JPH0750634A - Optical transmitter - Google Patents

Abstract

PURPOSE:To define the maximum transmission speed by which a photoelectric conversion element is possible to operate as the transmission speed of a signal to be transmitted also when a photoelectric conversion element for clock signal and the photoelectric conversion element for signal to be transmitted which synchronizes with the clock signal are made to have the same constitution. CONSTITUTION:In a device where a clock signal and a signal to be transmitted synchronizing with this clock signal are transmitted as optical signals, a transmitter 11 is provided with a frequency divider circuit 12 frequency dividing a clock signal 600 as an electric signal to two and imparting the two frequency divided clock signal 610 to a photoelectric conversion element 13. In a receiver 16, a multiplication circuit 15 performing two multiplication for the clock signal 120 converted into the electric signal is provided. By synchronizing with the two multiplied clock signal 730, signals to be transmitted 701 to 709 converted into electric signals are latched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission apparatus for transmitting a clock signal and a signal to be transmitted synchronized with the clock signal using light, and more particularly to a clock signal transmitted by light. The present invention relates to an optical transmission device in which the frequency is divided into 1/2.

[0002]

2. Description of the Related Art As shown in FIG. 6, a widely used optical transmission apparatus, which has little influence of ambient noise and is capable of high-speed data transmission, includes a transmission apparatus 40, an optical fiber cable 44, and It is configured by the receiving device 49.

The transmitter 40 is provided with a connector 41 for electrical connection with the outside, and photoelectric conversion elements 42, 43 for converting an electric signal guided through the connector 41 into an optical signal. , 47 are provided.
Further, in the configuration of the photoelectric conversion element, the element 42 for the clock signal 600, the element 43 for the data signals 601 to 608, and the element 47 for the control signal 609 are all the same.

On the other hand, the receiving device 49 is provided with photoelectric conversion elements 45, 46 and 48 for converting an optical signal guided through the optical fiber cable 44 into an electric signal. Further, the converted data signal 7 is synchronized with the rising edge of the clock signal 700 converted into the electric signal.
01 to 708 and control signal 709 are each latched 9
Two D flip-flops 50 are provided. Also,
A connector 51 for outputting the clock signal 700 and the signal latched by the D flip-flop 50 to the outside is provided.

Regarding the photoelectric conversion elements 45, 46 and 48, the element 45 for the clock signal 700 is constituted by an AC coupling amplifier in order to enable the operation in a high frequency band. Also, the data signals 701 to 7
08 and the photoelectric conversion element 46 for the control signal 709,
The 48 is configured by a DC coupling amplifier in order to enable operation in a wide frequency band. This configuration is referred to as Prior Art 1.

Further, as another structure, the conventional technique 1 is used.
In the above configuration, there is a configuration in which all of the photoelectric conversion elements 45, 46, and 48 are DC coupling amplifiers that can operate in a high frequency band and can operate in a wide frequency band. And).

[0007]

As a general characteristic of the above configuration, when the data transmission rate is represented by f [bps], the clock signal transmission rate is 2 × f [b].
ps] is required. Since the other signal is latched by the rising edge of the clock signal, the phase of the clock signal needs to be aligned with the phase of the other signal.

Therefore, in order to realize a device in which the transmission rate of each channel of the data signal is f [bps], at least 2 photoelectric conversion elements 45 for the clock signal 700 are used.
It is necessary to use a high-speed element capable of transmitting xf [bps]. Further, when the transmission speed f [bps] is high, it is necessary to suppress the variation in the transfer characteristics of the photoelectric conversion elements 45, 46, 48, and to suppress the input frequency fluctuation of the transfer characteristics, the ambient temperature fluctuation, the power supply voltage fluctuation, and the like. Need to reduce.

Further, the data signals 701 to 708 and the control signal 709 are generally in a protocol having a DC component, and therefore these signals 701 to 709.
The photoelectric conversion elements 46 and 48 for use must be operable in a wide frequency band.

Therefore, in the prior art 1, since the photoelectric conversion element 45 for the clock signal 700 and the photoelectric conversion elements 46, 48 for the data signals 701 to 708 and the control signal 709 have different circuit configurations, It is difficult to make the propagation time of the photoelectric conversion element 45 and the propagation times of the photoelectric conversion elements 46 and 48 coincide with each other. Further, between the photoelectric conversion element 45 and the photoelectric conversion elements 46 and 48, there arises a problem that variations in propagation time with respect to the input frequency, variations with changes in ambient temperature, variations with changes in power supply voltage, etc. do not match.

This will be described with reference to FIG.

