JP2001036142A - Light source for optical communication system and optical communication system - Google Patents

Abstract

(57) [Problem] To suppress the influence of the transmission loss characteristic of an optical signal in an optical transmission line even in a use environment where the temperature changes arbitrarily within a predetermined range, such as a vehicle, to achieve a large capacity and high density. An optical communication system capable of realizing information transmission with high accuracy, and a light source suitable for such an optical communication system. SOLUTION: In consideration of the transmission loss characteristic of an optical fiber 7 used for transmitting an optical signal from an optical transmission module 3 to an optical reception module 5, the temperature environment of the vehicle in which the optical communication system 1 is mounted is -40. In the range of ゜ C to + 85 ° C, the fluctuation range of the transmission loss of the optical fiber 7 is 12d at the maximum.
B / km (± 6 dB / km)
The blue LED 35 whose center emission wavelength fluctuates only within the range of 634.4 nm to 654.1 nm is used as the emission light source of the light transmission module 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system for outputting an optical signal modulated according to transmission information from a light source toward an optical transmission line, and a light source suitable for use in the optical communication system. The present invention relates to an optical communication system and a light source for an optical communication system which are suitable for use in an environment where the temperature changes arbitrarily within a predetermined range.

[0002]

2. Description of the Related Art In recent years, in the field of information transmission, an optical communication system using an optical signal instead of a conventional electric signal has begun to be widely used in response to an increase in the capacity and density of the transmitted information. Regarding an in-vehicle LAN that transmits switch information and the like for driving a load, introduction of an optical communication system has been studied and partially implemented.

In the case where the space for laying the optical transmission line is limited as in a vehicle, a plastic optical fiber which is flexible and has a high degree of freedom in laying is likely to be used. Red LED commonly used as a light source for optical signals in plastic optical fibers
In the light emission wavelength region, there is a characteristic that the amount of transmission loss greatly changes due to a change in wavelength.

[0004]

Therefore, in an environment where the temperature changes due to the outside temperature or the radiant heat of a vehicle-mounted object such as a vehicle, the above-described red LED is used unless a temperature compensation circuit or the like is provided. An optical communication system using a plastic optical fiber as a light source as an optical signal light source cannot be operated.

[0005] In other words, when constructing an optical communication system, if the specifications of the light source of the optical signal are not set in consideration of the use environment and the compatibility with the optical transmission line, a large-capacity, high-density optical system is required. Information transmission cannot be realized with stable accuracy.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a large-capacity, high-density information transmission by suppressing the influence of the transmission loss characteristic of an optical signal in an optical transmission line even in a usage environment in which the temperature changes arbitrarily within a predetermined range such as a vehicle. An object of the present invention is to provide an optical communication system that can be realized with high accuracy and a light source suitable for such an optical communication system.

[0007]

The present invention described in each of claims 1 and 2 for achieving the above-mentioned object relates to a light source for an optical communication system, and the present invention described in claim 3 relates to an optical communication system. It is about.

The light source for an optical communication system according to the first aspect of the present invention is modulated in accordance with transmission information in an optical communication system used in a usage environment in which the temperature changes arbitrarily within a predetermined range. A light source used to output an optical signal toward an optical transmission line, the light source being configured by a light emitting element that changes a wavelength of the optical signal within a predetermined wavelength range according to a temperature change within the predetermined range. Wherein the predetermined wavelength range is set to a range in which the fluctuation range of the transmission loss of the optical signal in the optical transmission line according to the fluctuation of the wavelength of the optical signal is equal to or less than a predetermined allowable value. And

According to a second aspect of the present invention, there is provided the light source for an optical communication system according to the first aspect of the present invention, wherein the optical transmission line is required to be at a temperature within the predetermined range. It is constituted by a plastic optical fiber having heat resistance of the predetermined wavelength range,
It is determined according to the transmission loss characteristic of the optical signal in the plastic optical fiber.

Further, according to a third aspect of the present invention, an optical communication system according to the present invention transmits a light source used to output an optical signal modulated according to transmission information, and transmits the optical signal output from the light source. In an optical communication system having an optical transmission path and used in a usage environment in which the temperature is arbitrarily changed within a predetermined range, the light source has a wavelength of the optical signal corresponding to a temperature change within the predetermined range. The light-emitting element has a variation within a predetermined wavelength range, and the predetermined wavelength range is such that a variation width of the transmission loss of the optical signal in the optical transmission line according to the variation of the wavelength of the optical signal has a predetermined tolerance. It is characterized in that it is set in a range below the value.

