Power distribution devices, systems, and methods for radio-over-fiber (RoF) distributed communication

Power distribution devices, systems and methods for a Radio-over-Fiber (RoF) distributed communication system are disclosed. In one embodiment, an interconnect unit is coupled between a head-end unit and one or more remote units. The interconnect unit includes a plurality of optical communication links each configured to carry RoF signals to and from a head-end unit to remote units. The RF electrical signals from the head-end unit are converted to RF optical signals and communicated over the optical communication links in the interconnect unit to the remote units. The remote units convert the optical signals to electrical signals and communicate the electrical signals to client devices. To provide power to the remote units, the interconnect unit electrically couples power from at least one power supply to a plurality of power branches. Each power branch is configured to supply power to a remote unit connected to the interconnect unit.

TECHNICAL FIELD

The technology of the disclosure relates to providing power to remote units in a Radio-over-Fiber (RoF) distributed communication system.

BACKGROUND

Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, so-called “wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are being deployed in many different types of areas (e.g., coffee shops, airports, libraries, etc.). Wireless communication systems communicate with wireless devices called “clients,” which must reside within the wireless range or “cell coverage area” in order to communicate with an access point device.

One approach to deploying a wireless communication system involves the use of “picocells.” Picocells are radio-frequency (RF) coverage areas. Picocells can have a radius in the range from a few meters up to twenty meters as an example. Combining a number of access point devices creates an array of picocells that cover an area called a “picocellular coverage area.” Because the picocell covers a small area, there are typically only a few users (clients) per picocell. This reduces the amount of RF bandwidth shared among the wireless system users.

“Radio-over-Fiber” (RoF) wireless systems can be used to create picocells. A RoF wireless system utilizes RF signals conveyed over optical fibers. Such systems include a head-end station optically coupled to a plurality of remote units. The remote units each include transponders that are coupled to the head-end station via an optical fiber link. The transponders in the remote units are transparent to the RF signals. The remote units simply convert incoming optical signals from the optical fiber link to electrical signals via optical-to-electrical (O/E) converters, which are then passed to the transponders. The transponders convert the electrical signals to electromagnetic signals via antennas coupled to the transponders in the remote units. The antennas also receive electromagnetic signals from clients in the cell coverage area and convert the electromagnetic signals to electrical signals. The remote units then convert the electrical signals to optical signals via electrical-to-optical (E/O) converters. The optical signals are then sent to the head-end station via the optical fiber link. Because the remote units include power consuming components, including O/E and E/O converters, electrical power must be provided to the remote units.

SUMMARY

Embodiments disclosed in the detailed description include power distribution devices, systems, and methods for Radio-over-Fiber (RoF) distributed communications. In one embodiment, an interconnect unit is coupled between a head-end unit and one or more remote units. The interconnect unit includes a plurality of optical communication links each configured to carry RoF signals between a head-end unit and a remote unit. To provide power to the remote units, the interconnect unit electrically couples power from at least one power supply to a plurality of power branches in the interconnect unit. Each power branch is configured to supply power to a remote unit when connected to the interconnect unit. In this manner, power is not required to be run from the heat-end unit to the remote units. Further, power supplies are not required in the remote units, would require additional space and also require each remote unit to be located in proximity to a power source, thus decreasing flexibility in placement in a building or other area.

In one embodiment, the electrical signals from the head-end unit are converted to optical signals and communicated over the optical communication links to the remote units via optical connections established in the interconnect unit. The remote units convert the optical signals to electrical signals and radiate the electrical signals via an antenna to client devices in the range of the antenna to provide a picocell. Each picocell from the remote units can be combined to form a picocell coverage area or areas for client device communications.

In another embodiment, the interconnect unit includes a bulk power supply that is configured to supply power to all remote units connected to the interconnect unit. In another embodiment, a plurality of power supplies are provided wherein power is partitioned from each power supply to a subset of remote units connected to the interconnect unit.

In another embodiment, a power distribution module is also provided in the interconnect unit to facilitate distribution of power to remote units connected to the interconnect unit. The power distribution module can be electrically coupled between a power supply and a plurality of power branches and configured to distribute power to a plurality of remote units. The power distribution module can provide one or more protection circuits to protect the interconnect unit and the remote units from damage caused by power irregularities or related power conditions, including power surges and electrostatic discharge (ESD) events as examples. In one embodiment, the power distribution module includes a voltage protection circuit. The voltage protection circuit may include an over-voltage protection circuit and/or a reverse-voltage protection circuit. In another embodiment, the power distribution module can include a current protection circuit. The current protection circuit can include an over-current protection circuit. An under-voltage sensing circuit and power level indicators may also be provided to indicate when the power level is not sufficient to properly operate the remote units.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all embodiments are shown. Indeed, the concepts may be embodied in many different forms and should not be construed as limiting herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Embodiments disclosed in the detailed description include power distribution devices, systems, and methods for Radio-over-Fiber (RoF) distributed communications. In one embodiment, an interconnect unit is coupled between a head-end unit and one or more remote units. The interconnect unit includes a plurality of optical communication links each configured to carry RoF signals between a head-end unit and a remote unit. To provide power to the remote units, the interconnect unit electrically couples power from one or more power supplies to a plurality of power branches in the interconnect unit. Each power branch is configured to supply power to a remote unit when connected to the interconnect unit. In this manner, power is not required to be run from the head-end unit to the remote units. Further, power supplies are not required in the remote units, would require additional space and also require each remote unit to be located in proximity to a power source, thus decreasing flexibility in placement in a building or other area.