As shown in FIG. 1A, the phase of the clock signal 600 guided to the connector 41 and the data signal 60
1 to 608 and the phase of the control signal 609 are the setup time ts1 and the hold time t with respect to the rising edge.
There is a relationship in which the margin of h1 is sufficiently secured. Also,
The mutual phase relationships in the optical fiber cable 44 are as shown in FIG. In the phase relationship between the signals 700 to 709 converted into electric signals in the receiving device 49, the margin of the setup time ts2 is secured even if the margin of the hold time th2 is secured, as shown in FIG. It becomes a relationship that is not done.

Therefore, the data signals 711 to 718 and the control signal 719, which are the outputs of the D flip-flop 50 output to the outside through the connector 51, have no margin for the setup time ts2, and are not read by the D flip-flop 50. Certainty is not guaranteed. That is, as shown in FIG. 7D, for example, the data signal 708 originally has to be at the H level as shown by the dotted line H718, but as shown by L718, L
It becomes a level and a transmission error occurs.

Therefore, in the prior art 1, even if the data transmission speed of each channel is within the transmission speed range of the photoelectric conversion elements 46 and 48, it is difficult to achieve a high speed exceeding, for example, 10 Mbps. Was there.

On the other hand, in the prior art 2, the photoelectric conversion element 4
5, 46 and 48 have the same configuration in all,
In these elements 45, 46 and 48, the variation of the propagation time with respect to the input frequency, the variation with respect to the change of the ambient temperature, the variation with respect to the change of the power supply voltage and the like have a substantially matched relationship. Therefore, even if the transmission speed is increased, a margin is secured for the setup time and the hold time in the D flip-flop 50, and no error occurs in data transmission.

However, for that purpose, it is necessary that all of the photoelectric conversion elements 45, 46, and 48 be configured to be capable of operating in a high frequency band and capable of operating in a wide frequency band. That is, in the case of a high-speed transmission device having a maximum data transmission rate of, for example, more than 10 Mbps, all the photoelectric conversion elements 45, 46, and 48 are elements capable of transmission at a rate twice the maximum transmission rate. There is a need to. Therefore, there has been a problem that the photoelectric conversion element becomes expensive.

The present invention was devised to solve the above problems, and its object is to provide a photoelectric conversion element for a clock signal and a photoelectric conversion element for a transmitted signal synchronized with the clock signal. An object of the present invention is to provide an optical transmission device capable of setting the maximum transmission rate at which the photoelectric conversion element can operate to the transmission rate of the transmitted signal even when the same configuration is used.

[0018]

In order to solve the above-mentioned problems, the optical transmission apparatus of the present invention is configured such that a clock signal and a signal to be transmitted synchronized with the clock signal are introduced as electrical signals, and these two types are introduced. A transmitter that converts a signal into an optical signal by using a photoelectric conversion element, and an optical signal from the transmitter that is guided through an optical fiber cable is converted into an electrical signal by using a photoelectric conversion element, and the signal is converted. It is applied to an optical transmission device comprising a receiving device that latches a converted transmitted signal in synchronization with a clock signal, and the transmitting device includes
The clock signal as an electric signal is divided by 2 and
A frequency dividing circuit for providing the frequency-divided clock signal to the photoelectric conversion element is provided, and the receiving device is provided with a multiplying circuit for multiplying the clock signal converted into the electric signal by two. The transmitted signal converted into an electric signal is latched in synchronization with the doubled clock signal.

[0019]

Since the level of the transmitted signal does not change in one cycle of the clock signal, the maximum value of the frequency of the transmitted signal is 1/2 of the clock signal (hereinafter, the frequency of the transmitted signal is the clock. The case where the signal frequency is ½) will be described).

However, in the transmitting device, since the clock signal is divided into 1/2 by the frequency dividing circuit, when the clock signal and the transmitted signal are viewed from the photoelectric conversion element, the ratio of their frequencies is It is one-to-one. That is, the maximum operable frequency required for the photoelectric conversion element is the same in the clock signal and the transmitted signal.

Therefore, the frequency of the optical signal guided to the receiving device via the optical fiber cable is also equal in both the clock signal and the transmitted signal. That is, the maximum operable frequency required for the photoelectric conversion element of the receiving device is the same for both the clock signal and the transmitted signal.

As a result, in the receiving device, the clock signal and the transmitted signal converted into an electric signal by the photoelectric conversion element become signals having the same frequency. And
The clock signal is doubled by the multiplication circuit, and this doubled clock signal becomes a signal corresponding to the clock signal given to the transmitter as an electric signal. Therefore, in the receiving device, the transmitted signal converted into the electric signal by the photoelectric conversion element is latched in synchronization with the doubled clock signal.

[0023]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the electrical construction of an embodiment of the optical transmission apparatus according to the present invention. The blocks having the same construction as the prior art shown in FIG. 6 have the same reference numerals. Granted.

