrespectively. The WDM1050combines or multiplexes the modulated optical carriers λR1to λRUonto an optical communication medium (e.g., an optical fiber) to generate WDM signals λR1-λRUfor transmission to the head-end.

FIG. 10Billustrates a block diagram of the exemplary transceiver1000with details on a receiver portion thereof in accordance with another aspect of the disclosure. The transceiver1000uses the same principles in receiving forward channel data from the head-end, as the head-end uses to receive reverse channel data from subscribers. That is, the transceiver1000uses three levels of channel demodulation in the wavelength division domain, frequency division domain, and quadrature amplitude/phase domain to receive forward channel data from the head-end. Since transceiver900was discussed in detail above, and transceiver1000applies the same or similar principles, the following discussion on transceiver1000will be briefer.

InFIG. 10B, the details of the receiver1020are shown, and the transmitter1010, previously discussed in detail, is represented as a dashed block. In particular, the receiver1020comprises a plurality of optical receivers1028-1to1028-N, a plurality of de-multiplexers1026-1to1026-N, a plurality of frequency demodulators1024-11to1024-NM, and a plurality of QAM demodulators1022-11to1022-NM.

The WDM1050receives the WDM forward channel signals λF1-λFNand separates or de-multiplexes into separate modulated optical carriers λF1to λFN. The optical receivers1028-1to1028-N demodulate the optical carriers λF1to λFNto generate FDM signals f11-f1Mto fN1-fNM, respectively. The de-multiplexers1026-1to1026-N separates or de-multiplexes the FDM signals into separate modulated frequency carriers f11to f1Mto fN1to fNM, respectively. The frequency demodulators1024-1to1024-NM demodulates the modulated frequency carriers f11to f1Mto fN1to fNMto generate QAM signals φ11to φ1Mto φN1to φNM, respectively. The QAM demodulators1022-11to1022-1M to1022-N1to1022-NM perform quadrature demodulation of the QAM φ11to φ1Mto φN1to φNMto generate the data pertaining to forward channels F-111-F-11L to F-1M1-F-1ML to F-N11-FN1L, and to F-NM1-F-NML, respectively.

A difference between the transceiver900of the head-end and the transceiver1000is that generally the amount of forward channel data is substantially greater than the amount of reverse channel data. Accordingly, the head-end transceiver900may use QAM modulators of greater constellation points, such as QAM-64and QAM-256, whereas the subscriber-side transceiver1000may use QAM modulators of lesser constellation points, such as QAM-16. Along this line, the head-end transceiver900may use QAM demodulators of lesser constellation points, such as QAM-16, to receive the reverse channel data, whereas the subscriber unit transceiver1000may use QAM demodulators of greater constellation points, QAM-64and QAM-256, to receive the forward channel data.

Another difference between the transceiver900of the head-end and the subscriber-side transceiver1000is that the head-end transceiver900does not generally compete with another head-end in sending forward channel data to subscribers units, while subscriber units generally compete among each other in sending reverse channel data to the head-end. Accordingly, a channel assigning process may be implemented in each subscriber unit in order to prevent channel collision among the subscribers. For instance, a subscriber unit may have a dedicated or dynamically-assignable reverse channel including a distinct QAM constellation, a distinct frequency carrier and a distinct wavelength carrier. As another example, a particular wavelength channel may be assigned to subscriber units pertaining to a relatively wide geographical area (e.g., a city), a frequency channel pertaining to that particular wavelength channel may be assigned to subscriber units in a smaller geographical area (e.g., a particular neighborhood or section of the city), and the various phase channels pertaining to that particular frequency channel may be assigned to the individual subscriber units, respectively. However, it shall be understood that other arrangements pursuant to the teachings herein are possible.

Given this example of the subscriber unit transceiver, the following describes an example of how a return transmitter module (RTM) of a signal distribution hub may process the reverse channel data.

FIG. 11illustrates a block diagram of another exemplary return transmitter module (RTM)1100in accordance with another aspect of the disclosure. In this example, there are J optical transmission lines coupling respective taps to a signal distribution hub, as previously discussed herein. Also, in accordance with this example, each optical transmission line carries U wavelength channels. The RTM1100comprises distinct sets of optical receivers1102-11-1102-1J to1102-U1-1102-UJ, a plurality of combiners1104-1to1104-U, a plurality of optical transmitters1106-1to1106-U, and a wavelength division multiplexer (WDM)1108.

Each distinct set of optical receivers receive the same wavelength channel signal from the plurality of optical transmission lines coupling taps to the signal distribution hub by way of an optical distribution assembly (ODA), respectively. For instance, optical receivers1102-11to1102-1J receive the same wavelength channel signals λR1from the J optical transmission mediums by way of the ODA; optical receivers1102-21to1102-2J receive the same wavelength channel signals λR2from the J optical transmission mediums by way of the ODA; and optical receivers1102-U1to1102-UJ receive the same wavelength channel signals λRUfrom the J optical transmission mediums by way of the ODA.

Each wavelength from the separate optical transmission mediums may have been frequency modulated with distinct carrier frequency. Accordingly, the optical receivers demodulate the received optical signal to generate distinct modulated frequency carriers per each wavelength. For instance, optical receivers1102-11to1102-1J demodulate the same wavelength channel signals λR1from the separate optical transmission mediums to generate distinct modulated frequency carriers f11to f1T, respectively; optical receivers1102-21to1102-2J demodulate the same wavelength channel signals λR2from the separate optical transmission mediums to generate distinct modulated frequency carriers f21to f2T, respectively; and optical receivers1102-U1to1102-UJ demodulate the same wavelength channel signals λRUfrom the separate optical transmission mediums to generate distinct modulated frequency carriers fU1to fUT, respectively.

The combiners or multiplexers1104-1to1104-U combine the distinct modulated frequency carriers f11to f1Tto fU1to fUTto generate FDM signals f11-f1Tto fU1-fUT, respectively. The optical transmitters1106-1to1106-U modulate the FDM signals f11-f1Tto fU1-fUTonto distinct optical carriers to generate composite modulated optical carriers λRC1to λRCN, respectively. The WDM1108combines or multiplexes the modulated optical carriers λRC1to λRCNonto an optical communication medium to generate WDM signal λRC1-λRCNfor transmission to the head-end.