Although the embodiments of power distribution from interconnect units (ICUs) to remote units described herein can be used and employed in any type of RoF distributed communication system, an exemplary RoF distributed communication system10is provided inFIG. 1to facilitate discussion of power distribution.FIG. 1includes a partially schematic cut-away diagram of a building infrastructure12that generally represents any type of building in which the RoF distributed communication system10might be employed and used. The building infrastructure12includes a first (ground) floor14, a second floor16, and a third floor13. The floors14,16,18are serviced by a head-end station or head-end unit (HEU)20, through a main distribution frame22, to provide a coverage area24in the building infrastructure12. Only the ceilings of the floors14,16,18are shown inFIG. 1for simplicity of illustration.

In an example embodiment, the HEU20is located within the building infrastructure12, while in another example embodiment the HEU20may be located outside of the building infrastructure12at a remote location. A base transceiver station (BTS)25, which may be provided by a second party such as a cellular service provider, is connected to the HEU20, and can be co-located or located remotely from the HEU20. In a typical cellular system, for example, a plurality of base transceiver stations are deployed at a plurality of remote locations to provide wireless telephone coverage. Each BTS serves a corresponding cell and when a mobile station enters the cell, the BTS communicates with the mobile station. Each BTS can include at least one radio transceiver for enabling communication with one or more subscriber units operating within the associated cell.

A main cable26is optically coupled to or includes multiple fiber optic cables32distributed throughout the building infrastructure12, which are coupled to remote units28that provide the coverage area24for the first, second and third floors14,16, and18. The remote units28may also be referred to as “remote antenna units.” Each remote unit28in turn services its own coverage area in the coverage area24. The main cable26can include a riser cable30that carries all of the uplink and downlink fiber optic cables32to and from the HEU20. The main cable26can also include one or more multi-cable (MC) connectors adapted to connect select downlink and uplink optical fiber cables to a number of fiber optic cables32. In this embodiment, an interconnect unit (ICU)34is provided for each floor14,16,18, the ICUs34including a passive fiber interconnection of optical fiber cable ports which will be described in greater detail below. The fiber optic cables32can include matching connectors. In an example embodiment, the riser cable30includes a total of thirty-six (36) downlink and thirty-six (36) uplink optical fibers, while each of the six (6) fiber optic cables32carries six (6) downlink and six (6) uplink optical fibers to service six (6) remote units28. Each fiber optic cable32is in turn connected to a plurality of remote units28each having an antenna that services a portion of the overall coverage area24.

In this example embodiment, the HEUs20provide electrical radio-frequency (RF) service signals by passing (or conditioning and then passing) such signals from one or more outside networks21to the coverage area24. The HEUs20are electrically coupled to an electrical-to-optical (E/O) converter36within the HEU20that receives electrical RF service signals from the one or more outside networks21and converts them to corresponding optical signals. The optical signals are transported over the riser cables30to the ICUs34. The ICUs34may include passive fiber interconnection of optical fiber cable ports that pass the optical signals over the fiber optic cables32to the remote units28to provide the coverage area24. In an example embodiment, the E/O converter36includes a laser suitable for delivering sufficient dynamic range for the RoF applications, and optionally includes a laser driver/amplifier electrically coupled to the laser. Examples of suitable lasers for the E/O converter36include laser diodes, distributed feedback (DFB) lasers, Fabry-Perot (FP) lasers, and vertical cavity surface emitting lasers (VCSELs).

The HEUs20are adapted to perform or to facilitate any one of a number of RoF applications, including but not limited to radio-frequency identification (RFID), wireless local area network (WLAN) communication, and/or cellular phone service. In a particular example embodiment, this includes providing WLAN signal distribution as specified in the IEEE 802.11 standard, i.e., in the frequency range from 2.4 to 2.5 GHz and from 5.0 to 6.0 GHz. In another example embodiment, the HEUs20provide electrical RF service signals by generating the signals directly. In yet another example embodiment, the HEUs20coordinate the delivery of the electrical RF service signals between client devices within the coverage area24.

The number of optical fibers and fiber optic cables32can be varied to accommodate different applications, including the addition of second, third, or more HEUs20. In this example, the RoF distributed communication system10incorporates multiple HEUs20to provide various types of wireless service to the coverage area24. The HEUs20can be configured in a master/slave arrangement where one HEU20is the master and the other HEU20is a slave. Also, one or more than two HEUs20may be provided depending on desired configurations and the number of coverage area24cells desired.

