JP2001027745A - Light transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reduction in size and weight of a light transmitter used for a high-speed light transmission system. SOLUTION: This light transmitter comprises a code converter 7 for code- converting a binary data signal S1 into a ternary data signal S2, a code converter 8 for converting an inverted binary data signal S1' into an inverted ternary data signal S2', an electro-optical converter 1 for converting an electric signal into an optical signal and outputting it, an optical de-multiplexer 2 for de-multiplexing the optical signal from the electro-optical converter 1, an EA (electro-absorption type) optical modulator 3 for modulating one de-multiplexed optical signal by the ternary data signal S2, a phase shifter 11 for inverting the phase of the other de-multiplexed optical signal, an EA modulator 4 for modulating the phase-inverted optical signal by the inverted ternary data signal S2', and an optical multiplexer 5 for outputting an optical duo-binary signal S3 multiplexing the optical signals from the EA converters 3, 4 to an optical fiber 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device for converting an electric signal, which is a data input signal, into an optical signal and outputting the same, and more particularly, to an optical transmission system used in an optical transmission system having a transmission speed of 2.5 GHz or more. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, in an optical transmission system for high-speed transmission, a data input signal that is a binary data signal is converted into a ternary duobinary signal, and the converted duobinary signal is subjected to phase modulation. 2. Description of the Related Art An optical transmitter that outputs a duobinary signal is known. Such an optical transmission device is disclosed in, for example, a document “Characteristics of a terabit optical duobinary signal in a high-efficiency WDM system”.
(Ono et al., IEEE JOUNAL OFLIGHTWAVE TECHNOLOGY, VOL.1
6, NO. 5, pp. 788-797 MAY 1998).

A duobinary code is a kind of band compression code, and its occupied band is compressed to about half of a normal binary data signal. Therefore, the optical duobinary signal has higher resistance to the chromatic dispersion of the optical fiber than the binary intensity modulated signal, and can overcome the limit of the transmission distance due to the chromatic dispersion of the optical fiber.

FIG. 13 is a block diagram showing an example of the configuration of a conventional optical transmission device, and FIG. 14 is a diagram showing signal waveforms generated at various parts in FIG. 13 and 14
, The binary data signal S from the data input terminal 109
The binary data signal S101 is input to the code converter 1 constituted by a low-pass filter LPF.
07 is converted into a ternary data signal S102. On the other hand, the inverted data input terminal 110 is connected to the data input terminal 1
An inverted binary data signal S101 ′ obtained by inverting the binary data signal S101 input from S09 is input, and is converted into a ternary data signal S102 ′ by a code converter 108 including a low-pass filter LPF. The low-pass filter LPF has, for example, a band of about ４ of the transmission rate, and converts the binary data signal S101 shown in FIG. 14 into a ternary data signal (duobinary signal) shown in FIG.
Convert to S102.

[0005] The electrical / optical converter 101 converts the electrical signal into an optical signal in accordance with the input electrical signal, and inputs the optical signal to the LN converter 115. The LN converter 115 is composed of LiNb
Using an O ₃ ferroelectric crystal, modulation is performed according to the electro-optical conversion characteristics due to the electro-optical effect. That is, the LN converter 115 is input from the electrical / optical converter 101 by the ternary data signal S102 input from the code converter 107 and the inverted ternary data signal S102 ′ input from the code converter 108. The optical signal is modulated, and the modulated optical duobinary signal S103 is
Is guided.

Further, referring to FIG. 15, LN modulator 11
Operation 5 will be described. In FIG. 15, since the ternary data signal S102 and the inverted ternary data signal S102 'are input to the LN modulator 115, each signal S10
2, S102 ′ is a bias characteristic of the LN modulator 115,
That is, it is driven in a push-pull manner by the electrical / optical conversion input / output characteristics. As a result, the codes corresponding to the codes “1”, “0”, and “−1” of the ternary data signal S102 are converted into light signals having light intensities of “1”, “0”, and “1”. , Ternary data signal S10 by push-pull drive
The signs “1” and “−1” of 2 are “0” and “π”, respectively.
Is converted into an optical signal having the phase of That is, the ternary “1”, “0”, and “−1” of the ternary data signal S102 are L
By the N modulator 115, three values “1-0”,
It is converted into “0” and “1-π” and output as an optical duobinary signal S103. Note that “1-0” indicates a value where the light intensity (amplitude) is “1” and the phase is “0”,
“1-π” indicates a value whose amplitude is “1” and whose phase is “π”.

[0007]

However, in the above-mentioned conventional optical transmitter, since an LN modulator is used as an optical modulator, an amplifier and a bias circuit (not shown) for generating a large driving voltage are required. However, there has been a problem that the circuit scale of the entire optical transmission device becomes large and power consumption is large.

