JP2005173043A - Multi-channel optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high-speed multi-channel optical module having a transmission rate of 10 Gbit / s or more per channel including an optical fiber.
SOLUTION: A flexible sheet 5 is used as a member for holding an optical fiber 7 and the optical element 25 and the IC 11 are absorbed by bending the flexible sheet 5 so as to absorb a processing error of components and the like. The distance between the IC 11 and the electric transmission line 12 is brought close to about several tens of μm, and the length of the wire connecting each of them is shortened.
[Selection] Figure 1

Description

  The present invention belongs to the field of optical communication, and particularly relates to a multi-channel optical module that transmits and / or receives a plurality of optical signals.

  In recent years, with the rapid spread of the Internet, the transmission capacity of a service provider's backbone optical network has increased rapidly. Therefore, in a station where a large-capacity router, an optical multiplex transmission apparatus, and the like are placed, there is an increasing demand for large-capacity and low-cost optical modules that connect each apparatus or between apparatuses. For such purposes, conventionally used optical modules are mainly multi-channel optical modules having a transmission rate per channel of several Mbit / s to several Gbit / s using multi-core ribbon fibers up to 12 cores. Has been widely used.

  In general, the structure of a parallel multi-channel optical module using a multi-core ribbon fiber includes a plurality of optical fibers for inputting / outputting optical signals, a receiving optical element for converting optical signals into electrical signals, or a module housing. Optical element for transmission that converts electric signal to optical signal, optical element mounting substrate on which optical element is mounted, transmission and reception ICs for amplifying electric signal, and electric signal transmission line for electric signal input / output Is included. The optical element and the IC, and the IC and the electric signal line are electrically connected by a wire.

  In particular, in a multi-channel optical module that transmits and receives optical signals, the electrical crosstalk between the transmitting side and the receiving side increases. Therefore, the transmitting optical element and the receiving optical element are mounted on separate optical element mounting substrates, and the IC is also configured. Separate for sending and receiving.

  In order to more effectively prevent spatial electrical crosstalk between transmission and reception, the transmitting optical element and the receiving optical element, and the transmitting IC and the receiving IC are separated from a standard multi-core fiber pitch of 250 μm. As one of the methods, there is a method in which an optical signal is exchanged with several channels at both ends of a multi-core ribbon fiber, and the middle few channels are not used. For example, an example shown in Japanese Patent Application Laid-Open No. 2002-311310 In a four-channel transmission / reception optical module using a 12-core ribbon fiber, an optical module that transmits and receives an optical signal through four channels at both ends and does not use the middle four channels is shown. However, in this method, the middle fiber is completely useless, increasing the optical fiber cost when actually laying. Therefore, in order to suppress electrical crosstalk between transmission and reception while using a multicore optical fiber without waste, it is necessary to expand the multicore fiber pitch from 250 μm on the side where the optical fiber in the module faces the optical element. There is.

  Further, as pointed out in Japanese Patent Application Laid-Open No. 2003-232944, a high-speed multichannel optical module has a large mounting pitch even if the same transmission or reception optical elements are used to suppress crosstalk between channels. It is desirable that the core ribbon fiber pitch be separated from 250 μm.

  Furthermore, in general, when an optical element is mounted on an optical element mounting substrate, the optical element is likely to deteriorate. Therefore, a method of improving the overall yield by separating and mounting the optical elements on the optical element mounting substrate several channels at a time is adopted. Furthermore, in order to increase the yield of multi-channel ICs, the ICs may be divided into ICs of several channels. Thus, from the viewpoint of improving the yield, it is better to use a plurality of optical element mounting substrates and ICs. ICs generally require a space such as a power supply line and a signal input / output line around the IC, and there are many methods for mounting a plurality of ICs at a pitch wider than 250 μm. Therefore, in such a case, the distance between the optical elements is separated from the multi-core ribbon fiber pitch of 250 μm, and a part of the optical fiber that is optically coupled with the optical element is also separated from the 250 μm.

