(12) United States Patent
`US 6,362,908 B1
`(10) Patent N0.:
`Kimbrough et al. Mar. 26, 2002 (45) Date of Patent:
`
`
`
`‘USOO6362908B1
`
`(54)
`
`(75)
`
`MULTI-SERVICE ADAPTABLE OPTICAL
`NETWORK UNIT
`
`Inventors: Mahlon Danny Kimbrough, Bedford;
`John Matthes, Southlake; Barry Joe
`Ethridge, Forth Worth, all of TX (US)
`
`(73)
`
`Assignee: Marconi Communications, Inc.,
`Cleveland, OH (US)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`(22)
`
`(51)
`(52)
`
`(58)
`
`(56)
`
`Appl. No.: 09/203,409
`
`Filed:
`
`Dec. 2, 1998
`
`Int. Cl.7 ........................... H04B 10/00; H04J 14/00
`US. Cl.
`....................... 359/163; 359/109; 359/118;
`359/119
`Field of Search ................................. 359/163, 109,
`359/117, 118, 119, 125, 137, 167
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`............. 359/127
`
`9/1989 Kwa .......................... 359/163
`4,863,232 A *
`11/1989 Dyke et a1.
`4,881,225 A
`12/1989 Dyke
`4,888,765 A
`2/1990 Dillon
`4,903,292 A
`4,965,790 A * 10/1990 Nishino et al.
`4,967,193 A
`10/1990 Dyke et al.
`5,046,067 A
`9/1991 Kimbrough
`5,218,654 A *
`6/1993 Sauter ........................ 359/163
`5,263,081 A
`11/1993 Nightingale et al.
`5,267,122 A
`11/1993 Glover et al.
`5,287,344 A
`2/1994 Bye et a1.
`5,303,229 A
`4/1994 Withers et al.
`5,325,223 A
`6/1994 Bears
`5,349,457 A
`9/1994 Bears
`5,355,362 A
`10/1994 Gorshe et al.
`5,383,180 A
`1/1995 Kartalopoulos
`5,469,282 A
`11/1995 Ishioka
`
`5,500,753 A
`3/1996 Sutherland
`5,504,606 A
`4/1996 Frigo
`5,566,239 A
`10/1996 Garcia et al.
`5,572,347 A
`11/1996 Burton et al.
`5,600,469 A
`2/1997 Yamazaki
`5,608,565 A
`3/1997 Suzuki et al.
`5,640,387 A
`6/1997 Takahashi et al.
`5,729,370 A
`3/1998 Bernstein et al.
`5,781,320 A *
`7/1998 Byers ......................... 359/123
`5,784,377 A *
`7/1998 Baydar et al.
`370/463
`
`5,831,979 A * 11/1998 Byers ...............
`370/360
`2/1999 Durvasula et al.
`.......... 455/450
`5,870,676 A *
`5,926,472 A *
`7/1999 Byers ......................... 370/252
`5,982,741 A * 11/1999 Ethier
`..........
`370/389
`6,038,048 A *
`3/2000 Harris et al.
`..
`359/159
`6,091,729 A *
`7/2000 DOVe
`...............
`370/395
`6,147,485 A * 11/2000 Halliday et al.
`..
`324/1581
`FOREIGN PATENT DOCUMENTS
`
`
`
`WO
`
`9729585
`
`8/1997
`
`* cited by examiner
`
`Primary Examiner—Leslie Pascal
`(74) Attorney, Agent, or Firm—Jones, Day, Reavis &
`Pogue
`
`(57)
`
`ABSTRACT
`
`A multi-service, adaptable optical network unit (ONU) is
`disclosed for use in a fiber-to-the-curb (FTTC) digital loop
`carrier system, including a multi-service common card and
`a plurality of multi-media service cards that are connected to
`the common card using a card-link interface. The card-link
`interface is preferably a high-speed LVDS serial-bus con-
`nection that is organized in a star configuration such that
`each service card is connected to the multi-service common
`
`card using a separate point-to-point card-link. By eliminat-
`ing the traditional backplane structure found in present ONU
`designs, the present invention provides a scalable, adaptable,
`future-proof FTTC system that can transport present-day
`multi-media services as well as yet-to-be-defined future
`high-bandwidth applications.
`
`36 Claims, 8 Drawing Sheets
`
` PUHER PAIR
`(82
`
`24
`
`VOICE
`
`DATA
`
`VIDEO
`
`POHER
`
`DISE*S MX
`HOST
`IERMINAL
`
` °S28
`SINGLE FIBER
` 35
`
`
`[31:23"
`
`50
`
`
`
`g
`
`POTS
`
`DATA
`
`VIDEO
`
`Page 1 of 19
`
`VERIZON EXHIBIT 1005
`
`EAIUH
`GROUND
`
`Page 1 of 19
`
`VERIZON EXHIBIT 1005
`
`