[0008] The present invention has been made in view of the above,
An optical transmission device used for a high-speed optical transmission system,
It is an object of the present invention to obtain an optical transmitter capable of realizing a reduction in size and weight.

[0009]

To achieve the above object, an optical transmitting apparatus according to the present invention comprises: a first code converter for performing code conversion of a data input signal; and a code converter for inverting the data input signal. A second code converter for performing conversion, an electric / optical converter for converting an electric signal into an optical signal and outputting the same, and a first optical coupler for splitting the optical signal output from the electric / optical converter A first electro-absorption optical modulator that modulates one optical signal split by the first optical coupler with a code conversion signal output from the first code converter; and A phase shifter for inverting the phase of the other optical signal split by the optical coupler, and modulating the optical signal, the phase of which has been inverted by the phase shifter, with a code conversion signal output from the second code converter. The second electroabsorption optical modulator and the front A second optical coupler and outputting the multiplexed modulated light signal by the first electroabsorption optical modulator and said second electroabsorption optical modulator, and further comprising a.

According to the present invention, the data input signal is code-converted by the first code converter, and this code converted signal is input to the first electro-absorption optical modulator and the second code converter. Code conversion of the inverted signal of the data input signal, and this code conversion signal is input to the second electro-absorption optical modulator. On the other hand, the optical signal output from the electric / optical converter is split into two optical signals by the first optical coupler, and one optical signal is input to the first electro-absorption optical modulator, and the other is input. After the optical signal is inverted in phase by the phase shifter, it is input to the second electro-absorption optical modulator. The first electro-absorption optical modulator modulates the optical signal with the code conversion signal output from the first code converter, and the second electro-absorption optical modulator outputs the signal from the second code converter. The second optical coupler modulates the optical signal whose phase is inverted by the code conversion signal, and outputs the optical signal output from the first electro-absorption optical modulator and the optical signal output from the second electro-absorption optical modulator. Multiplexed optical signals and output them.Using an electro-absorption optical modulator that does not require a large driving voltage as the optical modulator, an amplifier or bias voltage circuit for generating a large driving voltage is used. Not required.

[0011] In the optical transmitter according to the next invention, in the above invention, the phase shifter is connected between the second electro-absorption optical modulator and the second optical coupler. The optical signal modulated by the second electro-absorption type optical modulator is inverted in phase and output to the second optical coupler.

According to the present invention, the first electro-absorption optical modulator modulates one of the optical signals output from the first optical coupler by the code conversion signal output from the first code converter, A second electro-absorption optical modulator modulates the other optical signal output from the first optical coupler by a code conversion signal output from the second code converter, and a phase shifter controls the second electric field. Performs phase inversion of the optical signal modulated by the absorption type optical modulator, and the second optical coupler combines the optical signal output from the first electroabsorption type optical modulator with the optical signal output from the phase shifter. Are combined and output. An electro-absorption optical modulator that does not require a large driving voltage is used as the optical modulator, and an amplifier and a bias voltage circuit for generating a large driving voltage are not required.

[0013] An optical transmitter according to the next invention comprises a code converter for performing code conversion of a data input signal, a squarer for calculating and outputting a square value of a code conversion signal output from the code converter, and A code detector for detecting a code of a code conversion signal output from the converter, an electric / optical converter for converting an electric signal into an optical signal and outputting the same, and an optical signal output from the electric / optical converter. An electro-absorption optical modulator that modulates with a signal output from the squarer, and inverts the phase of an optical signal output from the electro-absorption optical modulator according to a code detected by the code detector. And an output phase shifter.

According to the present invention, the code converter performs code conversion of the data input signal, the squarer calculates and outputs the square value of the code converted signal, and the code detector performs the code conversion. The code of the code conversion signal is detected, and the electro-absorption optical modulator outputs an optical signal obtained by modulating the optical signal output from the electric / optical converter by the signal output from the squarer to the phase shifter, The phase shifter performs the phase inversion of the input optical signal according to the code detected by the code detection signal and outputs the inverted signal, and as an optical modulator, an electroabsorption modulator that does not require a large driving voltage. To eliminate the need for an amplifier or bias voltage circuit for generating a large driving voltage, and to use only one electro-absorption type optical modulator.

An optical transmitter according to the next invention comprises: a first code converter for performing code conversion on a data input signal; a second code converter for performing code conversion on an inverted signal of the data input signal; An exclusive OR circuit for calculating and outputting an exclusive OR of a code conversion signal output from a first code converter and a code conversion signal output from the second code converter; and the first code A code detector for detecting a code of a code conversion signal output from the converter or the second code converter, an electric / optical converter for converting an electric signal into an optical signal and outputting the same, and the electric / optical conversion An electro-absorption optical modulator that modulates an optical signal output from the detector by a signal output from the exclusive-OR circuit, and from the electro-absorption optical modulator according to a code detected by the code detector. Output optical signal A phase shifter which inverts the phase,
It is characterized by having.