FIG. 2is a schematic diagram of an example embodiment of the HEU20connected to one of the remote units28to facilitate further discussion of operational aspects of the RoF distributed communication system10ofFIG. 1The remote unit28creates a picocell39that together with other picocells39formed from other remote units28, as illustrated inFIG. 1, provide the coverage area24. The HEU20includes a service unit40that provides electrical RF service signals for a particular wireless service or application. In an example embodiment, the service unit40provides electrical RF service signals by passing (or conditioning and then passing) such signals from the one or more outside networks21. The service unit40is electrically coupled to an electrical-to-optical (E/O) converter42that receives an electrical RF service signal from the service unit40and converts it to a corresponding optical signal. The HEU20also includes an optical-to-electrical (O/E) converter44electrically coupled to the service unit40. The O/E converter44receives an optical RF service signal and converts it to a corresponding electrical signal. In an example embodiment, the O/E converter44is a photodetector, or a photodetector electrically coupled to a linear amplifier. The E/O converter42and the O/E converter44constitute a “converter pair”46.

In an example embodiment, the service unit40includes an RF signal modulator/demodulator unit48that generates an RF carrier of a given frequency and then modulates RF signals onto the carrier. The RF signal modulator/demodulator unit48also demodulates received RF signals. The service unit40also includes a digital signal processing unit (“digital signal processor”)50, a central processing unit (CPU)52for processing data and otherwise performing logic and computing operations, and a memory unit54for storing data, such as system settings and status information, RFID tag information, etc. In an example embodiment, the different frequencies associated with the different signal channels are created by the RF signal modulator/demodulator unit48generating different RF carrier frequencies based on instructions from the CPU52. Also, as described below, the common frequencies associated with a particular combined picocell are created by the RF signal modulator/demodulator unit48generating the same RF carrier frequency.

With continuing reference toFIG. 2, in an example embodiment, the fiber optic cable32from the converter pair46in the HEU20is connected to the ICU34. The ICU34provides a passive connection of the optical signals from the HEU20to the remote unit28, as will be described below. The remote unit28also includes a converter pair46, wherein the E/O converter42and the O/E converter44therein are electrically coupled to an antenna system56via an RF signal-directing element58, such as a circulator. Because the converter pair46in the remote unit28requires power to operate, a power distribution module59is also provided in the ICU34to distribute power to the remote unit28and any other remote units28connected to the ICU34. Power is required to power the converter pair46and/or other power-consuming components in the remote unit28. According to one aspect of the present embodiment, providing power to the remote units28from the ICU34prevents the need for each remote unit28to provide a power supply thus saving cost and reducing the size of the remote units28. Further, the remote unit28may not be in sufficient proximity to a power source to be placed such that the picocell39is in the desired area. Providing power from the HEU20would require providing power either in separate cables or within the riser cables30, which would require the HEU20to provide sufficient power for all possible remote units28adding complexity and cost.

In this embodiment, a DC power converter60is electrically coupled to the converter pair46in the remote unit28, and changes the voltage or levels of an electrical power signal generated by a power supply100(FIG. 3) and provided over electrical power lines61to the power level(s) required by the power-consuming components in the remote unit28. In an example embodiment, the DC power converter60is either a DC/DC power converter, or an AC/DC power converter, depending on the type of electrical power signal carried by the electrical power line61. In an example embodiment, the electrical power line61includes standard electrical-power-carrying electrical wire(s), e.g., 18-26 AWG (American Wire Gauge) used in standard telecommunications and other applications. More detail regarding an exemplary power distribution module59that can be provided in the ICU34is described in more detail below starting withFIG. 3.

Turning back toFIG. 2, the RF signal-directing element58serves to direct the downlink and uplink electrical RF service signals. In an example embodiment, the antenna system56includes one or more patch antennas, such as disclosed in U.S. Patent Application Publication No. 2008/0044186, published on Feb. 21, 2008, which patent application is incorporated herein by reference. The remote unit28in this embodiment has few signal-conditioning elements and no digital information processing capability. Rather, the information processing capability is located remotely in the HEU20, and in a particular example, in the service unit40. This allows the remote unit28to be very compact and virtually maintenance-free. In addition, the preferred example embodiment of the remote unit28consumes very little power, is transparent to RF signals, and does not require a local power source, as will be described in more detail below.

With reference again toFIG. 2, the fiber optic cable32includes a downlink optical fiber62D having an input end63and an output end64, and an uplink optical fiber62U having an input end66and an output end68. The downlink and uplink optical fibers62D and62U optically couple the converter pair46in the HEU20to the converter pair46in the remote unit28. Specifically, the downlink optical fiber input end63is optically coupled to the E/O converter42of the HEU20, while the output end64is optically coupled to the O/E converter44of the remote unit28. Similarly, the uplink optical fiber input end66is optically coupled to E/O converter42of the remote unit28, while the output end68is optically coupled to the O/E converter44of the HEU20. In an example embodiment, the RoF distributed communication system10employs a known telecommunications wavelength, such as 850 nm, 1300 nm, or 1550 nm as examples. In another example embodiment, the RoF distributed communication system10employs other less common but suitable wavelengths, such as 980 nm as an example.