`

`maPS”U
`
`1B
`
`m2mm
`
`om«:2Mega:mm:Am.mm,mEHEw,mWcm:s_Umilm,2$59.g.mlH
`
`ma:.Qa.§:Q._<~:§wE%W.%mmm.33$1.4qu
`
`Hm22::
`
`@—
`
`Page 2 of 19
`
`Page 2 of 19
`
`
`
`

`

`US. Patent
`
`Mar. 26, 2002
`
`Sheet 2 0f 8
`
`US 6,362,908 B1
`
`66
`
`68
`
`66
`
`66
`
`64
`
`64
`
`VA
`74
`
`
`
`
`
`Fig. 2A
`(PRIOR ART)
`
`Page 3 0f 19
`
`Page 3 of 19
`
`

`

`S”U
`
`m.
`
`r..a
`
`m
`
`M3m
`
`2mam.638
`
`
`mas“I.mammomma”:i.
`
`Mmm:5momTwe:8ii.-mm.
`
`wasdigs:2:
`
`ozwmmmmg__55%20:28fifiaéE:E<Es<Em___o20%a3mm
`
`
`
`PE
`
`Page 4 of 19
`
`US 6,362,908 B1
`
`mm.3
`
`
`
`25‘202?:
`
`
`
`mmas:2:muzon.
`
`$952228$3nga3a892:38;@532:mgismz538
`
`ommmmm
`
`Page 4 of 19
`
`
`
`

`

`2
`
`mI
`
`QMmm
`4;_m--mU.mp-D
`aow
`69DU
`mmmm:mmmhmagmmmm
`mmAm¢.mm.om..Afl
`
`
`
`U
`
`00f04whS
`
`US 6,362,908 B1
`
`.mv.mm.om.«_H\
`
`amid
`
`.2203So:
`
`z.25sz
`
`1
`
`m.5
`
`vm
`
`13mm
`MW)»;—./
`
`
`
`mu_mgo4<mpzmm
`
`a
`
`g
`
`E»
`
`Page 5 0f 19
`
`Page 5 of 19
`
`
`

`

`s”nu
`
`tm
`
`m
`
`“m5
`
`00
`
`US 6,362,908 B1
`
`who;
`
`<h<o
`
`82>
`
`15:;
`
`ozsomo
`
`
`n;mH<¢«use;
`r4<z_zmuhmwho;Hmoz
`
`Mmuu_o>
`
`".10..own:>
`2mmzom
`
`
`
`
`x:m*umfig<h<o
`
`Page 6 0f 19
`
`Page 6 of 19
`
`

`

`US. Patent
`
`hdar.26,2002
`
`Sheet6 0f8
`
`US 6,362,908 B1
`
`om‘\fl\‘.
`
`<._.<:when
`
`OO
`
`0O
`
`com
`
`
`
`momoo_
`
`mom
`
`Page 7 0f 19
`
`
`
`mmmmA4em1%Ammmm\.m_.59;m59:mSm:_Em:A59:Q?Qloglognamename$2m33?.
`
`Page 7 of 19
`
`
`

