JP2011204457A - Cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable capable of controlling the difference in the transmission time of each channel.SOLUTION: The cable 11, which transmits multi-channelled signals is provided with a plurality of optical fibers 21 installed for each channel, circuit boards 13A, 13B installed at both ends of the optical fibers 21; a plurality of terminal parts 31 which are installed for every channel and are arranged in the circuit boards 13A, 13B; and conduction patterns 41 which are installed in the circuit boards 13A, 13B and conduct between each optical fiber 21 and each terminal part 31. The conduction pattern 41 in respective circuit boards 13A, 13B has a different length for each channel, and the total length of line of the conduction pattern 41 connected at both ends of the respective optical fibers 21 has identical length for each channel.

Description

  The present invention relates to a cable for transmitting multi-channel signals in parallel.

  An electrical connector that can be attached to and removed from the outside as a cable that connects boards between electronic devices such as computers, information processing, displays, printers, between boards and built-in devices, or between each electronic device, and optical signals There is known an optical transmission means capable of transmitting the light and an optical element for photoelectric conversion (for example, see Patent Document 1).

  The optical element is a light emitting element that is modulated by an electrical signal connected at the conductive portion of the electrical connector section, and a light receiving device that converts the optical signal transmitted by the optical transmission means into an electrical signal for connection to the conductive section of the electrical connector section. At least one of the elements is integrated and the optical element is aligned and fixed so as to be optically coupled to the optical transmission means.

JP 2001-42170 A

  In the cable as described above, in order to realize large-capacity transmission, a configuration is adopted in which signals are multi-channeled and transmitted in parallel. In such a cable, the circuit boards provided at both ends of the cable have a plurality of terminal portions corresponding to each channel on the electrical interface side connected to the receptacle or the like, and a small photoelectric device on the connection side of the optical fiber. A conversion unit is included, and each terminal unit and the photoelectric conversion unit are electrically connected by a circuit pattern.

  The width dimension of the electrical interface side on which the terminal portions are arranged is larger than that of the photoelectric conversion unit that is small and has a small width dimension. For this reason, there is a difference in the distance from the photoelectric conversion unit for each terminal unit, and there is a difference in the length of a plurality of circuit patterns that conduct the terminal unit and the photoelectric conversion unit. A transmission time difference (skew) occurs.

  The objective of this invention is providing the cable which can suppress the transmission time difference of each channel as much as possible.

The cable of the present invention capable of solving the above problems is a cable for transmitting a multi-channel signal,
A plurality of signal lines provided for each channel;
Connecting members provided at both ends of the signal line;
A plurality of terminal portions provided for each channel and arranged in a row on the connection member;
A conductive path provided in the connecting member and electrically connecting each signal line and each terminal portion;
The conduction path in each of the connection members has a different length for each channel,
The total line length of the conducting paths connected to both ends of each signal line has the same length for each channel.

  In the cable of the present invention, the signal line includes an optical fiber, the connection member is provided with a photoelectric converter, and the optical fiber and the conduction path are connected to the photoelectric converter. Is preferred.

In the cable of the present invention, each of the connection members is arranged in point symmetry with respect to the center of the cable in the arrangement of the conduction paths.
It is preferable that each of the connection members is formed so as to be gradually longer from one end side to the other end side of the terminal portion array in each connection member.

  In the cable of the present invention, it is preferable that the conduction path is formed in a linear shape.

According to the cable of the present invention, the conductive path in each connection member has a different length for each channel, but the total line length of the conductive paths connected to both ends of each signal line is the same length for each channel. It is said. In other words, the transmission path of each channel through which signals are transmitted between the terminal sections is adjusted so that the path length is the same, so the transmission time difference when signals are multi-channeled and transmitted in parallel is reduced. It can be suppressed as much as possible.
Moreover, since it is not necessary to provide a skew adjustment part in a connection member, the external shape of a connection member can be made small and size reduction of the terminal part of a cable can be achieved.

It is a schematic block diagram which shows the structure of the cable which concerns on embodiment of this invention. It is a schematic wiring diagram which shows the transmission path | route of the cable which concerns on embodiment of this invention. It is a schematic block diagram which shows the reference example of the active optical cable used for transmission of the signal made multi-channel.

Hereinafter, an example of an embodiment of a cable according to the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the cable 11 includes a multi-core optical cable portion 12 and circuit boards (connection members) 13A and 13B provided at both ends of the multi-core optical cable portion 12. It has the form of an active optical cable that transmits a channelized signal.

  The multi-core optical cable unit 12 is a bundle of a plurality of optical fibers 21 provided for each channel, and these optical fibers 21 function as signal lines. The optical fiber 21 is obtained by coating a glass fiber composed of a core and a clad with a resin. The multi-core optical cable portion 12 may include a metal conductive line used as a signal line or a power line.