  By the way, since the diameter of the core of the optical fiber is as thin as about 250 μm and is easily damaged such as buckling in the optical module manufacturing process, wiring is held by the optical fiber holding member except for necessary portions. In particular, in a multi-channel optical module that involves conversion of the optical fiber pitch, it is necessary to maintain the shape of the optical fiber pitch conversion unit. Therefore, the pitch conversion unit of the optical fiber is held by the optical fiber holding member.

  As an optical module of Conventional Example 1 that satisfies the above requirements, for example, there is one disclosed in JP-A-2002-311310. In this conventional example, two optical element mounting substrates on which optical elements are mounted are separately attached to a ceramic in which optical fibers are bent and held. Since it is necessary to align the optical element and the optical fiber with an accuracy of about several μm, for example, when the laser diode is aligned with the optical fiber, the following mounting method is adopted. That is, a current is passed through the laser diode to emit light, and while monitoring the light output from the fiber end opposite to the optical element, the mounting position of the optical element mounting substrate on which the laser diode is mounted is determined, and the optical block is Fix directly. The method of actually coupling the optical element by driving the optical element in this way is called an active alignment mounting method, and has a drawback that it takes time for optical coupling, and the adjustment cost is high, which increases the module cost.

  In general, as a method for reducing the manufacturing cost of an optical module, a passive alignment method for aligning optical fibers without driving an optical element is employed. As a conventional example 2, for example, Japanese Patent Laid-Open No. 8-292345 is disclosed. The described method is known. This is done by providing a mechanism for fitting and fixing an optical fiber such as a V-groove in advance on the optical element mounting substrate, and fitting the optical fiber into the V-groove and fixing it using an adhesive or the like. Is a way to take.

  FIG. 12 shows a part of the structure in the module housing as Conventional Example 3 in which Conventional Example 1 and Conventional Example 2 are simply combined. In the structure shown in FIG. 12, one end of the core wire of the optical fiber 7 is extended from the ceramic 35 and optical coupling is performed by fitting the core wire of the optical fiber 7 into the V grooves 16 on the plurality of optical element mounting substrates 10. Achieve.

  By the way, the ceramic 35, the optical element mounting substrate 10, the IC 11, the electric transmission line substrate 12, and components such as a module housing containing these have a processing error of several hundred μm or more at the time of manufacture. Accordingly, as shown in FIG. 13 as an example of the mounting method, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 are arranged close to each other, and then the optical fiber 7 and the V groove 16 held by the ceramic 35. When an attempt is made to fit each other, ΔX errors in the X direction and ΔY errors in the Y direction accumulate due to processing errors of the respective parts, which range from several hundred μm to several mm. It is impossible to make it fit. Although not shown in FIG. 13, there are errors in the Z-axis direction in addition to ΔX and ΔY, and angle errors in all directions to the same extent, which is an obstacle to the fitting of the optical fiber 7 and the V-groove 16. In order to solve these problems, in the current multi-channel optical module, as shown in FIG. 12, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 are arranged apart from each other without being arranged closely, and the parts are separated. By increasing the length of the wires 20a and 20b to be tied, the processing errors of all parts are absorbed by the wires 20a and 20b. The assembly order of the ceramic 35, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 may be any order, and the assembled state after assembly is the same as that shown in FIG.

  Of course, even when the optical element mounting substrate is directly fixed to the optical block as in Conventional Example 1, all processing errors of each component are absorbed by the wires connecting the components.

JP-A-8-292345 Japanese Patent Laid-Open No. 10-339818 JP 2001-324622 A JP 2002-311310 A JP 2003-232944 A Japanese Patent No. 3393101

  A wire connecting the optical element 25 and the IC 11, the IC 11 and the electric transmission line 19, or other electric transmission lines can be regarded as an inductance in terms of an electric equivalent circuit, and causes electromagnetic radiation and transmission loss in proportion to the length and frequency. Recently, the transmission speed per channel of the state-of-the-art multi-channel optical module has been required to be 10 Gbit / s or more. The optical element 25 and the IC 11, the IC 11 and the electric transmission line 19 are arranged close to several tens of μm, There is a need to shorten the wire to reduce the inductance due to the wire.