According to the light source for an optical communication system of the present invention described in claim 1, according to a temperature change within a predetermined range,
When the wavelength of the optical signal output from the light emitting element constituting the light source fluctuates within a predetermined wavelength range, the fluctuation width makes the transmission loss fluctuation width of the optical signal in the optical transmission line of the optical communication system equal to or less than a predetermined allowable value. It will fall within the range.

Further, according to the light source for an optical communication system of the present invention described in claim 2, in the light source for an optical communication system of the present invention described in claim 1, the light is transmitted through a plastic optical fiber having a required heat resistance. When configuring a transmission line, if the range in which the wavelength of the optical signal output from the light emitting element fluctuates with a temperature change within a predetermined range is determined according to the transmission loss characteristic of the optical signal in the plastic optical fiber, the plastic optical fiber The transmission loss fluctuation range of the optical signal actually occurring in the fiber falls below a predetermined allowable value.

Further, according to the optical communication system of the present invention, the wavelength of the optical signal output from the light emitting element constituting the light source falls within the predetermined wavelength range according to the temperature change within the predetermined range. , The fluctuation range of the transmission loss of the optical signal in the optical transmission line falls below a predetermined allowable value.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical communication system according to the present invention, together with a light source for an optical communication system, will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical communication system according to an embodiment of the present invention. The optical communication system of this embodiment, which is denoted by reference numeral 1 in FIG. Used for information transmission, multiple nodes 1
a, 1b, 1c, 1d. The optical transmission module 3 of each node 1a, 1b, 1c, 1d and the optical reception module 5 of each of the other nodes 1a, 1b, 1c, 1d are An optical network is formed by connecting optical fibers 7 for transmitting optical signals.

FIG. 2 shows a certain node 1a, 1b, 1 in FIG.
c, 1d optical transmission module 3 and some other node 1
FIG. 3 is an explanatory diagram showing, in partial blocks, a connection relationship between a, 1b, 1c, and 1d with the optical receiving module 5, and as shown in FIG. 2, each optical fiber 7 is optically coupled to the optical transmitting module 3. An optical connector 71 and an optical connector 73 optically coupled to the optical receiving module 5 are provided at both ends.

The optical transmission module 3 includes nodes 1a,
A signal input terminal 31 to which a transmission signal generated by a controller (not shown) of 1b, 1c, 1d is digitally input, a drive circuit 33 for modulating a drive signal by the digital transmission signal input to the signal input terminal 31, A blue LED 35 that is driven to emit light by a modulated drive signal from the drive circuit 33 and outputs an optical signal.

The optical receiving module 5 includes a pin photodiode 51 for receiving an optical signal from the optical transmitting module 3 input through the optical connector 73 of the optical fiber 7, and the pin photodiode 51 performs photoelectric conversion. Amplifying circuit 53 for amplifying the amplified reception signal, and an A / D for digitally converting the reception signal amplified by the amplification circuit 53
A conversion circuit 55 and a reception signal digitally converted by the A / D conversion circuit 55 are used as a digital reception signal at the node 1.
a, 1b, 1c, and 1d, and a signal output terminal 57 that is output to a controller (not shown).

In the present embodiment, the optical fiber 7 is formed of P
The optical fiber 7 is a plastic optical fiber made of MMA (polymethyl methacrylate). The optical fiber 7 is shown in the graph of FIG. 3 in which the vertical axis indicates the transmission loss (dB / km) and the horizontal axis indicates the wavelength (nm). It has such transmission loss characteristics.

In the optical communication system 1 of the present embodiment, the temperature of the vehicle on which the optical communication system 1 is mounted is −40 as the blue LED 35 of the optical transmission module 3.
Between ゜ C and +85 ゜ C, the fluctuation range of the transmission loss in the graph of FIG. 3 is 12 dB / km (± 6 dB /
km) (equivalent to a range of not more than a predetermined allowable value in the claims), the center emission wavelength at a standard temperature of 25 ° C. is 470 nm ± 5 nm, and -4 nm.
The emission wavelength fluctuation range between 0 ° C and + 85 ° C is ±
1.3 nm one is used.

In other words, the center emission wavelength of the blue LED 35 between -40 ° C. and + 85 ° C. is 470 nm.
± 6.3 nm = 463.7 nm to 476.3 nm, and as can be seen from the graph of FIG. 3, the fluctuation range of the transmission loss in the central emission wavelength range is 12 at maximum.
117 within the range of dB / km (± 6 dB / km)
dB / km to 129 dB / km.

In the evaluation of the transmission loss characteristics of the optical fiber 7 for obtaining the graph of FIG. 3, the excitation N having a relatively high directivity is used as a light source for outputting light having a wavelength within the evaluation range.
Since the LED of A = 0.1 is used, the transmission loss value generally shows a good value for each wavelength.

