Source: http://www.google.com/patents/US6947623?dq=7,339,580
Timestamp: 2014-07-11 16:08:28
Document Index: 82172331

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US6947623 - Signals and methods for increasing reliability in optical network equipment - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsMethods, apparatus and systems for regenerating, monitoring and bridging optical signals through an optical cross-connect switch to provide increased reliability. A self testing method, apparatus and system for an optical cross-connect switch. An optical-to-electrical-to-optical converter (O/E/O) is...http://www.google.com/patents/US6947623?utm_source=gb-gplus-sharePatent US6947623 - Signals and methods for increasing reliability in optical network equipmentAdvanced Patent SearchPublication numberUS6947623 B2Publication typeGrantApplication numberUS 10/650,543Publication dateSep 20, 2005Filing dateAug 28, 2003Priority dateNov 2, 1999Fee statusPaidAlso published asCA2389527A1, EP1228588A2, US6650803, US6813407, US6944364, US20040037553, US20040076365, US20040258408, WO2001033746A2, WO2001033746A3Publication number10650543, 650543, US 6947623 B2, US 6947623B2, US-B2-6947623, US6947623 B2, US6947623B2InventorsRajiv Ramaswami, Robert R. WardOriginal AssigneeNortel Networks LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (105), Non-Patent Citations (18), Referenced by (13), Classifications (35), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetSignals and methods for increasing reliability in optical network equipmentUS 6947623 B2Abstract Methods, apparatus and systems for regenerating, monitoring and bridging optical signals through an optical cross-connect switch to provide increased reliability. A self testing method, apparatus and system for an optical cross-connect switch. An optical-to-electrical-to-optical converter (O/E/O) is provided in an optical cross-connect switch to provide optical-electrical-optical conversion. I/O port cards having an optical-to-electrical-to-optical converter are referred to as smart port cards while I/O port cards without an optical-to-electrical-to-optical converter are referred to as passive port cards. Test port/monitor cards are also provided for testing optical cross-connect switches. Methods, apparatus and systems for performing bridging, test access, and supporting redundant optical switch fabrics are also disclosed.
1. Data signal propagation in an optical network equipment for increased reliability, comprising:
a first data signal embodied in a first optical signal on a first optical path in the optical network equipment; the first data signal simultaneously embodied in a second optical signal on a second optical path in the optical network equipment; wherein the first optical path is different from the second optical path; wherein if the first optical path should fail then the second optical signal on the second optical path can provide continued first data signal propagation in the optical network equipment, or if the second optical path should fail then the first optical signal on the first optical path can provide continued first data signal propagation in the optical network equipment. 2. The data signal propagation of claim 1 further comprising:
the first data signal simultaneously embodied in a third optical signal on a third optical path in the optical network equipment; wherein the third optical path differs from the first and second optical paths; and wherein if the first and second optical paths should then the third optical signal on the third optical path can provide continued first data signal propagation in the optical network equipment. 3. The data signal propagation of claim 1 further comprising:
a second data signal embodied in a fourth optical signal on a fourth optical path in the optical network equipment, the second data signal differing from the first data signal; the second data signal simultaneously embodied in a fifth optical signal on a fifth optical path in the optical network equipment; wherein the fourth optical path differs from the fifth optical path; and wherein if the fourth optical path should fail then the fifth optical signal on the fifth optical path can provide continued second data signal propagation in the optical network equipment, or if the fifth optical path should fail then the fourth optical signal on the fourth optical path can provide continued second data signal propagation in the optical network equipment. 4. The data signal propagation of claim 1 wherein
the optical network equipment is an optical bridge, an optical router, an optical cross-connect switch, an optical hub, an optical node, an optical concentrator, or other networking equipment accepting a data signal embodied in an optical signal. 5. A method of increasing reliability in optical network equipment, the method comprising:
converting an input optical signal in the optical domain into an electrical signal in the electrical domain; concurrently converting the electrical signal in the electrical domain into a first optical signal and a second optical signal in the optical domain; routing the first optical signal and the second optical signal respectively over two differing optical paths in the optical network equipment; similarly processing the first optical signal and the second optical signal through the optical network equipment to generate a first processed optical signal and a second processed optical signal respectively; and selecting the stronger signal of either the first processed optical signal or the second processed optical signal as the output optical signal of the optical network equipment. 6. The method of claim 5 wherein