`

`US. Patent
`
`hdar.26,2002
`
`Sheet7 0f8
`
`US 6,362,908 B1
`
`
`
`
`
`who;uu<_zm~z_mzHA
`
`m\.mmmu<_mupzflquA
`
`
`
`4<_uwmmm.umHD
`
`Mmufi>mmmDm<umzHA
`
`
`
`mu_zm<uDm<uMZHJ
`
`oo_
`
`oo_
`
`
`
`¥z_4am<u
`
`mu<mzmp2_
`
`
`
` we“Immem<uwhom\mmu_>mmm«uph_4mmmm
`
`mu<gmmhz_mz_4
`
`Oma_>rwmo
`
`5;-
`
`x<ou
`
`m.5
`
`muufl>mmm_mm<mo_
`
`sz4gm<u
`
`Pu¥u<m
`
`Hmm<mo_
`
`z¥z_4
`
`
`
`
`
`om<u<_<Dom<u
`
`mwg_>mmmszJ=m<u
`
`cmHmm<mo_voA}mzHozm
`<_<:wu<_mmhz_oo_
`
`
`om_Dm<u
`
`mmzofiwwfiumHEEE
`m.umHD¥z~4Dm<umszA
`
`uw<¢mmF2__QMQWJ
`u_pmo om<u
`
`
`zozzou<p<oemo_>\mhom
`
`mm
`
`zm_ma4mz<
`
`memo
`
`
`
`kHz:Hmmh
`
`mu<uzuhzfi
`
`zMJAOmHzou
`
`mmzom
`
`awhmu>20u
`
`mz~w2_m
`
`mo_<zmzum
`
`om
`
`0
`
`mm
`
`mmem
`
`mm
`
`muzom
`
`zH<m
`
`Page 8 0f 19
`
`Page 8 of 19
`
`
`
`

`

`US. Patent
`
`h43r.26,2002
`
`Sheet8 0f8
`
`US 6,362,908 B1
`
`muH>mmm
`
`om<u
`
`mv_Amo<m4«HmamHmmHHmmhmoms
`
`vflfi
`
`mo~<mu2uo
`
`
`
`
`
`mm_.mo<u4m.zmzhumazaomo
`
`8_}\
`
`om_.vo.mo
`
`«2mi?m+
`
`om_mh40>0.:
`
`m2mZo>mvl
`
`mmzom
`
`muhmm>zou
`
`
`
`
`
`Ov_mo<h40>mz_mszQZHDZEm
`
`o“—
`
`m__
`
`Page 9 0f 19
`
`
`
`Amo<u4m.<h<om>_uumm
`
`
`
`
`
`.mo<u4m.xquuw>_uumm
`
`H_z:
`
`
`
`¥z_4am<u
`
`om_\ofi_
`
`©.3
`
`
`
`
`
`.mD<u4m.azsomauflmog
`
`
`
`
`
`.mo<m4NH¥u04u_~zmz<zpM¥2b41wwpzmm
`
`
`
`.mo<u4m.<H<oh_zmz<mpmUXMJmHPJDZ
`
`
`
`
`
`Page 9 of 19
`
`
`
`
`
`