Therefore, when the transmission loss characteristic of the optical fiber 7 is evaluated using an LED having lower directivity than the LED used to obtain the graph of FIG. 3, the volume of the transmission loss naturally increases. Although it should be relatively higher than the value shown in the graph of FIG. 3, even in this case, the relationship between the transmission loss values between the respective wavelengths is higher than that shown in FIG. It will not change.

Next, the operation (operation) of the optical communication system 1 according to the present embodiment having the above configuration will be described.

In the optical communication system 1 of the present embodiment, when the operating temperature environment of the optical communication system 1 varies between -40 ° C. and + 85 ° C. depending on the condition of the vehicle, the blue LED 35 of the optical transmission module 3 is turned on. The center emission wavelength of the optical signal that is driven to emit light by the drive signal from the drive circuit 33 modulated by the digital transmission signal and is output is:
463.7 nm to 476.3 nm, so that the transmission loss in the optical fiber 7 is 117 dB.
/ Km to 129 dB / km.

Therefore, the reception signal received by the pin photodiode 51 of the optical receiving module 5 is -40.degree.
117 dB at any temperature between ~ + 85 ° C
/ Km to 129 dB / km.

Therefore, after being amplified by the amplification circuit 53, A
The level of the digital reception signal converted by the / D conversion circuit 55 and output from the signal output terminal 57 is also in a range corresponding to a maximum transmission loss variation range of 12 dB / km of the optical signal from the blue LED 35 in the optical fiber 7. It only fluctuates.

For reference, assuming that a general red LED is used for the light transmitting module 3 instead of the blue LED 35, the temperature dependence of the emission wavelength of the red LED is generally 0.2 nm / ° C. According to this, the center emission wavelength at a standard temperature of 25 ° C. is 650.
nm, the center emission wavelength of the red LED between −40 ° C. and + 85 ° C. is 650 nm + 4.1 n
m, 650 nm-15.6 nm = 634.4 nm-65
It is in the range of 4.1 nm.

Then, as is apparent from the graph of FIG. 3, the fluctuation range of the transmission loss in the central emission wavelength region of 634.4 nm to 654.1 nm is 12 dB / max at the maximum.
km (± 6 dB / km),
133 dB / km to 340 dB / km.

As described above, the optical communication system 1 of the present embodiment
According to the above, from the optical transmitting module 3 to the optical receiving module 5
In consideration of the transmission loss characteristics of the optical fiber 7 used for transmitting the optical signal to the optical fiber 7, the optical fiber 7 is used in a temperature range of −40 ° C. to + 85 ° C., which is the temperature environment of the vehicle on which the optical communication system 1 is mounted. 12dB maximum variation in transmission loss
/ Km (± 6 dB / km).
The blue LED 35 whose center emission wavelength fluctuates only within the range of 34.4 nm to 654.1 nm is used as a light source of the light transmission module 3.

Therefore, even if the operating temperature environment of the optical communication system 1 fluctuates between −40 ° C. and + 85 ° C. depending on the condition of the vehicle, the transmission loss in the optical fiber 7 is reduced by 1 at the maximum.
117 dB / k which becomes 2 dB / km (± 6 dB / km)
m to 129 dB / km, large-capacity, high-density information transmission can be realized with high accuracy.

In the present embodiment, the allowable variation range of the transmission loss of the optical fiber 7 is 12 dB / km (± 6 dB) at the maximum.
B / km), and the allowable fluctuation range of the center emission wavelength of the blue LED 35 under the temperature environment of −40 ° C. to + 85 ° C. is set to 47 at the standard temperature of 25 ° C.
The maximum value is ± 1.3 nm assuming that it is 0 nm ± 5 nm, but these values are appropriately changed according to the transmission loss characteristics of the optical transmission line to be used and the assumed operating temperature environment of the optical communication system.

In this embodiment, a plastic optical fiber made of PMMA is used as the optical fiber 7, and the blue LED 35 is used as the light source of the light transmitting module 3 according to this. As the light transmission path, a plastic optical fiber made of a material other than PMMA is used, and accordingly, a light emitting element such as an LED that emits light other than blue light, such as green light or red light, may be used as the light emitting light source of the light transmitting module 3. Good.

In this case, it is important that the transmission loss in the optical transmission line can be suppressed within a certain range even if the operating temperature environment of the optical communication system fluctuates within a predetermined range depending on the condition of the vehicle. It is to select a light emitting element whose emission center wavelength fluctuates within an appropriate range according to the transmission loss characteristics with respect to the wavelength of the optical transmission line. Examining whether to use it has no meaning at all.