With reference to the RoF distributed communication system10ofFIG. 1andFIG. 2, the service unit40generates an electrical downlink RF service signal SD (“electrical signal SD”) corresponding to its particular application. In an example embodiment, this is accomplished by the digital signal processor50providing the RF signal modulator/demodulator unit48with an electrical signal (not shown) that is modulated onto an RF carrier to generate a desired electrical signal SD. The electrical signal SD is received by the E/O converter42in the HEU20, which converts this electrical signal SD into a corresponding optical downlink RF signal SD′ (“optical signal SD′”), which is then coupled into the downlink optical fiber62D at the input end63. The optical signal SD′ is tailored to have a given modulation index. The modulation power of the E/O converter42is controlled (e.g., by one or more gain-control amplifiers, not shown) to vary the transmission power from the antenna system56. In an example embodiment, the amount of power provided to the antenna system56is varied to define the size of the associated picocell39.

The optical signal SD′ travels over the downlink optical fiber62D to the output end64, where it is received by the O/E converter44in the remote unit28. The O/E converter44converts the optical signal SD′ back into electrical signal SD, which then travels to the RF signal-directing element58. The RF signal-directing element58then directs the electrical signal SD to the antenna system56. The electrical signal SD is fed to the antenna system56, causing it to radiate a corresponding electromagnetic downlink RF signal SD″ (“electromagnetic signal SD″”) according to the radiation pattern of the antenna system56to provide the picocell39. A client device70, and more particular a client device antenna72associated with the client device70, can receive the electromagnetic signal SD″ when present in the picocell39. The client device antenna72may be part of a wireless card or a cell phone antenna, as examples. The client device antenna72converts the electromagnetic signal SD″ into an electrical signal SD in the client device70(signal SD is not shown therein).

The client device70can generate electrical uplink RF signals SU (not shown in the client device70), which are converted into electromagnetic uplink RF signals SU″ (“electromagnetic signal SU″”) by the client device antenna72. The electrical signal SU is directed by the RF signal-directing element58to the E/O converter42in the remote unit28, which converts this electrical signal SU into a corresponding optical uplink RF signal SU′ (“optical signal SU′”), which is then coupled into the input end66of the uplink optical fiber62U. The optical signal SU′ travels over the uplink optical fiber62U to the output end68, where it is received by the O/E converter44in the HEU20. The O/E converter44converts the optical signal SU′ back into electrical signal SU, which is then directed to the service unit40. The service unit40receives and processes the electrical signal SU, which in an example embodiment includes one or more of the following: storing the signal information; digitally processing or conditioning the signals; sending the signals to one or more outside networks21via network links74; and sending the signals to one or more client devices70in the coverage area24. In an example embodiment, the processing of electrical signal SU includes demodulating this electrical signal in the RF signal modulator/demodulator unit48, and then processing the demodulated signal in the digital signal processor50.

FIG. 3is a schematic diagram illustrating more detail regarding the exemplary ICU34in the RoF distributed communication system10ofFIGS. 1 and 2. To provide the optical connections between optical fibers in the riser cable30and the remote units28, a furcation80from the riser cable30connected to the HEU20is brought to the ICU34. The furcation80breaks pairs of optical fibers82from the riser cable30into optical communication input links. The optical communication input links in this embodiment are downlink and uplink optical fibers62D,62U configured to be connected to the remote units28. The downlink optical fiber62D carries RoF signals from the HEU20to the remote units28, and the uplink optical fiber62U carries RoF signals from the remote units28to the HEU20. The furcation80contains at least two optical fibers82in one or more furcated legs84to provide at least one downlink and uplink optical fiber62D,62U pair to allow the ICU34to service one remote unit28. However, more than one pair of optical fibers82may be provided by the furcation80to allow the ICU34to service more than one remote unit28. A pair of downlink and uplink optical fibers62D,62U is provided for each remote unit28serviced by the ICU34. Each of the downlink and uplink optical fibers62D,62U may be provided in one furcation80as illustrated inFIG. 3, or in multiple furcations brought to the ICU34.

To complete the connection of the downlink and uplink optical fibers62D,62U to the remote units28, the furcated legs84are connected to optical fibers in furcated legs86. The furcated legs86are provided from furcations88of fiber optic cables90from the remote units28to provide optical communication output links. In this embodiment, the ICU34is configured to service up to six (6) remote units28. The furcated legs84may be pre-connectorized with a fiber optic connector92to facilitate easy connections within the ICU34. The fiber optic connectors92can be connected to fiber optic adapters94which receive fiber optic connectors96from preconnectorized furcated legs86to complete the optical connection between the downlink and uplink optical fibers in the remote units28to the optical fibers82in the riser cable30from the HEU20. Other methods of connecting the optical fibers82to the remote units28, including but not limited to splicing and the providing of splices and/or splice trays in the ICU34, are also possible.

As previously stated, the remote units28contain power-consuming components that must be powered for the remote unit28to properly operate. In this regard in this exemplary embodiment, the fiber optic cables90contain electrical conductors, namely two conductors for power and ground in this example, that allow power to be distributed through the fiber optic cables90to multiple remote units28. The fiber optic cables90may be hybrid cables that contain both optical fibers and electrical conductors as shownFIG. 3, or the electrical conductors could be run through separate wiring or cabling to the remote units28if desired. In this exemplary embodiment, the furcations88provide electrical furcated legs98that are configured to receive power. The electrical furcated legs98are electrically coupled to a power distribution module59which receives power from a power supply100to provide power to the remote units28. By providing the power supply100and the power distribution module59in the ICU34, power sources do not have to be provided in the remote units28, nor do the remote units28have to be located within reach of power sources. Further, the HEU20does not have to provide power supplies and associated electrical cabling to power the remote units28. The power supply100associated with the ICU34can distribute power to multiple remote units28.