`

`US 6,362,908 B1
`
`1
`MULTI-SERVICE ADAPTABLE OPTICAL
`NETWORK UNIT
`
`BACKGROUND OF THE INVENTION
`
`The present invention is related to the field of fiber-to-
`the-curb (“FTTC”) digital loop carrier (“DLC”) systems for
`communicating information in the local access loop between
`a central office switching station and a plurality of customer
`locations.
`In particular, a novel optical network unit
`(“ONU”) for use with such an FTTC system is described, in
`which the ONU includes at least one multi-service common
`
`card coupled to a plurality of service cards via a plurality of
`high-speed serial interconnections. The high-speed serial
`interconnections are preferably arranged in a separate point-
`to-point “star” configuration in which each service card
`includes a separate high-speed point-to-point serial interface
`with the one or more multi-service common cards. A family
`of adaptable multi-service common cards and a scalable
`FTTC system for delivering present and future multi-media
`services in the local loop are also disclosed.
`By eliminating the traditional backplane found in present
`ONUs,
`the ONU of the present
`invention provides a
`modular, easily-reconfigurable (i.e. adaptable) architecture
`that extends the operating life of the ONU far beyond that of
`traditional ONU designs, and thus enables the system to
`adapt to unknown services that may or may not be antici-
`pated at the time of installation. Due to the inherent limita-
`tions of a backplaned ONU, such adaptability to future
`services is not possible. Using the features and principles of
`the present
`invention, a future-proof, expandable FTTC
`system can be installed that
`is capable of providing a
`multitude of multi-media services over a single fiber-optic
`connection, such as telephony, high-speed data, CATV,
`video-on-demand, as well as any number of future services
`that may require extremely high-bandwidth.
`In a typical DLC system, the digital transport capabilities
`of the phone network are extended from the central office
`switch into a particular neighborhood or business location.
`Aremote digital (“RDT”) is placed at a remote location from
`the central office and is connected to it via a fiber-optic
`cable, or some other high-bandwidth connection. The
`remote digital
`terminal
`receives PCM-modulated voice
`information from the central office switch, converts the
`digital PCM signals into analog voice signals, and routes the
`analog voice signals to a particular customer location via a
`plurality of line-cards (or service cards) that connect the
`RDT to the customer’s equipment. Similarly,
`the RDT
`converts analog voice information from the customer to a
`digital PCM format for transport back to the central office
`switch. An example of a digital loop carrier system is set
`forth in US. Pat. No. 5,046,067 (“the ’067 patent”), which
`is assigned to the assignee of the present invention. The
`teaching of this patent
`is hereby incorporated into the
`present application by reference.
`An FTTC system is an extended version of the DLC
`system described above, in which the fiber-optic capabilities
`are extended further into the local loop by fiber-coupling a
`plurality of ONU telecommunication terminals to the RDT
`(which is then referred to as a Host Digital Terminal, or
`HDT), wherein the ONUs are located very close to the
`customer locations. An example FTTC system is set forth in
`FIG. 1, discussed in more detail below. The system shown
`in FIG. 1 is also described in US. patent. application Ser.
`No. 08/794,723,
`titled “Distributed Ethernet Hub” (the
`“’723 application”). This application is commonly assigned
`to the assignee of the present invention and the teaching of
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`this application is hereby incorporated into this disclosure by