  The circuit boards 13A and 13B are made of, for example, a flexible printed circuit board (FPC), and a circuit pattern is formed on the surface of the base material. Each circuit board 13A, 13B has a plurality of terminal portions 31 provided for each channel, and these terminal portions 31 are arranged on one side of the circuit boards 13A, 13B. One side where these terminal portions 31 are provided is configured as electrical interface portions 32A and 32B connected to a receptacle (not shown) or the like.

  The circuit boards 13A and 13B are mounted with photoelectric converters 34A and 34B on the other side, and the optical fibers 21 of the multi-core optical cable section 12 are connected to the photoelectric converters 34A and 34B. Has been. The photoelectric converters 34A and 34B are arranged on one side of the circuit boards 13A and 13B (the lower side in the circuit board 13A and the upper side in the circuit board 13B) in each of the circuit boards 13A and 13B.

  The photoelectric converters 34A and 34B have a structure in which the photoelectric conversion elements are conductively connected by bumps to a ferrule having a structure in which a plurality of electrodes are integrally formed, for example. By connecting the optical fiber 21 to the ferrules of the photoelectric converters 34A and 34B, optical signals can be transmitted and received between the optical fiber 21 and the photoelectric conversion elements of the photoelectric converters 34A and 34B. In the photoelectric converter 34A on the transmission side, a VCSEL (Vertical Cavity Surface Emitting Laser) for converting an electrical signal into an optical signal is used as a photoelectric conversion element. In the photoelectric converter 34B on the receiving side, a PD (Photodiode) for converting an optical signal into an electrical signal is used as a photoelectric conversion element. The transmitting-side photoelectric converter 34A includes a driver IC that drives the VCSEL, and the receiving-side photoelectric converter 34B includes a transimpedance amplifier (TIA) that amplifies a signal from the PD.

  The circuit boards 13A and 13B are provided with a conduction pattern (conduction path) 41 for each channel. These conductive patterns 41 are formed of circuit patterns formed on the circuit boards 13A and 13B, and are each formed in a linear shape. And by these conduction patterns 41, the terminal portions 31 of the electrical interface portions 32A and 32B and the photoelectric converters 34A and 34B to which the optical fiber 21 is connected are conductively connected.

In each circuit board 13A, 13B, each conductive pattern 41 gradually increases in length from one side to the other side in the vertical direction in the figure where the photoelectric converters 34A, 34B are arranged. Is formed.
That is, in the circuit board 13A, each conductive pattern 41 is formed so that the length gradually increases from one end side (lower side) to the other end side (upper side) of the arrangement of the terminal portions 31. Each conductive pattern 41 is formed such that its length gradually increases from one end side (upper side) to the other end side (lower side) of the arrangement of the terminal portions 31. As a result, each conductive pattern 41 has a different length for each channel in each of the circuit boards 13A and 13B, that is, an unequal length.

  Further, in each of the circuit boards 13A and 13B, the arrangement of the photoelectric converters 34 and the arrangement of the conductive patterns 41 having different lengths are reversed. That is, in each circuit board 13, the conductive pattern 41 is arranged at a point-symmetrical position with respect to the cable center O. Accordingly, in the cable 11 described above, the total line length of the conductive pattern 41 connected to both ends of each optical fiber 21 via the photoelectric converter 34 is configured to have the same length for each channel. Yes.

Specifically, the length of the conductive pattern 41 on one circuit board 13A is L1a, L1b, L1c, L1d,..., L1n in order from the shortest, and the length of the conductive pattern 41 on the other circuit board 13B is In the case of L2a, L2b, L2c, L2d,..., L2n from the longest side, the total length of the conductive pattern 41 connected through the optical fiber 21 for each channel has a relationship as shown in the following equation.
L1a + L2a = L1b + L2b = L1c + L2c = L1d + L2d = ... = L1n + L2n

  In the cable 11 having the above-described configuration, an electric signal input from each terminal portion 31 of one circuit board 13A is transmitted to the photoelectric converter 34A through each conduction pattern 41 of the circuit board 13A. The electrical signal is converted into an optical signal by 34 A, and the optical signal is input to the optical fiber 21. The optical signal input to the optical fiber 21 is converted into an electrical signal by the photoelectric converter 34B of the other circuit board 13B, and this electrical signal is output from each terminal portion 31 through each conduction pattern 41 of the circuit board 13B. Is done. As a result, according to the cable 11, signals can be multi-channeled and transmitted in parallel by the optical fiber 21, and large capacity transmission is possible.