the electrical signal in the electrical domain is simultaneously converted into the first optical signal and the second optical signal in the optical domain by an electrical to optical converter and an optical splitter. 7. The method of claim 5 wherein
the optical network equipment is an optical cross-connect switch. 8. The method of claim 5 wherein
the selecting selects the first processed optical signal as the output optical signal because the second processed optical signal has a weaker signal strength than the first processed optical signal. 9. The method of claim 5 wherein
the selecting selects the first processed optical signal as the output optical signal because the second processed optical signal is unavailable for selection by the selecting as a result of a failure in an optical path and the processing of the second optical signal failing to generate the second processed optical signal. 10. The method of claim 9 wherein
the second processed optical signal is unavailable for selection by the selecting as a result of a failed component in the optical path over which the second optical signal is routed in the optical network equipment. 11. The method of claim 5 wherein
the selecting of either the first processed optical signal or the second processed optical signal includes converting the first processed optical signal in the optical domain into a first processed electrical signal in the electrical domain, converting the second processed optical signal in the optical domain into a second processed electrical signal in the electrical domain, selecting either the first processed electrical signal or the second processed electrical signal as an output electrical signal, and converting the output electrical signal in the electrical domain into the output optical signal in the optical domain. 12. The data signal propagation of claim 1, wherein
if the first optical path fails, or the second optical path fails, or both the first and second optical paths fail, an alarm signal embodied in an electrical signal from the optical network equipment to signal a failure of an optical path. 13. The data signal propagation of claim 12 wherein
if the first optical path should fail, the alarm signal embodied in the electrical signal from the optical network equipment signals a failure of the first optical path. 14. The data signal propagation of claim 12 further comprising:
the first data signal simultaneously embodied in a third optical signal on a third optical signal path in the optical network equipment; wherein the third optical path differs from the first and second optical paths; and wherein if both the first and second optical paths should fail, the alarm signal embodied in the electrical signal from the optical network equipment signals a failure of both the first and second optical paths, and the third optical signal on the third optical path can provide continued first data signal propagation in the optical network equipment. 15. The data signal propagation of claim 14 further comprising:
the first data signal simultaneously embodied in a fourth optical signal on a fourth optical signal path in the optical network equipment; wherein the fourth optical path differs from the first, second and third optical paths; and if the first, second and third optical paths should fail, the alarm signal embodied in the electrical signal from the optical network equipment signals a failure of the first, second and third optical paths, and the fourth optical signal on the fourth optical path can provide continued first data signal propagation in the optical network equipment. 16. The data signal propagation of claim 1 wherein
the optical network equipment is an optical bridge, an optical router, an optical cross-connect switch, an optical hub, an optical node, an optical concentrator, or other networking equipment accepting a data signal embodied in an optical signal. 17. The data signal propagation of claim 1 wherein
a portion of the first optical path is in a first optical switch fabric of the optical network equipment, and a portion of the second optical path is in a second optical switch fabric of the optical network equipment. 18. A method of data signal propagation in an optical network equipment for increased reliability, the method comprising:
simultaneously embodying a plurality of data signals respectively into a first plurality of optical signals and a second plurality of optical signals, each data signal of the plurality of data signals being different; respectively propagating the first plurality of optical signals over a first plurality of optical paths in the optical network equipment; respectively propagating the second plurality of optical signals over a second plurality of optical paths in the optical network equipment, the second plurality of optical paths differing from the first plurality of optical paths; wherein if one of the optical paths in the first plurality of optical paths should fail then one of the second plurality of optical signals on a respective one of the second plurality of optical paths can provide continued data signal propagation in the optical network equipment, and if one of the optical paths in the second plurality of optical paths should fail then one of the first plurality of optical signals on a respective one of the first plurality of optical paths can provide continued data signal propagation in the optical network equipment. 19. The method of claim 18, wherein