`reference. As shown in FIG. 1, in a typical FTTC system the
`RDT is converted into an HDT, which, in many respects, is
`similar to the RDT, except that the HDT is further connected
`to a plurality of ONU telecommunication terminals via
`fiber-optic cable. The HDT includes appropriate circuitry
`and programming for routing signals to and from the plu-
`rality of ONUs and the central office switching station.
`The ONUs are relatively small pedestal terminals that are
`physically located in close proximity to a customer’s
`location, such as 500' or less. By placing the ONU in close
`physical proximity to the customer, high-bandwidth com-
`munications can be managed through the ONU over tradi-
`tional wiretypes. Each ONU typically services a plurality of
`customers, such as 4 to 8, although, in the future, more
`customers may be serviced from a single ONU. The ONU
`provides many functions. It converts optical signals from the
`HDT into appropriate electrical signals that correspond to
`the customer’s equipment, such as analog phone signals, or
`high-speed data signals. It provides voltage surge protection
`for the physical connections to the customer’s premises,
`such as twisted-pair copper or coaxial cable. It provides
`built-in test capabilities so that the lines to the customer’s
`premises can be tested from the central office. It receives
`power from the HDT, and converts the received power into
`a conditioned power level that serves the ONU circuitry, as
`well as many other functions.
`Presently, FTTC systems including ONUs are typically
`deployed for Plain Old Telephone Service (“POTS”), with
`the intention of getting fiber-optic cable close to the cus-
`tomer’s premises so that present and future broadband
`services can be provided as they are defined, or as they
`become economically feasible. One example of these types
`of broadband services is high-speed Internet access. The
`”723 application provides a solution to delivering these types
`of services using presently available ONU technology. Other
`types of broadband services include CATV, video-on-
`demand, video conferencing, xDSL, interactive television,
`digital TV and radio, ISDN, as well as many other yet to be
`defined high-bandwidth applications. Companies seeking to
`deploy FTTC systems would like to be sure that future
`services, which have not even been defined, can still be
`handled by the FTTC system hardware in place. Thus, a
`future-proof architecture is desirable for the ONU, which
`provides the critical link between the FTTC system and the
`customer premesis. Presently known ONUs are not future-
`proof.
`Presently known ONUs are not capable of being future-
`proof because they utilize a backplane architecture. FIGS.
`2A and 2B, discussed in more detail below, set forth such an
`ONU incorporating a backplane architecture. In these types
`of ONUs, the common cards and service cards plug into a
`circuit-board backplane that includes a plurality of connec-
`tors for mating to corresponding connectors on the common
`or service cards and one or more electrical busses that
`
`connect the cards together. The one or more busses are metal
`interconnections (or traces) embedded in the backplane
`circuit board. The cards communicate with each other pri-
`marily via the backplane traces. Because the structure of the
`backplane inherently limits the services that can be handled
`by the ONU, any backplane architecture is not capable of
`being future-proof.
`There are many problems associated with using a back-
`plane structure. First, there is no modularity built into the
`system, since the position and spacing of the backplane
`connectors is mechanically fixed. Thus, the backplane can
`only accept circuit cards of a particular dimension and
`
`Page 10 of 19
`
`Page 10 of 19
`
`