  Under such circumstances, the optical module shown in the conventional example 3 has the following practical problems. In Conventional Example 3, all the processing errors of each component are absorbed by the wire. For this purpose, the total length of the wires connecting the components must be several millimeters, and the influence of the increase in the inductance of the wire Therefore, the transmission rate per channel cannot be increased to 10 Gbit / s or more.

  Therefore, in a multi-channel optical module manufactured by including an optical fiber, the problems in realizing a high-speed multi-channel optical module with a transmission speed per channel of 10 Gbit / s or more are optical elements and ICs, and electrical transmission between ICs. The line and other electric transmission lines are arranged close to each other at several tens of μm or less, and the length of the wire connecting them is shortened to reduce the inductance due to the wire. It is an object of the present invention to provide a multi-channel optical module that can meet such a demand.

  According to the present invention, one module housing, an optical connector, a plurality of individual or array optical elements, a plurality of optical fibers for optical coupling to the optical elements, and a V-groove mechanism for fitting the optical fibers; In a multi-channel optical module including a plurality of optical element mounting substrates having a terrace for mounting the optical elements and a plurality of transmitting or receiving IC chips, at least a part of the optical fiber is flexible. The optical fiber core wire extends at one end facing the optical element of the optical sheet, and the optical fiber at the opposite end is connected to a multi-core optical connector. It is the most important feature. For the purpose of ensuring crosstalk between transmission and reception, crosstalk between channels, and securing a mounting space, the pitch between at least one optical fiber and another optical fiber may be separated from the multicore ribbon fiber pitch of 250 μm.

  As a flexible sheet for holding an optical fiber, the structure, material, Young's modulus, etc. are shown in, for example, Japanese Patent Application Laid-Open Nos. 2001-324622, 10-339818, and 3393101. In addition, a flexible plastic film having a low Young's modulus is known. However, a material such as paper or rubber may be used as long as the material has the same or lower flexibility. By bending the flexible sheet in the module, all the processing errors of the above-mentioned components are absorbed, and the optical element and the IC, the IC and the electric transmission line, and the electric transmission lines in other modules are several tens of μm. It can be placed close to:

  When optical fibers are divided into a plurality of groups according to individual optical element mounting substrates, the flexibility of connecting the groups of optical fibers to each group in order to make it possible to bend in different directions. You may provide a notch in at least one part of a sheet | seat. This makes it easier to fix the optical fiber to the optical element mounting substrate. Of course, the same effect can be obtained by changing a part of the flexible sheet to a material having a low Young's modulus instead of the notch.

  If the bending of the flexible sheet is transmitted to the optical fiber, the optical fiber may be bent and further bend. In order to avoid this, a part of the flexible sheet for wiring holding the optical fiber may be fixed to at least a part of the housing or at least a part of the base fixed to the housing.

  According to the present invention, it is possible to absorb all processing errors and the like of parts by bending the flexible sheet that holds the optical fiber by wiring. Accordingly, the distance between the optical element and the IC, the IC and the electric transmission line, or the electric transmission lines in the module can be made close to about several tens of μm, and the length of the wire connecting each of them can be shortened. it can. As described above, it is possible to realize a high-speed multi-channel optical module with a transmission rate per channel of 10 Gbit / s or more.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view of a multi-channel transmission / reception module for 4-channel transmission and 4-channel reception according to an embodiment of the present invention. A multi-core MT / MPO connector 3a and an adapter 1 are provided, and the adapter 1 is fixed to the module housing 4 with screws 2a, thereby forming a connector built-in module. The optical fiber 7 is held by the flexible sheet 5 in a curved line. The flexible sheet 5 is divided into two groups with the notch 15 as a boundary. The flexible sheet 5 is held by a screw 2b on a pedestal 6 attached to the module housing 4. The electromagnetic wave radiation preventing plate 8 is at least partially made of metal or a radio wave absorber. An optical element mounting substrate 10, an IC 11, and an electric signal line substrate 12 on which optical elements are mounted are mounted on a submount substrate 9. Outside the module housing are a power supply pin 13 for supplying power and an electrical signal pin 14 for inputting and outputting electrical signals.

  Here, in addition to the MT / MPO connector 3a and the adapter 1, any optical connector that connects multi-core fibers may be used. The MT / MPO connector 3a included in the adapter 1 may be either male or female. The MT / MPO connector 3a and the adapter 1 may be integrated.