a portion of the first plurality of optical paths are in a first optical switch fabric of the optical network equipment, and a portion of the second plurality of optical paths are in a second optical switch fabric of the optical network equipment. 20. The method of claim 18, wherein
the optical network equipment is an optical bridge, an optical router, an optical cross-connect switch, an optical hub, an optical node, an optical concentrator, or other networking equipment accepting a data signal embodied in an optical signal. 21. The method of claim 18, further comprising:
if any optical path fails in the first plurality of optical paths, signaling a failure of an optical path in the first plurality of optical paths by transmitting an alarm signal embodied in an electrical signal out from the optical network equipment; if any optical path fails in the second plurality of optical paths, signaling a failure of an optical path in the second plurality of optical paths by transmitting an alarm signal embodied in an electrical signal out from the optical network equipment; and if optical paths fail in both the first and second plurality of optical paths, signaling a failure of the optical paths in both the first plurality of optical paths and the second plurality of optical paths by transmitting an alarm signal embodied in an electrical signal out from the optical network equipment. 22. The method of claim 18, further comprising:
if one of the optical paths in the first plurality of optical paths fails, selecting the respective optical signal of the second plurality of optical signals on the respective one of the second plurality of optical paths as an output optical signal for the respective data signal to provide continued data signal propagation in the optical network equipment; and if one of the optical paths in the second plurality of optical paths fails, selecting the respective optical signal of the first plurality of optical signals on the respective one of the first plurality of optical paths as the output optical signal for the respective data signal to provide continued data signal propagation in the optical network equipment.
CROSS REFERENCE TO RELATED APPLICATIONS �This non-provisional U.S. (U.S.) patent application claims the benefit of and is a divisional of U.S. patent application Ser. No. 09/704,439 filed on Nov. 1, 2000 by inventors Rajiv Ramaswami, et al., entitled �METHOD AND APPARATUS FOR OPTICAL TO ELECTRICAL TO OPTICAL CONVERSION IN AN OPTICAL CROSS-CONNECT SWITCH�, now U.S. Pat. No. 6,650,803.
The parent patent application, U.S. patent application Ser. No. 09/704,439, claims the benefit of U.S. Provisional Patent Application No. 60/162,936 entitled �OPTICAL CROSSCONNECT WITH OPTICAL TO ELECTRICAL CONVERTERS� filed on Nov. 2, 1999 by inventor Rajiv Ramaswami; and also claims the benefit of U.S. Provisional Patent Application No. 60/170,094 entitled �OPTICAL CROSSCONNECT WITH BRIDGING, TEST ACCESS AND REDUNDANCY� filed on Dec. 10, 1999 by inventors Rajiv Ramaswami and Robert Ward; and also claims the benefit of U.S. Provisional Patent Application No. 60/170,095 entitled �OPTICAL CROSSCONNECT WITH LOW-LOSS BRIDGING, TEST ACCESS, AND REDUNDANCY� filed on Dec. 10, 1999 by inventors Steven Clark and Rajiv Ramaswami; and also claims the benefit of U.S. Provisional Patent Application No. 60/170,093 entitled �1+1 OPTICAL PROTECTION USING OPTICAL CROSSCONNECTS� filed on Dec. 10, 1999 by inventors Rajiv Ramaswami and Robert Ward; and also claims the benefit of U.S. Provisional Patent Application No. 60/170,092 entitled �SIGNALING INTERFACE BETWEEN OPTICAL CROSSCONNECT AND ATTACHED EQUIPMENT� filed on Dec. 10, 1999 by inventor Rajiv Ramaswami; and also claims the benefit of U.S. Provisional Patent Application No. 60/186,108 entitled �1:N PROTECTION BETWEEN CLIENTS AND ALL-OPTICAL CROSSCONNECTS� filed on Mar. 1, 2000 by inventors Kent Erickson, Subhashini Kaligotla, and Rajiv Ramaswami; and also claims the benefit of U.S. Provisional Patent Application No. 60/200,425 entitled �OPTICAL CROSSCONNECT SYSTEM� filed on Apr. 28, 2000 by inventors Rajiv Rarnaswami, Steve Tabaska, and Robert Ward.�
Moreover, as shown in FIG. 6, upon receiving an incoming light signal over an optical fiber link 420, the I/O port module 215, performs a bridging operation by splitting the incoming light signal into multiple (two or more) bridged light signals for routing to the first and second optical switch cores 240 and 260. The bridged light signals are routed through an internal optical interface 425 featuring optical fiber ribbon links 430 and 440. For this embodiment, the �optical fiber ribbon links� are ribbon cables having multiple optical fiber lines (e.g., two lines from each I/O port). The first optical switch core 240 provides a primary optical path. The second optical switch core 260 provides a redundant optical path in the event the first optical switch core 240 is not operating properly. The optical switch cores 240 and 260 route the bridged light signals to a selected port of a destination I/O port module (e.g., I/O port module 215 d) via optical fiber ribbon links 450 and 460.