In this embodiment, the power supply100is located within the ICU34, but could also be located outside of the ICU34. The power supply100may also be an uninterruptable power supply. The power supply100, which may be also referred to as a bulk power supply100, provides DC power to the remote units28in this embodiment. The power supply100receives either AC or DC power into a power input102. The power input102may receive 110V to 240V AC or DC power from a power line104connected to a power source106as an example. In one embodiment, a transformer (not shown) converts AC power from the power input102to DC power on a power output108. For example, the AC/DC transformer could transform 110V-240V alternating current (AC) power that is readily available in the building infrastructure12into DC power for distribution by the power distribution module59to the remote units28. An another example, a DC/DC converter could be provided in the power supply100to convert DC power on the power input102to DC power on the power output108. The power from the power supply100is split to each of the remote units28as will be described in more detail below.

The power supply100can be provided to produce any voltage level of DC power desired. In one embodiment, the power supply100can produce relatively low voltage DC current to the electrical power lines61. Likewise, the power distribution module59can support distributing the low voltage DC power provided by the power supply100to the electrical conductors in the electrical power lines61for powering the remote units28. In this example, the power output108is a low voltage of approximately forty-eight (48) volts DC or less, and may be in the range of twenty-four to forty-eight (48) Volts DC. A low voltage may be desired so that the ICU34is power-limited and Safety Extra Low Voltage (SELV) compliant, although such is not required. For example, according to Underwriters Laboratories (UL) Publication No. 69060, SELV-compliant circuits produce voltages that are safe to touch both under normal operating conditions and after faults. The voltage between any two conductors and between any one conductor and ground (i.e., earth) should not exceed 60V DC and 42.4 Volts peak under normal operating conditions. The total power for a SELV compliant power supply is limited to approximately 100 VA. Article 725 of the National Electric Code (NEC) provides for power-limited circuits. The 100 VA limit discussed therein is for a Class 2 DC power source, as shown in Table 11(B) in Article 725. Providing a SELV compliant power supply100and ICU34may be desired or necessary for fire protection and to meet fire protection and other safety regulations and/or standards. Further, since operations may frequently interact with the ICU34and the connections provided therein during installation and configurations of the ICU34and the optical connections provided therein between the optical fibers in the riser cable30and the remote units28, providing a power supply100that produces a SELV may be desired to avoid accidental shocks or electrocutions.

It may further be desired to provide additional power management features in the power distribution module59before the power from the power supply100is transferred from the ICU34to the remote units28. For example, as illustrated inFIG. 3, the power distribution module59can include one or more voltage protection circuits110. For example, an over-voltage protection circuit112may be provided in the power distribution module59that is coupled to input power lines113from the power supply100to prevent power surges from damaging equipment or circuits within the ICU34and at the remote units28. The over-voltage protection circuit112redirects power from the power supply100away from power branches115in the power distribution module59if an over-voltage condition is detected. By example only, the over-voltage protection circuit112may be designed to redirect power if the voltage level is greater than five to fifty percent (5-50%) above the nominal voltage level for the power supply100. Providing over-voltage protection also protects against surges due to electrostatic discharge (ESD) events which may occur due to discharges by the power supply100, such as due to malfunctions, electrostatic energy present in areas surrounding the power supply100and/or the ICU34, and/or from technician intervention, such as if a technician is not properly grounded when servicing the ICU34.

In this embodiment, as illustrated inFIG. 3, the over-voltage protection module112is located in the power distribution module59in a common branch114prior to the power being split and distributed among power branches115that are electrically coupled to the remote unit28. The voltage level is split to each of the power branches115in parallel, so voltage levels in each of the power branches115is the same or essentially the same. Thus, it is not necessary to protect each individual power branch115from an over-voltage condition. An over-voltage condition, if present, would be present in each of the power branches115without distinction. However, the over-voltage protection circuit112could be provided in each power branch115if desired, but such would likely incur additional costs. More discussion regarding an exemplary embodiment of the over-voltage protection circuit112is described below with regard toFIG. 4.

It may also further be desired to provide reverse-voltage protection in the power distribution module59to protect against a reverse-voltage condition. Reverse-voltage protection prevents a reverse polarity (i.e., a negative voltage) in voltage from being supplied by the power supply100, which could otherwise damage components in the power distribution module59and at the remote units28. For example, a technician may accidentally reverse power and ground lines or leads in the input power lines113leading from the power supply100to the power distribution module59. Certain components in the power distribution module59and/or the remote unit28may be damaged if a reverse-voltage is applied to certain of their components. In this regard, a reverse-voltage protection circuit116may be provided in the power distribution module59that is coupled to the input power lines113from the power supply100. The reverse-voltage protection circuit116redirects power from the power supply100away from the power branches115if a reverse voltage condition is detected. For example, the reverse-voltage protection circuit116may redirect power if the voltage level produced by the power supply100reaches 0.3 to 5.0 V.

