JPH04239233A - Optical receiving system - Google Patents

Abstract

PURPOSE:To provide the optical receiving system capable of using for general purpose in an optical communication system with different data transfer speeds. CONSTITUTION:A photo diode 1 is equipped with the sensitivity in a band capable of covering every transfer speed and an amplifier circuit 2 is equipped with a gain in the similar band. Further, as a low-pass filter 3, plural filters equipped with transmission characteristic in the band corresponding to respective transfer speeds are provided on a chip condenser, chip resistance, etc., and selected to be interposed between an amplifier circuit 2 and a comparator 4 according to the band corresponding to the transfer speed of the optical communication system using this filter. Thus, a band of the signal to be inputted to the comparator 4 is set so as to be matched to the transfer speed of the optical communication system to be applied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiving system used in an optical communication system.

0002

[Prior Art] An optical receiver used in optical communications includes a photodiode that photoelectrically converts a digital signal from an optical fiber, an amplifier circuit that amplifies this output (photoelectric conversion output), and this amplified output that is input. A comparator is used that outputs a standardized digital electrical signal. Incidentally, the optical signal inputted from the optical fiber to the photodiode includes so-called noise in addition to the original optical signal (digital optical signal), that is, transmission information in optical communication. Therefore, in order to remove this noise component, a photodiode that has sensitivity only in a band related to data transmission is used, and an amplifier circuit that has gain only in the band related to data transmission is used.

On the other hand, in order to remove the noise component and make it possible to receive only the signal component, it is possible to use a filter means such as a low-pass filter. Are known. It is thought that if such a filter is used, it will be possible to receive an optical signal in a desired band without particularly limiting the band of the photodiode or amplifier circuit.

0004

[Problems to be Solved by the Invention] However, according to the conventional technology, when manufacturing optical receivers used in optical communication systems with a wide variety of transmission speeds, it is necessary to individually select components and design circuits. No. In other words, if an optical receiver is designed with a photodiode and amplifier circuit that can only work in the band corresponding to a specific transmission speed, it cannot be used in optical communication systems with other transmission speeds and must be redesigned from scratch. Must be. Such inconveniences can be overcome by using filters as described above, but in conventional filters, the filters are built into the optical receiver, and photodiodes and amplifier circuits are also compatible with various transmission speeds. It's not designed to do that. For this reason, when the manufactured optical receiver is applied to the construction site of an optical communication system, there is a drawback that it cannot be used universally in systems with various transmission speeds.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical reception system that can be used for general purpose in optical communication systems with different data transmission speeds.

[0006]

[Means for Solving the Problems] The optical receiving system according to the present invention includes a photodetector that photoelectrically converts a digital optical signal, an amplifier circuit that amplifies the photoelectric conversion output, and a predetermined frequency component of the amplified output that is removed. Data transmission at a predetermined transmission rate is achieved by using an optical receiver having a filter means for outputting a digital signal and a comparator means for outputting a digital electrical signal that is a normalized output signal of the photodetector based on the output of the filter means. In the optical reception method of an optical communication system that performs As a means, a plurality of filters having pass characteristics in bands corresponding to each of a plurality of transmission speeds are prepared, and the filters are selected according to the band corresponding to the transmission speed used in the optical communication system, and the amplifier circuit and the comparator are connected to each other. It is characterized in that the band of the signal input to the comparator is set by interposing it between the means.

[0007]

[Operation] According to the present invention, the photodetector and the amplifier circuit are
It is applicable to a plurality of transmission speed bands in an optical communication system, and a plurality of filters that can be applied to each transmission speed are prepared as filter means. Therefore, by selectively applying filters depending on the transmission speed, the optical receiver can be adapted for use in optical communication systems with different bands. Furthermore, by configuring this filter with chip-shaped electronic components and preparing a substrate for each band that uses the chip-shaped electronic components to act as a filter, it is easy to apply it to optical communication systems with different transmission speeds. There is.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a circuit diagram showing the configuration of an optical receiver applied to the method of the embodiment. The optical receiver consists of a photodiode 1 which is a photodetector, an amplifier circuit 2 which amplifies this output, a low pass filter 3 which cuts high frequency components of the amplified output, and a comparator 4 which normalizes this output. be done. This optical receiver is used in a relay station or a receiving terminal of an optical communication system, and an optical signal transmitted through an optical fiber 5 is input to a photodiode 1. Here, this optical signal is attenuated due to transmission loss or contains noise, resulting in a degraded waveform as a digital signal. In the embodiment, this waveform is directly amplified by the amplifier circuit 2. The low-pass filter 3 is composed of a chip coil 3a with an inductance L and a chip capacitor 3b with a capacitance C, and therefore cuts high frequency components determined by the capacitance C and the inductance L. Therefore, high frequency noise components are removed and only the digital signal, which is a low frequency component, is input to the comparator 4. Therefore, the comparator 4 normalizes only the original signal and inputs it to the outside.

In such an optical communication system, in the present invention, the photodiode 1 and the amplifier circuit 2 are configured to be usable in bands corresponding to a plurality of transmission speeds, and the low-pass filter 3 is selected for each band. Configure as applicable. For example, when the data transmission speeds in three optical communication systems are S1, S2, and S3 (bps),
The corresponding frequency bands are F1, F2, F3 (H
z). At this time, the photodiode 1 and the amplifier circuit 2 are ones that can be applied to any of the frequencies F1 to F3 (wideband ones), and the low-pass filter 3 is a low-pass filter 31 consisting of a chip coil 3a1 and a chip capacitor 3b1. A low-pass filter 32 consisting of a chip coil 3a2 and a chip capacitor 3b2, and a low-pass filter 33 consisting of a chip coil 3a3 and a chip capacitor 3b3 are prepared. And inductance L1, L2, L3, capacitance C1, C2 respectively
, C3 are determined by low-pass filters 31 , 32 ,
33, frequencies F1, F2, F3,
are included, and their high frequency components are cut.