Upon receiving light signals from both the first and second optical switch cores 240 and 260, the I/O port module 215 s provides small percentage optical tap signals of the received light paths to the respective servo modules, which in turn determine light signal quality. The respective servo modules will convey light signal quality for each respective light path to the I/O port module, using a digital protocol over an electrical communication link 505 to the I/O port module as shown in FIG. 7. The I/O port module 215, will in turn, determine (i.e. select) which light signal has the higher signal quality and outputs that signal via interface 400. In most cases, the signal quality of the two light paths presented to the I/O port module will be of the same signal quality and may have a relatively low optical loss of approximately seven decibels (7 dB) or less.
Referring now to FIGS. 2 and 7, each servo module 225 is configured to receive optical tap signals from one or more I/O port modules. Herein, servo module 225 i is configured to receive optical tap signals via link 500 from I/O port module 215 s. These optical tap signals provide feedback to indicate a percentage of the bridged light. signals and also allow for light to be injected under certain conditions. In response to receiving optical tap signals via link 500, the servo module 225 i provides mirror control signals over link 510 to the first optical switch core 240. The mirror control signals are routed via a unique communication path to an optical switch (e.g., a micro-machined mirror) and are associated with the port of the I/O port module 215 s through which the incoming light signal was routed. The mirror control signals are used for proper adjustment of the physical orientation of the mirror.
In the event that no optical power is presented to the I/O port module 215 s, a substitute light signal may be injected from the servo module 225 i via link 500. An alignment laser may be used as shown in FIG. 11 described below. This process of light substitution allows for connection establishment and verification when no input light is present to the I/O port module 215 s. The substitute light source can be within the same wavelength range (e.g. 1100 nanometers �nm�−1700 nm) as the allowed input light signal range. In one embodiment, the light source or method of injection would be chosen to not interfere with attached equipment's select operational wavelength range. Choosing a different wavelength source on the servo module and/or a wavelength specific splitter and/or filter on the I/O port module could do this particular embodiment.
As shown, each port of the I/O port module 2155 supports full-duplex communications. Thus, an incoming light signal 606 received over port 605 is routed to the splitter 620. The splitter 620 effectively performs a bridging operation by splitting the incoming light signal 606 into bridged light signals 625, which collectively have the same power level (energy) as the light signal 606. In one embodiment, when the splitter 620 is a 50/50 splitter, the bridged light signals 625 have equal power levels. However, it is contemplated that splitter 620 may produce bridged light signals 625 having disproportionate power levels.
Referring to FIG. 8, tap couplers 630 3 and 630 4 are configured to receive incoming light signal 650 and 655 via optical fiber ribbon links 430 and 440, respectively. The tap couplers 630 3 and 630 4 effectively separate the light signals 650 and 655 into corresponding pairs of light signals having disproportionate power levels (e.g., signals 661, 662 and 663, 664). Signals 662 and 664 having the lower power level are provided to the servo module 225 i and servo module 225 i+1 via links 500 and 520 for monitoring the power levels of the light signals 661 and 663, without the light signals 661 and 663 experiencing substantial signal degradation. The signals 662 and 664 may be light signals that undergo OE conversion at the I/O port module 215 s or at the servo modules 225 i and 225 i+1 as shown in FIG. 11. The tap couplers 630 3 and 630 4 are shown as 90/10 splitters; however, tap couplers 630 3 and 630 4 may be any selected ratio, including 50/50.
With respect to the primary optical path 800, a servo module 225 i is connected to both the source I/O port module 2155 and the first optical switch matrix (not shown) of the first optical switch core 240. In particular, the servo module 225 i controls the physical orientation of a mirror of the first optical switch matrix that corresponds to the source I/O port module 215 s. To establish and maintain the primary optical path 800 for the light signal, the servo module 225 i needs to communicate with other servo modules such as servo module 225 j. Thus, a servo control module (SCM) is implemented to support such communications, possibly through a time-slot switching arrangement.