In this embodiment, as illustrated inFIG. 3, the reverse-voltage protection module116is located in the power distribution module59in the common branch114prior to the power being split and distributed among power branches115that are electrically coupled to the remote unit28. A reverse-voltage condition, if present, would be present in each of the power branches115without distinction. However, the reverse-voltage protection circuit116could be provided in each power branch115if desired. More discussion regarding an exemplary embodiment of the reverse-voltage protection circuit116is described below with regard toFIG. 4.

Within each power branch115, current protection and other power detection and related circuits may be provided. In the embodiment inFIG. 3, the power supply100is power enough to supply power to all remote units28connected to the ICU34. Thus, the power supply100is powerful enough to produce an over-current condition in a power branch115if a power splitting malfunction occurs. In this regard and in this embodiment as illustrated inFIG. 3, over-current protection circuits118may be provided in each power branch115. In this embodiment, the ICU34is configured to support up to six (6) remote units28, and thus six (6) over-current protection circuits118are provided, although such is not required or limiting. The over-current protection circuits118are electrically coupled to split power outputs120from the voltage protection circuit(s)110in this embodiment. The over-current protection circuits118protect the components in the ICU34and the remote units28from being damaged due to an over-current condition generated by the power supply100or other cause, such as an unintended short circuit in the power distribution module59for example.

Unlike the voltage protection circuits110, the over-current protection circuits118are included in the individual power branches115since current level can differ among the power branches115. By placing the over-current protection circuits118in each power branch114, over-current conditions present in a particular power branch115can be isolated. However, the over-current protection circuit118could be placed in a common branch114if desired. As an example, the over-current protection circuits118may be designed to detect if the current level is at least approximately five to two hundred percent (5-200%) above nominal current levels in a power branch115. More discussion regarding an exemplary embodiment of the over-current protection circuits118is described below with regard toFIGS. 4 and 5.

It may also be desired to provide an under-voltage sensing circuit122in the power distribution module59. An under-voltage level (but not meaning reverse voltage) typically will not damage components in the ICU34and the remote units28. However, under-voltage conditions can cause the ICU34and/or the remote units28to not properly operate. Some circuits and components, including those that may be provided in the power branches115of the ICU34and in the remote units28, require a minimum operation voltage to properly operate. If the voltage level produced by the power supply100is insufficient, a remote unit28may not properly operate and may go offline, meaning that the remote unit28may not send and receive RF signals to a client device70(seeFIG. 2). Thus, sensing under-voltage conditions can assist in troubleshooting the ICU34and the power supply100and/or power distribution module59.

The under-voltage sensing circuits122are electrically coupled to outputs123of the under-current protection circuits118in this embodiment, as illustrated inFIG. 3. The under-voltage sensing circuits122are located on the remote unit28side of the power distribution module59so that any over-voltage, reverse-voltage, and/or over-current protections are provided before the power reaches the under-voltage sensing circuits122in this embodiment. The under-voltage sensing circuits122require power from the power supply100to operate in this embodiment. Further, it may be desired to detect the power levels in each of the power branches115individually. Thus, since the ICU34is configured to support up to six (6) remote units28in this embodiment, six (6) under-voltage power sensing circuits122are provided, although such is not required or limiting.

If a remote unit28is not properly operating, a technician may be dispatched to diagnose the problem. If the problem is a result of an insufficient or under-voltage provided by the power supply100, the under-voltage sensing circuit122can indicate to the technician that an insufficient voltage level is being produced by the power supply100. The power distribution module59may include power level indicators124that are electrically coupled to each under-voltage sensing circuit122to provide an indication of the power level in the power distribution module59to a technician or other device. As an example, the power level indicators124may have a visual indicator, such as one or more light emitting diodes (LEDs) as an example, indicative of the voltage level or an under-voltage condition in the ICU34. If the power level is insufficient as a result of any power level condition, including an under-voltage condition, corrective measures can be taken, such as diagnosing the power connections in the ICU34as an example, and replacing the power supply100, if needed. More discussion regarding an exemplary embodiment of the under-voltage sensing circuits122is described below with regard toFIGS. 4 and 5.

Unless the over-voltage protection circuit112, the reverse-voltage protection circuit116, and/or the over-current protection circuits118redirect power, the power distribution module59transfers the received power from the power supply100to the power output lines126. To couple the power to the remote units28in this embodiment, the power output lines126are electrically coupled to the electrical furcated legs98, which are run to each of the remote units28. The power output lines126may be separate power lines that are electrically connected to the electrical furcated legs98, or the electrical furcated legs98for each of the remote units28may be directly connected to over-voltage protection circuits112.

FIG. 4illustrates a schematic diagram of the power distribution module59inFIG. 3illustrating more details regarding the circuit and the components contained therein for this embodiment. As illustrated inFIG. 4, the input power lines113come from the power supply100into the power distribution module59. The positive input power line113is coupled to a VS1node130and a ground (GND) node132. The voltage protection circuit110is provided in this embodiment by the VS1node130being coupled to a cathode k of a diode134configured in a reverse bias mode. The anode ‘a’ of the diode134is coupled to the GND node132. A fuse136is also coupled to the cathode ‘k’ of the diode134in this embodiment. During normal voltage levels, the diode134is an open circuit. Current flows through the fuse136and the voltage level is applied in parallel on each of the power outputs120to each of the power branches115as illustrated inFIG. 3.