The optical transmission apparatus of this embodiment is roughly classified into a transmission apparatus 11 for converting a clock signal given as an electric signal and a transmitted signal synchronized with this clock signal into an optical signal, and an optical apparatus for transmitting the optical signal. The three blocks of the fiber cable 44 and the receiving device 16 for converting the optical signal guided through the optical fiber cable 44 into an electric signal and latching the converted transmitted signal in synchronization with the converted clock signal It is configured.

A clock signal 600, data signals 601 to 608, and a control signal 609 are led to the connector 41 provided in the transmitter 11 as electrical signals. Of these signals, the data signals 601 to 608
Is a transmitted signal synchronized with the clock signal 600,
It is a signal indicating 8-bit parallel data. The control signal 609 is a transmitted signal synchronized with the clock signal 600 and is a signal used for control.

Further, the frequency dividing circuit 12 to which the clock signal 600 is guided is, as shown in FIG. 2, a frequency dividing circuit using a D flip-flop, which maintains the phase of the clock signal 600. It is a block that divides the frequency in half, and sends the divided clock signal 610 to the photoelectric conversion element 13. Further, each of the data signals 601 to 608 is guided to the corresponding photoelectric conversion element 43, and the control signal 609 is guided to the photoelectric conversion element 47.

Then, the photoelectric conversion element 13 for the clock signal divided into 1/2 and the data signals 601 to 608.
And the photoelectric conversion element 47 for the control signal 609 are a block for converting the guided electric signal into an optical signal and sending the converted optical signal to the optical fiber cable 44. . In addition, the photoelectric conversion element 1
3, 43, 47 all have the same configuration,
A DC coupled amplifier is used.

Further, the photoelectric conversion elements 14, 46, 48 to which the optical signal is guided via the optical fiber cable 44 are blocks for converting the optical signal into an electric signal, and all the photoelectric conversion elements 14, 46, 48. Have the same configuration and use a DC coupling amplifier.

The frequency multiplication circuit 15 is composed of a PLL circuit, and the frequency of the frequency multiplication circuit 2 is 2 without impairing the signal phase.
It is a block that is multiplied. The clock signal 720 converted into an electric signal by the photoelectric conversion element 14 is guided to the multiplication circuit 15. In addition, the multiplication circuit 15
Sends the doubled clock signal 730 to the clock input of the D flip-flop 50 and the connector 51.

Further, each of the data signals 701 to 708 converted into electric signals by the photoelectric conversion element 46 and the control signal 709 converted into electric signals by the photoelectric conversion element 48 respectively receives the data input of the corresponding D flip-flop 50. Have been sent to.

The D flip-flop 50 is a multiplication circuit 15
It is a block that latches the data signals 701 to 708 and the control signal 709, which are the transmitted signals converted into electric signals, in synchronization with the doubled clock signal 730 output from the. The clock signal 730 and the output of the D flip-flop 50 are led to a connector 51 provided for electrical connection with the outside.

The terminal 411 of the connector 41 and the terminal 511 of the connector 51 are power supply terminals.

FIG. 3 is a timing chart showing the timing of main signals according to an embodiment of the present invention. The operation of one embodiment of the present invention will be described below with reference to FIG.

A clock signal 600, data signals 601-608 and a control signal 609 are led to the connector 41. At this time, the phase relationship between these signals is shown in FIG.
As shown in (a), the setup time ts3 and the hold time th3 are sufficiently secured with respect to the rising edge of the clock signal 600.

The clock signal 600 is divided into two by the frequency dividing circuit 12, but the phase does not change in this frequency division. Further, the photoelectric conversion element 13 for the divided clock signal 610 has the same configuration as the photoelectric conversion element 43 for the data signals 601 to 608 and the photoelectric conversion element 47 for the control signal 609. Even in the conversion of, the mutual phase relationship does not change.

Therefore, the relationship between the signals in the optical fiber cable 44 is that the clock signal, which is an optical signal, is 80
0, data signals 801 to 808 and control signals 809 are optical signals, as shown in FIG. 3B, the data signals 801 to 808 and the control signal 809 are shown.
Is the rising edge of the clock signal 800
Both the setup time ts4 and the hold time th4 have a sufficiently secured phase relationship.

Then, these optical signals 800 to 809
Is converted into electric signals 720, 701 to 709 by the photoelectric conversion elements 14, 46 and 48 having the same configuration,
As shown in FIG. 3 (c), the mutual relationship is that the setup time t is relative to the rising edge of the clock signal 720.
s5 and hold time th5 are secured.

Further, the clock signal 720 is supplied to the multiplication circuit 15
Is multiplied by 2, the multiplication at this time is multiplication that does not change the phase. Therefore, the relationship between the clock signal 730 sent from the multiplication circuit 15 and the data signals 701 to 708 and the control signal 709 is substantially the same as the relationship with each signal guided to the connector 41. That is, the data signals 701 to 708 and the control signal 709 have the setup time ts6 and the hold time th6 with respect to the rising edge of the clock signal 730.
Is a sufficiently secured signal.