As shown, the SCMs 236 1-236 2 are also duplicated so that each servo module 225 is connected to at least two SCMs 236 1-236 2. Thus, in the event that the SCM 236 1 fails, the primary optical path 800 remains intact because communications between the servo modules 225 i and 225 j are maintained via redundant SCM 237 1. The transfer is accomplished by temporarily halting the adjustment of (i.e. freezing) the mirrors inside the first optical switch core 240 while control is transferred from SCM 236 to SCM 237 1. The SCMs 236 1 and 237 1 associated with the first optical switch core 240 are in communication via a network control modules (NCMs) 238 1 and 238 2 for example.
To establish and maintain the redundant optical path 810 for the light signal, a SCM 236 2 may be implemented with a dedicated time-slot switching arrangement in order to support continuous communications between the servo module and another redundant servo module associated with the destination I/O port module. As shown, the SCM 236 2 is also duplicated so that each servo module 225 i+1 and 225 j+1 is connected to at least two SCMs 236 2 and 237 2. Thus, the redundant optical path 810 is maintained even when one of the SCMs 236 2 and 237 2 fails. The SCMs 236 2 and 237 2 associated with the second optical switch core 260 communicate via the first NCM 238 and the second NCM 238 2, respectively. The second NCM 238 2 is in communication with the first NCM 238 1 to allow all SCMs and servo modules to communicate for coordination of the primary optical path 800 and the redundant optical path 810.
The attached network equipment 1302 includes a network management controller 1320 and one or more I/O port cards 1321A-1321N (also referred to as line cards or herein previously as I/O port modules). Each of the one or more I/O port cards 1321A-1321N includes an optical�electrical-optical converter 1322A-1322N on its data input ports to couple to optical fibers of the data lines 1306A-1306N. The one or more optical-electrical-optical converters 1322A-1322N first convert the optical signals on the data lines 1306A-1306N into electrical signals and then convert the electrical signals into optical signals.
The one or more optical-elctrical-optical converters 1322A-1322N can be used for a number of reasons including to generate electrical signals to monitor the optical signal as well as to amplify (i.e. regenerate) low level incoming optical signals. In the conversion process, the one or more optical�electrical-optical converters 1322A-1322N provide information regarding the optical signals in electrical form which is tapped for monitoring purposes as the electrical signals 1323A-1323N. The electrical signals 1323A-1323N may include information from other sources of the respective port card 1315A-1315N that may be of relevance to the optical cross-connect switch. The one or more optical�electrical-optical converters 1322A-1322N and their electrical signals were originally used in the attached network equipment 1302 to facilitate its functionality and monitor its performance and not provide feedback to an optical cross-connect switch.
The attached network equipment 1402 that is illustrated coupled to the optical cross-connect switch 1400 is a WDM line terminal 1402. A WDM line terminal 1402 also includes a wave division multiplexer 1324 along with the one or more port cards 1421A-1421N with the optical�electrical-optical converters 1322A-1322N.
An optical-electrical-optical converter 1507 first converts an input optical signal into an electrical signal. The electrical signal can be tapped out to provide information regarding the input optical signal input into the O/E/O 1507 the O/E/O 1507 then converts the electrical signal into an output optical signal. The output optical signal from the O/E/O is similar to the input optical signal into the O/E/O in that the same data is being carried but the optical signal amplitude may be amplified, wavelength converted or otherwise improved in some way over that of the input optical signal. The O/E/O 1507 provides the conversion with little delay in the data carried by the optical signal.
The passive port cards 1603A-l603Z in the optical cross-connect 1600 provide control of the optical signals into and out of the optical switch fabric 1610. The smart port cards 1602A-1602M having the O/E/Os 1507 provide regeneration, performance monitoring, fault management and protection switching functions. By splitting the functionality of the port cards in this manner into the two tiered arrangement, replacement of faulty port cards can be less costly. The two tiered arrangement of I/O port cards also allows a system to be deployed with passive port cards initially with smart port cards being added later as needed. Also the smart port cards typically have different power and cooling requirements than the passive port cards, and may be located in separate shelves to provide additional cooling.