`

`US 6,362,908 B1
`
`3
`width. Second, the bandwidth of the backplane is limited by
`its electrical properties. These electrical properties that limit
`the bandwidth include the impedance of the interconnections
`between the circuit boards and the backplane and the imped-
`ance limitations of the metallization traces that connect the
`
`connectors together. In addition, termination resistors may
`limit
`the speed of the backplane bus. Because of these
`physical and electrical limitations, at higher frequencies it
`becomes very difficult to accurately distribute any type of
`clocking (or other data) signals over the backplane, due to
`skewing of the signals that may render the system inoper-
`able.
`
`In summary, it is not feasible to design a backplane ONU
`that is future-proof. Unless the operator of the FTTC system
`is willing to retrofit the ONUs with a new backplane every
`3 or 4 years (a very unlikely scenario given the large labor
`and materials costs involved), the entire system is essentially
`bandwidth-limited by the structure of the ONU backplane
`the moment
`it
`is installed in the field. This is a very
`undesirable reality for the customer spending millions of
`dollars to install an FTTC system.
`In addition to the drawing figures set forth below, other
`presently known ONUs are described in US. Pat. Nos.
`5,500,753 to Sutherland, 5,600,469 to Yamazaki, and 5,303,
`229 to Withers. Each of these presently known ONU sys-
`tems includes a backplane architecture and thus suffers from
`the many disadvantages noted above. See, for example, FIG.
`2 of the ”753 patent and FIGS. 1A/1B of the ’469 patent. The
`ONUs described in these patents are not future-proof, are not
`readily adaptable, do not provide the ability to handle a
`multitude of services, and therefore do not satisfy the present
`need in this field for an ONU capable of being used in an
`FTTC system for many years into the future.
`Thus, there remains a general need in this field for a
`multi-service, adaptable ONU that does not employ a back-
`plane architecture and thus avoids the many disadvantages
`associated with designing a future-proof backplane.
`There remains a more particular need for such an ONU in
`which a plurality of different types of service cards can be
`supported via a single common card.
`There remains yet another need for a multi-service FTTC
`system in which telephony, high-speed data, video and other
`presently undefined high-bandwidth services can be chan-
`neled through an adaptable ONU system without undue
`costs for retrofitting and installation.
`There remains still another need for an ONU in which
`
`individual service cards can be replaced in the ONU without
`effecting the other services provided by the ONU.
`There remains still another need for an ONU that can
`
`support a family of modular common cards, wherein the
`common card capabilities build from simple telephony cards
`to more complex telephony/data/video cards, and beyond.
`Still another need remains for a preferred method and
`structure of interconnecting the one or more common cards
`and the plurality of service cards in a backplane-less ONU
`so that bandwidth and flexibility are maximized.
`
`SUMMARY OF THE INVENTION
`
`invention overcomes the problems noted
`The present
`above and satisfies the needs in this field for a multi-service,
`adaptable optical network unit for use in a FTTC system.
`The ONU of the present invention includes a multi-service
`common card and a plurality of multi-media service cards
`that are connected to the common card using a card-link
`interface. The card-link interface is preferably a high-speed
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`LVDS serial-bus connection organized in a star configura-
`tion such that each service card is connected to the multi-
`service common card using a separate point-to-point card-
`link. By eliminating the traditional backplane structure
`found in present ONU designs, the present invention pro-
`vides a scalable, adaptable, future-proof FTTC system that
`can transport present-day multi-media services as well as
`yet-to-be-defined future high-bandwidth applications.
`One embodiment of the present
`invention provides a
`fiber-to-the-curb digital loop carrier system for transporting
`multi-media information in the local loop between a central
`office switching station and a plurality of customer locations,
`comprising: a plurality of host digital terminals coupled to
`the central office switching station by fiber-optic connec-
`tions; and at least one optical network unit coupled to a host
`digital terminal by fiber-optic connections, wherein each
`optical network unit comprises: at least one multi-service
`common card including a fiber optic-interface, a service
`multiplexer, and a plurality of card-link interface circuits; a
`plurality of service cards including circuitry for processing
`a particular multi-media service, and at least one card-link
`interface circuit; and a plurality of card-links coupling the
`plurality of service cards to the multi-service common card.
`Another embodiment of the present invention provides an
`optical network unit for use in a fiber-to-the-curb system,
`comprising: a multi-service common card; a plurality of
`service cards; and a plurality of serial interface connections
`for communicating information between the common card
`and the plurality of service cards. The plurality of serial
`interface connections are preferably connected in a star
`configuration.
`Still another embodiment of the present invention pro-
`vides a multi-service common card for use in an optical
`network unit of a fiber-to-the-curb digital
`loop carrier
`system, comprising: a fiber optic interface; a service multi-
`plexer; and a plurality of card-link interface circuits.
`Another embodiment provides an optical network unit,
`comprising: a multi-service common card and a plurality of
`service cards, wherein the multi-service common card
`includes means for receiving and transmitting optical signals
`and for converting the optical signals into corresponding
`electrical signals, means for routing the corresponding elec-
`trical signals to the plurality of service cards, and a plurality
`of card-links for coupling the multi-service common card to
`the plurality of service cards.
`Apreferred system-level method of the present invention
`provides a method of transporting multi-media information
`in a fiber-to-the-curb digital loop carrier system, comprising
`the steps of: receiving multi-media information at a central
`office switching station; converting the multi-media infor-
`mation into optical signals and routing the optical signals to
`a plurality of host digital terminals via a plurality of fiber
`optic cables; receiving the multi-media optical signals at the
`host digital terminals and routing the signals to a plurality of
`optical network units via a plurality of fiber optic cables;
`receiving the multi-media optical signals at the plurality of
`optical network units and converting the signals into corre-
`sponding electrical signals; and routing the electrical signals
`to corresponding multi-media service cards within the opti-
`cal network unit via a plurality of high-speed serial interface
`circuits that couple the multi-media service cards to one or
`more multi-service common cards.
`
`Other embodiments of the present invention will become
`apparent when reviewing the detailed description of the
`drawings set forth below.
`The present invention provides many advantages over
`presently known ONUs. Not all of these advantages are
`
`Page 11 of 19
`
`Page 11 of 19
`
`