  Generally, in a transmission / reception module, an optical element on the transmission side is driven with a current amplitude of several mA or more. On the other hand, the current amplitude inputted to the IC from the optical element on the receiving side is about several μA. As described above, since the difference in the amplitude level of the current flowing between the optical element and the IC is very large in transmission and reception, electrical crosstalk due to leakage of electromagnetic waves from the transmission side to the reception side is very large. In order to suppress the electrical crosstalk, the transmitting optical element and the receiving optical element are mounted on separate optical element mounting substrates 10. Furthermore, since the magnitude of the electrical crosstalk is almost inversely proportional to the distance, the optical fibers 7 are separated into two groups, and the distance between the two optical element mounting substrates 10 is separated.

  Furthermore, an electromagnetic wave radiation prevention plate 8 can be mounted in order to efficiently prevent crosstalk between transmission and reception. The electromagnetic wave radiation preventing plate 8 is at least partially made of metal or a radio wave absorber.

  When the module shown in the first embodiment is manufactured, the flexible sheet 5, the pedestal 6, the submount substrate 9, the optical element mounting substrate 10, the IC 11, and the electric signal line substrate 12 are generally provided in the module housing. After mounting, the MT / MPO connector 3 and the adapter 1 are generally attached to the module housing 4 using screws 2a. When the adapter 1, the screw 2a, and the MT / MPO connector 3 are attached, processing errors of the housing 4 and the flexible sheet 5, errors in the attachment position, and the like are added to the flexible sheet 5 as distortions. The portion of the optical fiber 7 that is not held by the flexible sheet 5 is added as strain, which may cause buckling and light loss. Therefore, before attaching the adapter 1, the screw 2a, and the MT / MPO connector 3, a method of fixing the flexible sheet 5 to the base 6 with the screw 2b is taken. Of course, the pedestal 6 may be integrated with the module housing 4.

  The optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 may be mounted separately on the same or a plurality of substrates and mounted on the module housing. The optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 may be directly mounted in the module housing. The electrical transmission line may be patterned directly in the module housing.

  FIG. 2 is an enlarged view of the mounting state on the submount substrate 9 in the first embodiment. Reference numeral 17 is a power line, and 19 is an electric signal line. The electric transmission line substrate 12 is bonded to the submount substrate 9 with solder. The chip capacitor 18 is bonded onto the electric transmission line substrate 12 with solder. The optical element mounting substrate 10 and the IC 11 are bonded on the submount substrate 9 using paste solder. The optical element mounting substrate 10, the IC 11, and the transmission line substrate 12 are mounted almost in contact. The bonding of the wire 20 may be performed at any timing after all or part of the optical element mounting substrate 10, the IC 11, and the transmission line substrate 12 are mounted on the submount substrate 9. Reference numeral 16 denotes a V-groove for fitting and fixing the optical fiber 7.

  As shown in FIG. 3, a submount substrate 9 with a pedestal 21 can also be used. Thus, after the optical fiber 7 is mounted in the V groove 16, the flexible sheet 5 is fixed to the base 21, so that the flexure of the flexible sheet 5 is held by the flexible sheet 5 of the optical fiber 7. Thus, it is possible to prevent the optical fiber 7 from being bent and light loss.

  FIG. 4 is an enlarged view of the optical element mounting substrate 10 and the IC 11 in the first embodiment. As the material for the optical element mounting substrate 10, a semiconductor material such as Si having excellent workability and excellent heat dissipation is used. A V-groove 16 is provided corresponding to the optical element 25 of each channel, and this has a function of guiding and fixing the optical fiber 7. Reference numeral 22 denotes a square groove. The optical element 25 is positioned at a predetermined position of the terrace 26 provided on the optical element mounting substrate 10 within a range of an error of about several μm by a passive alignment method using a high-precision mounting machine, and fixed by soldering. Is done. Here, in order to prevent crosstalk between channels, the optical elements 25 are mounted separately from the multi-core ribbon fiber pitch of 250 μm. Reference numeral 23 a denotes an optical element electrode pad provided on the optical element mounting substrate 10, and reference numeral 23 b denotes an optical element electrode pad attached to the optical element 25. After the optical element mounting substrate 10 and the IC 11 are mounted on the submount substrate 9 in contact with each other, the optical element electrode pad 23 and the IC electrode pad 24 are connected by bonding of the wire 20b.