When the voltage level supplied from the power supply100at the VS1node130rises above an excess voltage level approximately equal to the activation voltage drop level in order to activate or “turn-on” the diode134, the diode134will become a short circuit to shunt excess current to the GND node132. This directs power from the power supply100away from the remainder of the components in the power branches115of the power distribution module59(as illustrated inFIG. 3) and protects the remote units28from an over-voltage condition. Also, the fuse136becomes an open circuit in response to the over-current draw from the power supply100as a result of the short circuit operation of the diode134to provide a current limiting function to protect the diode134. Further, because the diode134is provided in a reverse bias mode, the diode134will also short to the GND node124when a negative voltage is applied across the VS1and GND nodes130,132. Thus, in this example, the over-voltage protection circuit112and the reverse-voltage protection circuit116are provided as part of the same circuit, although such is not required.

In this embodiment, the diode134is a transient voltage suppression (TVS) diode. A TVS diode can be used to protect sensitive electronics from voltage spikes. A TVS diode is similar to a Zener diode in that it permits current in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than a breakdown voltage. Thus, a TVS diode can be used to protect for both over-voltage and reverse-voltage conditions. However, any type of over-voltage protection device may be employed. In this embodiment, the fuse136is a power temperature coefficient (PTC) fuse which is resettable to provide a short circuit for normal operation when the current drawn from the power supply100lowers beyond the current limiting threshold of the PTC fuse. However, any type of over-current protection device may be employed. A resettable fuse may be desirable to prevent the fuse from having to be manually replaced.

Further, in this embodiment, a second diode134′ and resettable fuse136′ are provided in parallel and coupled to the VS1node130and the GND node132. The second diode134′ and resettable fuse136′ partition the over-voltage and reverse-voltage protection between the two diodes134,134′ and the current limiting over the two fuses136,136′ to narrow the required current voltage and current limiting range of the diodes134,134′ and the fuses136,136′, respectively. However, only one partition or more than two partitions may be provided as desired.

The power distribution module59in this embodiment also includes a DC-to-DC converter140to provide a second voltage at VS2node142from the voltage provided by the power supply100at the VS1node130. In this example, the voltage level provided by the power supply100at the VS1node130is approximately 48V. The DC-to-DC converter140is configured to transform this 48V to approximately 5V at the VS2node142. This is so a lower voltage can be used to provide power to the under-voltage sensing circuits122and power level indicators124in the power distribution module59that require approximately 5V in this example.

FIG. 5illustrates an over-current protection circuit118and under-voltage sensing circuit122in one power branch115of the power distribution module59ofFIG. 3. It is understood that the illustrated over-current protection circuit118and under-voltage sensing circuit122inFIG. 5may be provided in each of the power branches115in the power distribution module59, but for simplicity of illustration and discussion purposes, only one over-current protection circuit118and under-voltage sensing circuit122for one power branch115is illustrated inFIG. 5. The discussion here is equally applicable for all other power branches115of the power distribution module59.

As illustrated inFIG. 5, the over-current protection circuit118is provided in the form of a fuse144in this embodiment. The fuse144provides an open circuit if the current exceeds a designed current level according to the type and characteristics of the fuse144. In this embodiment, the fuse144is a PTC resettable fuse. The fuse144resets when the current level lowers beyond the over-current condition. During normal current conditions or once the fuse144resets after an over-current condition, the current flows to an output node146of the fuse144, which is coupled to the power output lines126electrically coupled to the remote units28to provide power to the remote units28. To output node146of the fuse144is also coupled in parallel to the under-voltage sensing circuit122and power level indicator124in this embodiment, as illustrated inFIG. 5. The under-voltage sensing circuit122monitors the voltage level and does not redirect power.

The output node146is coupled to a resistor divider network148to provide a ratio of the voltage level to a node150that is input into an input voltage pin (VIN) in a voltage comparator152. In this embodiment, the voltage comparator152is an integrated circuit (IC) provided in an IC chip. For example, the voltage comparator152may be the MC33064 under-voltage sensing integrated circuit IC. The reference voltage is set in an internal circuit in the voltage comparator152in this embodiment. However, any type of voltage comparator152may be provided. If the voltage level on the node150drops below a reference voltage level setting in the voltage comparator150, the voltage comparator152pulls a reset line154to a low or zero voltage. The reset line154is coupled to an input156of a switch158, which may be a transistor, including but not limited to a field effect transistor (FET), or any other type of transistor. A pull-up resistor160is coupled between the VS2node142and the reset line154to provide a bias voltage to the switch158. If the switch158is activated by the reset line154being pulled low, the switch158activates or turns on to provide a current flow path between the VS2node142and the GND node132. Current flows through an LED161to emit light to indicate the under-voltage condition to a technician. A current-limiting resistor162protects the LED161from an over-current condition.