The smart port cards 1804A-1804N include an optical receiver 1817 (i.e. an optical to electrical converter (O/E) such as a photodiode) which is coupled to a pair of optical transmitters 1818A and 1818B (i.e. an electrical to optical converter (E/O) such as a semiconductor laser) in the input path 1811. Thus, in the input path 1811 of the smart port cards 1804A-1804N an optical-electrical-optical conversion (O/E/O)is performed. In the output path 1812, the smart port cards 1804A-1804N include an optical switch 1809 to select between two optical signals. The optical transmitters 1818A and 1818B generate the two parallel optical signals that are routed over two paths in the optical switch fabric such as optical paths 1815A and 1815A′. The optical switch 1809 selects between the two parallel optical signals to generate one as the output of the optical cross-connect 1800 on an output port. If the selected path should fail, the optical cross-connect switches to the other optical signal carried over the other optical signal path.
Referring to FIG. 19A, the optical cross-connect 1900A includes a first optical switch fabric 1910A and a second optical switch fabric 1910B and has one or more optical input ports 1901A-1901N and one or more optical output ports 1902A-1902N provided by the various port cards. The optical cross-connect 1900 also includes one or more smart port cards 1904A-1904N (generally referred to as 1904) and/or one or more smart port cards 1904A′-1904M′ (generally referred to as 1904′). The optical cross-connect 1900 can also include one or more test port/monitor cards 1905. The smart port cards 1904A-1904N provide an O/E/O 1907 in their input paths while the smart port cards 1904A′-1904M′ provide an O/E/O 1907′ in their output paths. The smart port cards 1904A-1904N and 1904A′-1904M′ each have an optical splitter 1908 and 1908′ respectively in their input paths. The smart port cards 1904A-1904N and 1904A′-1904M′ each have an optical switch 1909 and 1909′ respectively in their output paths. The O/E/Os 1907 and 1907′, optical switches 1909 and 1909′, and the optical splitters 1908 and 1908′ are optically coupled together within the smart port cards 1904A-1904N and 1904A′-1904M′ as shown and illustrated in FIGS. 19A and 19B. In either type of smart port cards 1904 or 1904′, the optical splitter 1908 or 1908′ splits the incoming optical signal into two split optical signals over two different optical paths one of which is coupled into the first optical switch fabric 1910A and the other which is coupled into the second optical switch fabric 1910B. In either type of smart port cards 1904 or 1904′, the optical switch 1909 and 1909′ selects an optical signal from between two optical signals over two differing optical signal paths one of which is received from the first optical switch fabric 19010A and the other of which is received from the second optical switch fabric 1910B. In this manner should an optical signal path in one of the two switch fabrics fail for any reason, the optical switch 1909 or 1909′ only need select the opposite signal path, For example consider the exemplary optical path 1915A in the optical switch fabric 1910A and the optical path 1915A′ in the optical switch fabric 19101B. Splitter 1908 in the smart port card 1904A splits an incoming optical signal into two split optical signals on optical paths 1921A and 1922A. The signal on the optical path 1921A is coupled into the first optical switch fabric 1910A and the signal on the optical path 1922A is coupled into the second optical switch fabric 1910B. The optical switches 1910A and 1910B switch these optical signals into the exemplary optical signal paths 1915A and 1915A′ respectively. The optical signal path 1915A in the optical switch fabric 1910A is coupled into the optical path 1923N which is coupled into the optical switch 1909′ of the smart port card 1904N. The optical signal path 1915A′ in the optical switch fabric 19101B is coupled into the optical path 1924N which is coupled into the optical switch 1909′ of the smart port card 1904N. In one case, the optical switch 1909′ of the smart port card 1904N selects the optical signals over the optical path 1915A so that the first optical switch fabric 1910A is acting as the active optical switch fabric. In another case, the optical switch 1909′ of the smart port card 1904N selects the optical signals over the optical path 1915A′ so that the second optical switch fabric 1910B is acting as the active optical switch fabric. If either optical switch fabric fails generating a gap, the other is automatically selected by the smart port cards to bridge the gap.
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