[0010] By doing so, the optical receiver of the embodiment can be universally applied to three optical communication systems. That is, in a system with a transmission speed S1, the chip coil 3a
1 and a low-pass filter 31 using a chip capacitor 3b1.
, S3 use optical receivers including low-pass filters 32, 33.

A partial change in the configuration of such an optical receiver is as follows:
For example, perform as shown in FIG. First, ceramic plate 31
is prepared, metalized here, and wiring 3 is applied. This is then used as a substrate for the low-pass filter 3, and connected as shown in FIG. 1 and incorporated into an optical receiver. Next, once the transmission speed of the applied optical communication system is determined, chip coils 3a1 to 3a3 and chip capacitors 3b1 to 3b3 corresponding to the transmission speed are mounted on the ceramic plate 31. Incidentally, such a band setting of the low-pass filter 3 may be performed before the optical receiver is shipped, or may be performed at the site immediately before it is actually applied to an optical communication system.

[0012] Filter characteristics setting for band setting may be performed for each filter as shown in FIG. As shown in the figure, there are three types of optical communication systems in which optical receivers are expected to be applied.
Ceramic plates 311 to 31 each have a low-pass filter 3 configured separately according to the transmission speeds S1 to S3.
Prepare 3. And this chip coil 3a1 ~
3a3 and chip capacitors 3b1 to 3b3 are connected to each other by metallized wirings 321 to 323, respectively. By selecting ceramic plates 311 to 313 and mounting them on an optical receiver, versatility is achieved. enhance

The above embodiment will be explained in more detail as follows. That is, the data transmission speed in the first optical communication system is 220 Mbps, and the data transmission speed in the second optical communication system is 220 Mbps.
The data transmission speed in the optical communication system is 125M
bps, the corresponding frequency band is empirically about 150 MHz for the first optical communication system and about 90 MHz for the second optical communication system. Therefore,
The photodiode 1 and amplifier circuit 2 of the optical receiver are designed to have sensitivity and gain in a band of 220 MHz or less to cover these, and the low-pass filter 3 of the optical receiver used in the first optical communication system is , inductance L=220nH, capacitance C=2p
The low-pass filter 3 of the optical receiver used in the second optical communication system is composed of chip-shaped electronic components having an inductance L of 390 nH and a capacitance C of 2 pF. As a result, noise components exceeding 150 MHz are cut in the first optical communication system, and noise components exceeding 90 MHz are cut in the second optical communication system.

In the above embodiment, a low-pass filter is used to cut only high-frequency components whose frequencies exceed the transmission band, but in order to simultaneously cut low-frequency components below the transmission band, a so-called band-pass filter is used. may also be used.

[0015]

[Effects of the Invention] As explained above in detail, the present invention provides
The photodetector and the amplifier circuit are applicable to a plurality of transmission speed bands, and the filter means is provided with a plurality of filters applicable to each transmission speed. Therefore, by selectively applying filters, the optical receiver can be adapted for use in each band. Furthermore, by constructing this filter with chip-shaped electronic components and preparing a substrate for each band that uses the chip-shaped electronic components to function as a filter, application to systems with different transmission speeds is facilitated. Therefore, it is possible to realize an optical reception method that can be used universally in optical communication systems with different data transmission speeds.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating main parts of the embodiment.

FIG. 3 is a diagram illustrating main parts of the embodiment.

[Explanation of symbols]

1...Photodiode 2...Amplification circuit 3...Low pass filter 4...Comparator 5...Optical fiber

Claims (3)

[Claims] 1. A photodetector that photoelectrically converts a digital optical signal, an amplifier circuit that amplifies the photoelectric conversion output, and a filter that removes a predetermined frequency component of the amplified output.
By using an optical receiver having a comparator means for outputting a digital electrical signal that normalizes the output signal of the photodetector based on the output of the filter means,
In an optical reception system for an optical communication system that transmits data at a predetermined transmission rate, the photodetector is made sensitive in a band that can cover all of a plurality of transmission rates, and the amplifier circuit is made to have sensitivity in a band that can cover all of the plurality of transmission rates. A plurality of filters having a gain in a band and a pass characteristic in a band corresponding to each of the plurality of transmission speeds are prepared as the filter means, and these filters are used in an optical communication system in which the optical receiver is used. An optical receiving system characterized in that a band of a signal input to the comparator means is set by selecting a band corresponding to a data transmission speed and inserting the selected signal between the amplifier circuit and the comparator means. 2. Setting the band by inserting the filter between the amplification circuit and the comparator means is achieved by inserting a chip-shaped electronic device into a substrate prepared in advance in the optical receiver to configure the filter. 2. The optical receiving system according to claim 1, wherein the optical receiving system is implemented by mounting components. 3. Setting the band by inserting the filter between the amplifier circuit and the comparator means, a substrate prepared in advance by mounting a chip-shaped electronic component as the filter is used as the optical receiver. Claim 1, characterized in that the method is carried out by being mounted in a container.
Optical reception method described.