  Furthermore, in order to prevent thermal interference and electrical crosstalk between the respective channels, the pitch of the optical elements 25 mounted on the same optical element mounting substrate 10 is also separated from the multi-core ribbon fiber pitch of 250 μm.

  FIG. 5 shows another embodiment of the optical element mounting substrate 10. The optical element mounting substrate 10 achieves optical coupling to the optical element 25 using a quartz or polymer waveguide, 27 is an optical waveguide cladding material, and 28 is an optical waveguide core material. Of course, it is also possible to make an optical multiplexer / demultiplexer structure by using an optical waveguide.

  FIG. 6 shows another embodiment of the optical element mounting substrate 10. An arrayed optical element 29 is mounted on the optical element mounting substrate 10. In this case, the light emitting surface and the incident surface of the arrayed optical element 29 are mounted so as to face downward in the drawing. The electrodes of the arrayed optical elements 29 face downward in FIG. 6, and are in contact with the element electrode pads 23a by a conductive material such as solder. The optical coupling with the optical fiber fixed to the V-groove 16 is performed by using reflection on the mirror surface 30.

  FIG. 7 shows an example of a part of the mounting process of the flexible sheet 5, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 in the first embodiment. The flexible sheet 5 may have any shape as long as it can be placed in the module housing 4. In FIG. 7, after the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 of the two groups 1 and 2 are arranged close to each other, one end of the optical fiber 7 held by the flexible sheet 5 is connected to the V groove. 16 shows a process of fitting and fixing to 16. When the two groups of parts 10, 11, and 12 are arranged close to each other, errors indicated by ΔX and ΔY are accumulated due to processing errors of the respective parts. One end of the fiber 7 can be fitted and fixed to the V-groove 16. That is, the errors ΔX and ΔY can be absorbed by the flexible sheet 5. Actually, errors in the Z-axis direction and the angle in each direction also occur, but this can also be absorbed by bending the flexible sheet 5.

  An example of the mounting state of the flexible sheet 5, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 assembled by the process shown in FIG. 7 is shown in FIG. As shown in FIG. 8, the optical fiber 7 achieves highly accurate optical coupling with the optical element while absorbing the error of the components in the groups 1 and 2 due to the flexible sheet 5 being bent, and the optical element. The mounting substrate 10, the IC 11, and the electric transmission line substrate 12 are arranged close to each other. The notch 15 makes it easier for the flexible sheets 5 of the groups 1 and 2 to bend in different directions, and makes it easier to fit the optical fiber 7 into the V-groove 16. In addition, by bonding a part of the flexible sheet 5 to the pedestal 6 using the adhesive 31a, the bending of the flexible sheet 5 is transmitted to the optical fiber 7 that is not held by the flexible sheet, and the light The fiber 7 is prevented from being bent or the like.

  Of course, the combination of the mounting order of the flexible sheet 5, the optical element mounting substrate 10, the IC 11, and the electric transmission line substrate 12 is arbitrary, and may be other than the mounting process shown in FIG. 7. In either case, the state after mounting is the same as in FIG.

  FIG. 9 shows a second embodiment provided with an electromagnetic wave radiation prevention case. In order to efficiently prevent electrical crosstalk, a part or all of the optical element mounting substrate 10, the IC 11, and the electrical transmission line substrate 12 may be surrounded by an electromagnetic wave radiation prevention case 32. The electromagnetic wave radiation prevention case 32 is at least partially made of metal or a radio wave absorber.

  FIG. 10 shows a third embodiment of the present invention. The MT / MPO connector 3 may be provided outside the module housing 4, and in this case, the state shown in FIG. The MT / MPO connector 3b may be either male or female. A multi-core ribbon fiber 34 extends from the flexible sheet 5 to the outside of the module housing 4. A notch 33 is provided in the module housing 4. The adhesive 31b fixes the multi-core ribbon fiber 34.