`

`US 6,362,908 B1
`
`5
`simultaneously required to practice the invention as claimed,
`and the following list is merely illustrative of the types of
`benefits that may be provided, alone or in combination, by
`the present
`invention. These advantages include:
`(1) a
`future-proof architecture that can accommodate a wide
`range of applications and services, including those that have
`yet
`to be defined, and which can scale from simple
`telephony, video or data-only applications to a combination
`of these three services and beyond; (2) no backplane limi-
`tations on bandwidth or interconnection; (3) scalable inter-
`connection to support future services; (4) a preferred star
`interconnection scheme that allows each service card to
`
`operate independently from the other service cards and at a
`variety of speeds; (5) adaptable, modular, flexible, and low
`cost; (6) low power operation; (7) variable card-spacing
`enclosure for holding cards of varying degrees of thickness;
`(8) preferred low-voltage differential signaling (“LVDS”) to
`support scalable high-speed serial
`interface between the
`common card(s) and the plurality of service cards;
`(9)
`scalable multi-service common card capable of interfacing
`to a variety of service cards using a plurality of high-speed
`serial
`interface connections; and (10) a special-purpose
`line-card carrier that enables the use of backplane-type
`service cards with the present invention.
`These are just a few of the many advantages of the present
`invention, as described in more detail below. As will be
`appreciated, the invention is capable of other and different
`embodiments, and its several details are capable of modifi-
`cations in various respects, all without departing from the
`spirit the invention. Accordingly, the drawings and descrip-
`tion of the preferred embodiments set forth below are to be
`regarded as illustrative in nature and not restrictive.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention satisfies the needs noted above as
`will become apparent from the following description when
`read in conjunction with the accompanying drawings
`wherein:
`
`FIG. 1 is a block diagram of a presently known FTTC
`system for delivering voice and high-speed data in the local
`loop;
`FIG. 2A is a schematic of a presently known ONU card
`cage for receiving the common cards and service cards into
`a backplane structure;
`FIG. 2B is a block diagram of a presently known back-
`plane bus interconnection for the ONU shown in FIG. 2A;
`FIG. 3 is a block diagram of a preferred FTTC system
`according to the present
`invention for delivering voice,
`high-speed data, CATV, video-on-demand, and any number
`of other future high-bandwidth services;
`FIG. 4A is a block diagram showing the preferred con-
`nections between the HDT and one of the ONUs according
`to the present invention in which a preferred multi-service
`common card is coupled to a plurality of service cards in a
`preferred star configuration;
`FIG. 4B is a schematic of a preferred card cage without
`a backplane for receiving the multi-service common card
`and the plurality of service cards as shown in FIG. 4A;
`FIG. 5 is a more detailed block diagram of the preferred
`multi-service common card showing the preferred star con-
`figuration interconnections to the plurality of service cards
`via a plurality of card-links; and
`FIG. 6 is a more detailed block diagram showing a
`preferred series of connections between the common card
`and one of the service cards forming one of the card-links.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`Referring now to the drawings, FIGS. 1, 2A and 2B set
`forth a presently known FTTC system and a presently
`known backplane-type ONU. Specifically, FIG. 1 is a system
`diagram, FIG. 2A is a schematic of an ONU card cage for
`receiving the common cards and service cards into a back-
`plane structure, and FIG. 2B is a block diagram of the
`backplane bus interconnection for the ONU shown in FIG.
`2A.
`
`The FTTC system 10 shown in FIG. 1 includes a plurality
`of HDTs 14 coupled to a central office switching station 12
`via fiber-optic interconnections 24. An example of such an
`HDT is the DISC*S® digital loop carrier platform manu-
`factured by Reltec Corp. of Bedford, Texas. Each HDT 14
`is coupled to a plurality of ONUs 26, also via fiber-optic
`interconnections 28. The ONUs 26 are then coupled to the
`customer premises 30, where the signals from the ONU are
`terminated at customer equipment, such as a computer 32 or
`telephone 34. The connections from the ONU 26 to the
`customer equipment can be, for example, coaxial cable 36 or
`twisted-pair copper 38.
`The central office switching station 12 may include a local
`digital switch 20 or a router 22. The local digital switch 20
`couples the central office station 12 to the PSTN for deliv-
`ering PCM-type voice signals, such as DS-O or DS-1 signals,
`and the router 22 couples the station 12 to the Internet for
`delivering packet data signals, such as Ethernet-type data
`packets
`the central office switching station 12
`Operationally,
`receives PCM voice information and packet data from the
`PSTN and the Internet, processes this information in some
`manner, converts the information from electrical signals into
`optical signals, and then routes it to the correct HDT 14 via
`one or more fiber-optic interconnections 24. Each HDT 14
`then further processes the information to determine what
`ONU to send the information to via fiber-optic connections
`28.
`The ONU 26 converts the voice and data information
`
`from the HDT from optical to electrical signals, such as
`analog voice signals or Ethernet packet data signals. It then
`routes these signals to the proper customer premises equip-
`ment 32, 34 via interconnections 36, 38. The ONU is
`typically located within 500 feet of a customer location 30,
`and thus typically services 8—10 customers. Similarly, the
`customer premises equipment 32, 34 transmits signals to the
`local ONU 26, where they are converted into optical signals
`and combined with signals from other customer’s
`equipment, and then transmitted over fiber-optic cable 28 to
`a respective HDT 14. The HDT 14 combines the signals
`from many ONUs 26 and transmits the combined informa-
`tion over fiber-optic cable 24 back to the central office
`switching station 12, where the information is processed,
`converted back to an equivalent electrical signal level, and
`routed to either the PSTN 16 or to the Internet 18, depending
`on the information type.
`FTTC systems as described in FIG. 1 are not cheap. They
`require a great deal of planning, capital,
`regulatory
`approvals, and manpower to implement. Therefore, compa-
`nies that want to install this type of equipment want it to last
`for many years, in some cases up to 20-years from the date
`of installation. Thus, a future-proof system is desirable.
`Presently, there are no known systems that provide a future-
`proof architecture that could conceivably provide for the yet
`to be defined wide-bandwidth services that may be imple-
`mented 20-years into the future. The primary reason that
`known FTTC systems cannot guarantee their viability into
`
`Page 12 of 19
`
`Page 12 of 19
`
`