Further, in the present embodiment, the optical communication system 1 mounted on a vehicle has been described as an example.
It goes without saying that the present invention is widely applicable not only to vehicles but also to optical communication systems used under usage environments where the temperature arbitrarily changes within a predetermined range.

[0036]

As described above, according to the light source for an optical communication system according to the first aspect of the present invention, the light transmission in an optical communication system used in an operating environment where the temperature arbitrarily changes within a predetermined range. A light source used to output an optical signal modulated in accordance with information toward an optical transmission line, wherein a change in the wavelength of the optical signal according to a temperature change in the predetermined range is within a predetermined wavelength range. Wherein the predetermined wavelength range is within a range in which the fluctuation range of the transmission loss of the optical signal in the optical transmission line according to the fluctuation of the wavelength of the optical signal is equal to or less than a predetermined allowable value. The configuration has been set.

For this reason, the fluctuation width of the output signal wavelength by the light emitting element according to the temperature change within the predetermined range is set so that the transmission loss fluctuation width of the optical signal in the optical transmission line of the optical communication system is equal to or less than a predetermined allowable value. Within this range, large-capacity, high-density information transmission can be realized in the optical communication system with high accuracy.

According to the light source for an optical communication system of the present invention described in claim 2, in the light source for an optical communication system of the present invention described in claim 1, the optical transmission line has a temperature within the predetermined range. , And the predetermined wavelength range is determined according to the transmission loss characteristic of the optical signal in the plastic optical fiber.

For this reason, the variation range of the output signal wavelength by the light emitting element according to the transmission loss characteristics of the plastic optical fiber used as the optical transmission line is set so that the variation range of the transmission loss of the plastic optical fiber is not more than a predetermined allowable value. Can be suppressed within.

Further, according to the optical communication system of the present invention, a light source used to output an optical signal modulated according to transmission information, and an optical signal output from the light source An optical communication system having an optical transmission path for transmission and used in an operating environment in which the temperature is arbitrarily changed within a predetermined range, wherein the light source is configured to transmit the optical signal according to a temperature change within the predetermined range. The light-emitting element has a wavelength variation within a predetermined wavelength range, and the predetermined wavelength range is such that a variation width of the transmission loss of the optical signal in the optical transmission line according to the wavelength variation of the optical signal is a predetermined value. Is set to be within the range of the allowable value or less.

For this reason, the fluctuation width of the output signal wavelength by the light emitting element according to the temperature change within the predetermined range is suppressed within a range where the fluctuation width of the transmission loss of the optical signal in the optical transmission line is equal to or less than a predetermined allowable value. Thus, large-capacity, high-density information transmission can be realized with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical communication system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing, in partial blocks, a connection relationship between a certain node in FIG. 1 and an optical receiving module of another certain node.

FIG. 3 is a graph showing transmission loss characteristics of the optical fiber of FIG. 1 with transmission loss on the vertical axis and wavelength on the horizontal axis.

[Explanation of symbols]

 Reference Signs List 1 optical communication system 35 blue LED (light source, light emitting element) 7 optical fiber (optical transmission line, plastic optical fiber)

Claims (3)

[Claims] 1. A light source used for outputting an optical signal modulated according to transmission information to an optical transmission line in an optical communication system used in a usage environment in which the temperature changes arbitrarily within a predetermined range. And a light-emitting element configured to change the wavelength of the optical signal according to a temperature change within the predetermined range within a predetermined wavelength range, wherein the predetermined wavelength range is the fluctuation of the wavelength of the optical signal. Wherein the variation range of the transmission loss of the optical signal in the optical transmission line according to the above is set within a range of not more than a predetermined allowable value. 2. The optical transmission line is formed of a plastic optical fiber having a required heat resistance at a temperature within the predetermined range, and the predetermined wavelength range is determined by a transmission loss characteristic of the optical signal in the plastic optical fiber. The light source for an optical communication system according to claim 1, wherein the light source is determined according to: 3. A light source used for outputting an optical signal modulated in accordance with transmission information, and an optical transmission line for transmitting an optical signal output from the light source, wherein the temperature is within a predetermined range. In an optical communication system used under an arbitrarily changing use environment, the light source is configured by a light-emitting element that causes a wavelength change of the optical signal according to a temperature change within the predetermined range to be within a predetermined wavelength range. Wherein the predetermined wavelength range is set to a range in which the fluctuation range of the transmission loss of the optical signal in the optical transmission line according to the fluctuation of the wavelength of the optical signal is equal to or less than a predetermined allowable value. Optical communication system.