  The multi-channel optical module according to the present invention has a function of converting a multi-channel electrical signal into an optical signal, or vice versa. These multi-channel optical modules are housed in a router or a transmission device, and are used for high-speed information communication that connects within a few hundred meters within a station, in a building, between adjacent buildings, and the like. FIG. 11 shows an example of how the optical module is used in the first and third embodiments. Optical signals are exchanged between the optical modules via a multi-core ribbon fiber 34. The number of multi-core ribbon fibers 34 between the optical modules can be arbitrarily changed depending on the application. The electrical signal is input / output from 14 and processed in the router and the transmission device.

1 is a perspective view of an example of a multi-channel optical module according to the present invention. It is an expansion perspective view of an example of a substrate for mounting an optical element, an IC, and an electric transmission line substrate mounting portion. It is an expansion perspective view which shows an example of the board | substrate for optical element mounting, IC, and an electrical transmission line board | substrate mounting part. It is an enlarged view of an example of an optical element mounting substrate, (a) is a perspective view, (b) is sectional drawing of a V-groove direction. It is an enlarged view of the other example of an optical element mounting substrate, (a) is a perspective view, (b) is sectional drawing of a V-groove direction. It is an enlarged view of the other example of an optical element mounting substrate, (a) is a perspective view, (b) is sectional drawing of a V-groove direction. It is the top view which showed an example of the assembly method of the flexible sheet | seat which hold | maintained the optical fiber by wiring, an optical element mounting board | substrate, IC, and an electrical transmission line board | substrate. It is a figure which shows an example of the flexible sheet | seat which hold | maintained the optical fiber by wiring, an optical element mounting board | substrate, IC, and an electric transmission line board | substrate, (a) is a top view, (b) is sectional drawing of XZ plane. It is a perspective view which shows the other example of the multichannel optical module by this invention. It is a perspective view which shows the other example of the multichannel optical module by this invention. It is a figure which shows the utilization form of the multichannel optical module of this invention. It is a top view which shows the assembly method of the optical fiber in the module housing in a prior art example, an optical element, IC, and an electric transmission line board | substrate. It is a top view which shows the mounting aspect of the optical fiber in the module housing in a prior art example, an optical element, IC, and an electrical transmission line board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adapter 2 Screw 3 Multicore MT / MPO connector 4 Module housing 5 Flexible sheet 6 Base 7 Optical fiber 8 Electromagnetic wave radiation prevention board 9 Submount board 10 Optical element mounting board 11 IC
12 Electrical Transmission Line Board 13 Power Supply Pin 14 Electrical Signal Pin 15 Notch 16 V Groove 17 Power Supply Line 18 Chip Capacitor 19 Electrical Signal Line 20 Wire 21 Base 22 Square Groove 23 Optical Element Electrode Pad 24 IC Electrode Pad 25 Optical Element 26 Terrace 27 Optical waveguide cladding material 28 Optical waveguide core material 29 Array optical element 30 Mirror surface 31 Adhesive 32 Electromagnetic wave radiation prevention case 33 Notch 34 Multi-core ribbon fiber 35 Ceramic

Claims (3)

A module housing, a multi-core optical connector, a plurality of individual optical elements or array optical elements, a plurality of optical fibers for optical coupling to the optical elements, and a V-groove for positioning the plurality of optical fibers In a multi-channel optical module comprising a plurality of optical element mounting substrates having a mechanism and a terrace for mounting the optical elements, and a plurality of transmitting and / or receiving IC chips,
At least a part of the plurality of optical fibers is held by a flexible sheet, and one end of the plurality of optical fibers extending from one end of the flexible sheet faces the optical element, and the plurality of light beams The multi-channel optical module, wherein the other end of the fiber is connected to the multi-core optical connector.   2. The multi-channel optical module according to claim 1, wherein the flexible sheet has a notch, and the plurality of optical fibers held by the flexible sheet with the notch as a boundary are a plurality of groups. A multi-channel optical module characterized by being divided into   3. The multi-channel optical module according to claim 1, wherein at least a part of the flexible sheet is fixed to the module housing or a base fixed to the module housing.

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