`

`US 6,362,908 B1
`
`7
`the future is because these system utilize an ONU architec-
`ture that includes a backplane structure.
`FIGS. 2A and 2B set forth a presently known ONU
`incorporating a backplane architecture. Other known ONUs,
`such as described in the Sutherland, Yamazaki, and Withers
`patents, mentioned above, all include a backplane structure
`at the ONU for physically and electrically connecting the
`common card(s) and the service cards. In these types of
`ONUs,
`the common cards and service cards plug into a
`circuit-board backplane 64 that includes a plurality of con-
`nectors 66 for mating to corresponding connectors on the
`common or service cards and one or more electrical busses
`
`68A—E that connect the cards together. The one or more
`busses are metal interconnections (or traces) 68 embedded in
`the backplane circuit board 64. The cards communicate with
`each other primarily via the backplane traces. Because the
`structure of the backplane 64 inherently limits the services
`that can be handled by the ONU, any backplane architecture
`is not capable of being future-proof
`FIG. 2A shows the card-cage 62 of a presently known
`ONU 26. One or more backplanes 64 are located at the back
`of the card-cage 62. The backplane 64 is a circuit board that
`includes a plurality of connectors 66, such as finger-type
`connectors or pin-connectors, for mating with a correspond-
`ing connector on the circuit cards 70, 72, 74, 76, 78 that plug
`into the one or more backplanes 64. The backplane 64 also
`includes a
`large number of metal
`traces 68 (or
`interconnections) that may be embedded in one or more
`metallization layers in the circuit board. These traces 68
`form one or more electrical busses that connect the connec-
`
`tors 66 together and form the backplane bus-structure of the
`ONU 26. The backplane may also include termination
`resistors that terminate the various bus interconnections 68.
`
`FIG. 2B shows a block diagram of a presently known
`backplane bus interconnection for the ONU shown in FIG.
`2A. This ONU 26 includes a plurality of cards that plug into
`the backplane 64, such as an optical interface unit 74 for
`coupling to the optical fiber 28 and converting signals from
`optical-to-electrical and vice-versa, a broadband common
`card 76 for processing broadband signals, such as high-
`speed Internet data or DS-1 telephony information, and for
`routing the data to the proper service card 78, a power
`converter unit 72 for coupling to one or more power pair 82
`and for providing regulated power to the ONU, and a
`narrowband common card 80 for processing PCM voice
`information and for routing the information to the proper
`service card 70. The broadband service cards 78 transport
`information to/from the customer premises equipment 32 via
`coaxial cable 36, and the narrowband service cards 70
`transport information to/from the customer premises equip-
`ment 34 via twisted-pair copper lines 38.
`Aplurality of electrical busses formed by the traces 68 of
`the backplane structure 64 connect the common, service and
`other cards together in the prior art ONU. These busses may
`include, for example, a dual DS-1 bus 68A, a processor bus
`68B, a power bus 68C, a narrowband data bus 68D and a
`test/PCM bus 68E. Each of these busses includes a plurality
`of metal traces 68 that are designed to distribute information
`and signals between the cards through the backplane con-
`nectors 66.
`
`There are many problems associated with using a back-
`plane structure 64 as shown in FIGS. 2A/2B. First,
`the
`system is not modular or expandable, since the position and
`spacing of the backplane connectors 66 is mechanically
`fixed. Thus, the backplane 64 can only accept circuit cards
`of a particular dimension and width. Second, the bandwidth
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`of the backplane 64 is limited. The impedance of the
`interconnections 66 between the circuit boards and the
`backplane 64, as well as the impedance limitations of the
`metallization traces 68 that connect
`the connectors 66
`
`together (and form the variety of busses 68A—E) inherently
`limit the bandwidth that information can be transported over
`the backplane bus. Termination resistors may also limit the
`speed of the backplane bus. Because of these physical
`limitations of the backplane structure, at higher frequencies
`it becomes very difficult to accurately distribute any type of
`clocking signals over the backplane. This results in unde-
`sirable skewing of signals that render the system inoperable.
`When a backplane-type ONU is designed, it is purposely
`provided with a backplane structure that can transport more
`information than is required at
`the time of installation.
`However, it is impossible to accurately predict the services
`that will be required in a FTTC system 5 or 10 years into the
`future, let alone 20 years, which is the goal from the FTTC
`customer’s perspective. This is part