  In this way, when signals are multi-channeled and transmitted in parallel, it is necessary to suppress the transmission time difference (skew) as much as possible in each channel. The suppression of the transmission time difference becomes particularly strict as the transmission rate becomes higher. For example, in the InfiniBand specification, in the case of a QDR (Quad Data Rate) signal (transmission rate 10 Gbps), it is required to suppress the transmission time difference to 125 ps or less.

  In an active optical cable that transmits signals using multiple channels, the width of the electrical interface section on which the terminal sections are arranged is larger than that of a small-sized photoelectric conversion section having a small width dimension. For this reason, the distance between each terminal unit and the photoelectric conversion unit differs for each channel, and when these terminal units and the photoelectric conversion unit are connected by a linear conductive pattern, one terminal unit to the other terminal unit The length of the wiring path up to this becomes unequal for each channel, and the transmission time difference cannot be suppressed.

  Here, as in the case of the cable 50 shown in FIG. 3, in order to make the conductive pattern 51 have the same length by the respective wiring boards 53A and 53B, the terminal portion 31 is relatively close to the photoelectric conversion portions 34A and 34B. It is conceivable to adjust the length of the conductive pattern 51 to be equal to that of the other conductive pattern 51 by providing a skew adjusting portion S in which the line is bent in the conductive pattern 51 to be connected.

However, in this case, the transmission loss is increased by providing the skew adjusting portion S in the conductive pattern 51, the impedance is changed with respect to the other conductive patterns 51, and the signal quality is deteriorated due to the electric reflection.
Further, when the skew adjusting portion S is provided in the conductive pattern 51, an arrangement space for the skew adjusting portion S is required, which leads to an increase in the size of the circuit boards 53A and 53B.

  According to the cable 11 of the present embodiment, the conductive patterns 41 in the respective circuit boards 13A and 13B are formed in different lengths for each channel, but the conductive patterns 41 connected to both ends of the respective optical fibers 21 The total line length is the same for each channel. That is, the transmission path between the terminal sections 31 through which signals are transmitted between the electrical interface sections 32A and 32B of the cable 11 is adjusted so that the path length is the same length. The transmission time difference when parallel transmission is performed can be suppressed as much as possible.

Further, since it is not necessary to provide the skew adjusting portion S on the circuit boards 13A and 13B, the outer shape of the circuit boards 13A and 13B can be reduced, and the terminal portion of the cable 11 can be reduced in size. For example, the dimension in the wiring direction of the circuit boards 13A and 13B can be reduced by about 10 mm as compared with the cable 50 of FIG.
Further, the conductive patterns 41 of the circuit boards 13A and 13B are arranged symmetrically with respect to each other with respect to the cable center O. In each of the circuit boards 13A and 13B, from one end side to the other end side of the arrangement of the conductive patterns 41. Since the length of the conductive pattern 41 is gradually increased, it is possible to facilitate the design of circuit patterns and the ease of skew adjustment on the circuit boards 13A and 13B.

  In addition, since the path length is adjusted while the conductive pattern 41 is kept in a linear shape without forming a bent portion as a skew adjusting portion in the conductive pattern 41, signal quality is deteriorated by bending the conductive pattern 41. It is possible to suppress the transmission time difference without causing the.

In the above-described embodiment, the active optical cable in which the circuit boards 13A and 13B are connected to each other by the plurality of optical fibers 21 is described as an example. However, the circuit boards 13A and 13B are connected to each other by a plurality of electric wires. A cable for transmitting electrical signals from the side to the output side in multiple channels may be used. In this case as well, the wiring path length in each channel can be made the same to suppress the transmission time difference.
Further, the circuit board 13 is not limited to a flexible printed board but may be a hard printed board or the like.

11: Cable, 21: Optical fiber (signal line), 13: Circuit board, 31: Terminal part, 41: Conducting path (conducting pattern), 34: Photoelectric converter, O: Cable center

Claims (4)

A cable for transmitting multi-channel signals,
A plurality of signal lines provided for each channel;
Connecting members provided at both ends of the signal line;
A plurality of terminal portions provided for each channel and arranged in a row on the connection member;
A conductive path provided in the connecting member and electrically connecting each signal line and each terminal portion;
The conduction path in each of the connection members has a different length for each channel,
A cable characterized in that a total line length of the conduction paths connected to both ends of each signal line has the same length for each channel. The cable according to claim 1,
The signal line includes an optical fiber, the connection member is provided with a photoelectric converter, and the optical fiber and the conducting path are connected to the photoelectric converter. The cable according to claim 1 or 2,
Each of the connection members is arranged such that the arrangement of the conduction paths is point-symmetric with respect to the center of the cable,
The cable is characterized in that the conduction path is formed so as to be gradually longer from one end side to the other end side of the arrangement of the terminal portions in each of the connection members. The cable according to any one of claims 1 to 3,
The cable is characterized in that the conduction path is formed in a straight line shape.

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