Therefore, the reading in synchronization with the rising edge of the clock signal 730 in the D flip-flop 50 becomes the reading in which the operation is guaranteed, and the connector 51 is provided with the signals 601 to 601 given to the connector 41.
Signals 731 to 739 equal to 609 will be transmitted.

FIG. 4 is a circuit diagram showing the electrical connection of the second embodiment of the multiplication circuit 15, and in this embodiment,
The delay element 31 is used to perform multiplication.

Therefore, as shown in FIG. 5, a clock signal (1/1 is converted into an optical signal and converted into an electric signal again.
The clock signal divided by 2) 720 is represented by t1 and

[0043]

## EQU1 ## t1 = t2 + t3 + t4 + t5

[0044]

## EQU00002 ## If t2 = t3 = t4 = t5, the output out1 has the delay time = 0 and the output out2.
Is delay time = t2, output out3 is delay time = t2 + t
3, the output out4 is set so that the delay time = t2 + t3 + t4.

Since the delay time of the delay element 31 is set as above, the clock signal output from the EXOR gate 32 is a signal obtained by doubling the clock signal 720 without changing its phase. This signal is the same as the clock signal 730 when the multiplication circuit 15 is configured by a PLL circuit. Therefore, this clock signal 73
The operation based on 0 is the same as the operation already described.

As described above, in the second embodiment, since the multiplier circuit 15 has the structure using the delay element 31, the circuit structure is simple. Therefore, when the frequency of the clock signal 600 is determined in advance, it is possible to simplify the configuration of the multiplication circuit 15.

The present invention is not limited to the above embodiment,
The transmitted signal has been described as an 8-bit data signal and a 1-bit control signal, but other signal configurations may be, for example, a 1-bit serial signal or a 16-bit parallel data signal. It is possible.

[0048]

The optical transmission apparatus of the present invention is provided with a frequency dividing circuit on the side of the transmitting apparatus, which divides the frequency of the clock signal as an electric signal by two and gives the divided clock signal to the photoelectric conversion element. In the receiving device, a multiplication circuit for multiplying the clock signal converted into the electric signal by two is provided, and the transmitted signal converted into the electric signal is latched in synchronization with the doubled clock signal. Therefore, in the transmitter and the receiver, the frequency required for the photoelectric conversion element for the clock signal is half the frequency of the clock signal given as the electric signal, and is required for the conversion of the transmitted signal. Match the frequency. Therefore, even when the photoelectric conversion element for the clock signal and the photoelectric conversion element for the transmitted signal synchronized with the clock signal have the same configuration, the maximum transmission speed at which the photoelectric conversion element can operate is It is possible to set the transmission speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of an optical transmission device of the present invention.

FIG. 2 is a circuit diagram showing electrical connection of one embodiment of a frequency dividing circuit.

FIG. 3 is a timing chart showing timings of main signals according to an embodiment of the present invention.

FIG. 4 is a circuit diagram showing an electrical connection of a second embodiment of the multiplication circuit.

5 is a timing chart showing the relationship between the delay time of the multiplier circuit shown in FIG. 4 and the cycle of the clock signal.

FIG. 6 is a block diagram showing an electrical configuration of a conventional technique.

FIG. 7 is a timing chart showing timings of main signals in the conventional technique.

[Explanation of symbols]

 11 transmitter 12 frequency divider circuit 13 photoelectric conversion element 14 photoelectric conversion element 15 multiplication circuit 16 receiver 43 photoelectric conversion element 44 optical fiber cable 46 to 48 photoelectric conversion element 600 clock signal 601 to 608 data signal as transmitted signal 609 received Control signal as transmission signal 610 1/2 frequency-divided clock signal 730 Clock signal multiplied by 2

Claims (1)

[Claims] 1. A transmission device, in which a clock signal and a signal to be transmitted synchronized with this clock signal are guided as electric signals, and these two kinds of signals thus guided are converted into optical signals by using a photoelectric conversion element, and an optical device. A receiving device which converts an optical signal from the transmitting device guided through a fiber cable into an electric signal using a photoelectric conversion element and latches the converted transmitted signal in synchronization with the converted clock signal. In the optical transmission device, the transmitting device is provided with a frequency dividing circuit that divides the clock signal as an electric signal by two and gives the divided clock signal to the photoelectric conversion element. The device is provided with a multiplication circuit for multiplying a clock signal converted into an electric signal by 2. The receiving device is converted into an electric signal in synchronization with the doubled clock signal. The optical transmission apparatus characterized by latching the target transmission signal.