Depending on the environmental conditions, the power supply100associated with the ICU34may behave differently at reduced conditions. For example, at higher temperatures, the output wattage of the power supply100described above and illustrated inFIG. 3can be reduced from approximately 180 W (e.g., at room temperature) to 140 W (i.e., at higher temperatures) under maximum loads. This reduction in power may not be sufficient to properly power the remote units28depending on the number of remote units28connected to the ICU34. For example, in the ICU34example inFIG. 3, the remote units28may require approximately 36-40 W of power for a total of between 144 W-150 W. However, at elevated temperatures, the power supply100may be unable to provide this power to each power branch115in the power distribution module59. Selecting a power supply100with a higher power rating to compensate for reduction in power due to reduced conditions may not be possible in order to comply with low voltage requirements previously described. Additional cooling devices, such as fans or heat sinks, may also be required, adding cost to the ICU34.

In this regard,FIG. 6illustrates an alternate embodiment of the ICU34that may be employed to provide sufficient power to the remote units28under reduced conditions. In this embodiment, more than one power supply100is provided. Power from each power supply100can be partitioned to only provide power to a subset of the remote units28. Each power supply100provides power to its own dedicated power distribution module59which in turn services a subset of the maximum remote units28that can be connected to the ICU34. Providing multiple power supplies100also reduce the power output requirements of each power supply100over the requirements should a single power supply100be employed like provided in the exemplary ICU34ofFIG. 3. Note that providing more than one power supply100is not required. For example, the maximum number of remote units28could be reduced to compensate for reduced conditions of the power supply100as an alternative. Further, the power requirements of the remote units28could be reduced to lower the overall power requirements on the power supply100as another alternative.

FIG. 7illustrates an exemplary ICU34that may be employed in the exemplary Radio-over-Fiber (RoF) distributed communication system10ofFIGS. 1 and 2and may be configured according to any of the embodiments described above. As illustrated inFIG. 7, the ICU34may be provided in an enclosure170. The enclosure170may have side doors172,174that are configured to hold the furcations88,80, respectively from the fiber optic cable90to the remote unit28and the riser cable30, respectively (see also,FIG. 3). The furcation80of the riser cable30breaks pairs of optical fibers from the riser cable30to provide optical communication input links. The optical communication input links in this embodiment are the downlink and uplink optical fibers62D,62U (FIG. 3) to be connected to the remote units28. In this embodiment, the furcated leg86contain twelve (12) optical fibers to provide connections up to six (6) remote units28although only one remote unit28is illustrated as connected inFIG. 7.

To complete the passive connection of the downlink and uplink optical fibers62D,62U to the remote units28, the furcated legs84are connected to furcated legs86provided in furcations88of fiber optic cables90from the remote units28. The furcated legs84are pre-connectorized with the fiber optic connector92to facilitate easy connections within the ICU34. The fiber optic connectors92can be connected to the fiber optic adapters94which receive the fiber optic connectors96from pre-connectorized furcated legs86to complete the optical connection between the downlink and uplink optical fibers62D,62U in the remote units28to the optical fibers82in the riser cable30from the HEU20.

The furcations88also provide the electrical furcated legs98that are configured to receive power from the power supply100. The electrical furcated legs98are electrically coupled to a power terminal176contained inside the enclosure of the ICU34in this embodiment. The electrical furcated legs98may be pre-connectorized with an electrical connector178that is configured to connect to an electrical connector180in the power terminal176. A connection (not shown) is made between the power terminal176and the power distribution module59which receives power from a power supply100to provide power to the remote units28. The power distribution module59is not shown inFIG. 7. The power distribution module59may be disposed in the enclosure170or anywhere else desired on the ICU34including but not limited to within a rear wall182of the enclosure170or on the backside of the rear wall182as examples. Further in this embodiment, two power terminals176are provided to support all necessary power connections and in the event that more than one power supply100is provided to partition power as illustrated and discussed by example inFIG. 6.

The ICU discussed herein can encompass any type of fiber optic equipment and any type of optical connections and receive any number of fiber optic cables or single or multi-fiber cables or connections. The ICU may include fiber optic components such as adapters or connectors to facilitate optical connections. These components can include, but are not limited to the fiber optic component types of LC, SC, ST, LCAPC, SCAPC, MTRJ, and FC. The ICU may be configured to connect to any number of remote units. One or more power supplies either contained with the ICU or associated with the ICU may provide power to the power distribution module in the ICU. The power distribution module can be configured to distribute power to remote units with or without voltage and current protections and/or sensing. The power distribution module contained in the ICU may be modular where it can be removed and services or permanently installed in the ICU.

Further, as used herein, it is intended that terms “fiber optic cables” and/or “optical fibers” include all types of single mode and multi-mode light waveguides, including one or more bare optical fibers, loose-tube optical fibers, tight-buffered optical fibers, ribbonized optical fibers, bend-insensitive optical fibers, or any other expedient of a medium for transmitting light signals. Many modifications and other embodiments set forth herein will come to mind to one skilled in the art to which the embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the description and claims are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. It is intended that the embodiments cover the modifications and variations of the embodiments provided they come within the scope of the appended claims and their equivalents. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.