According to the present invention, the first code converter performs code conversion of the data input signal, inputs the code-converted signal to one end of the exclusive OR circuit, and performs the second code conversion. Performs a code conversion on the inverted signal of the data input signal, inputs the code converted signal to the other end of the exclusive OR circuit, and the exclusive OR circuit outputs the signal from the first code converter. The exclusive-OR of the code conversion signal to be output and the code conversion signal output from the second code converter is output and input to the electro-absorption optical modulator. The optical signal output from the optical converter is modulated by the signal output from the exclusive OR circuit and output to the phase shifter, and the code detector is provided with a first code converter or a second code converter. Detects the sign of the sign conversion signal output from Is to invert the phase of the optical signal output from the electro-absorption optical modulator in accordance with the code detected by the code detector and output the signal, so that the optical modulator does not require a large driving voltage. A type optical modulator is used, an amplifier and a bias voltage circuit for generating a large driving voltage are not required, and only one electroabsorption type optical modulator is used.

In the optical transmitter according to the next invention, in the above invention, the phase shifter is connected between the electric / optical converter and the electro-absorption type optical modulator, and is operated by the code detector. The phase of an optical signal output from the electrical / optical converter is inverted according to the detected code, and the inverted signal is output to the electro-absorption optical modulator.

According to the present invention, the first code converter performs code conversion of the data input signal, and inputs the code-converted signal to one end of the exclusive OR circuit. Performs a code conversion on the inverted signal of the data input signal, inputs the code converted signal to the other end of the exclusive OR circuit, and the exclusive OR circuit outputs the signal from the first code converter. An exclusive OR of the code conversion signal to be output and the code conversion signal output from the second code converter is output and input to the electro-absorption optical modulator, and the code detector outputs the first code. The code of the code conversion signal output from the converter or the second code converter is detected, and the phase shifter detects the code of the optical signal output from the electrical / optical converter according to the code detected by the code detector. Perform phase inversion and output to electroabsorption optical modulator An electro-absorption optical modulator modulates an optical signal output from a phase shifter with a signal output from an exclusive OR circuit and outputs the modulated signal. As an optical modulator, an electric field that does not require a large driving voltage is used. The use of an absorption type optical modulator eliminates the need for an amplifier and a bias voltage circuit for generating a large drive voltage, and uses only one electroabsorption type optical modulator.

An optical transmitter according to the next invention is the above-mentioned invention, wherein the electro-optical converter, the first electro-absorption optical modulator, the second electro-absorption optical modulator, the electro-absorption Any one or more of the optical modulator and the phase shifter are configured on the same optical integrated circuit substrate.

According to the present invention, two or more of an electric / optical converter, a first electroabsorption optical modulator, a second electroabsorption optical modulator, an electroabsorption optical modulator, and a phase shifter are provided. Are configured on the same optical integrated circuit board, and components for handling light are integrated on the same optical integrated circuit.

In the optical transmitter according to the next invention, in the above invention, the data input signal is a binary data signal, and the code conversion signal is a ternary duobinary signal.

According to the invention, the data input signal is a binary data signal, and the code conversion signal is a ternary duobinary signal obtained by code conversion of the binary data signal. Is output as an optical duobinary signal including optical phase modulation.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Embodiment 1 First, a first embodiment of the present invention will be described. In the first embodiment, an electroabsorption optical modulator (hereinafter, referred to as an “EA modulator”) is used instead of the LN modulator used in the conventional optical transmission device.
The EA modulator is an optical modulator using a Stark effect or the like in which a light absorption coefficient changes according to an electric field applied to a substance, and has a lower driving voltage and a wider modulation band than an LN modulator. The EA modulator is realized by an InGaAlAs / InAlAs multiple quantum well device or the like.

FIG. 1 is a block diagram showing a configuration of an optical transmission apparatus according to Embodiment 1 of the present invention, and FIG.
FIG. 3 is a diagram showing signal waveforms generated by the respective units shown in FIG. In FIG. 1, a binary data signal S1 shown in FIG. 2 is input to a data input terminal 9, and the binary data signal S1 is input to a code converter 7 constituted by a low-pass filter LPF. On the other hand, an inverted binary data signal S1 'obtained by inverting the binary data signal S1 is input to the inverted data input terminal 10, and the inverted binary data signal S1' is sent to the code converter 8 constituted by a low-pass filter LPF. Is entered.

The code converter 7 converts the binary data signal S1 into a ternary data signal (duobinary signal) S2 shown in FIG.
And output. This ternary data signal S2 is
This is a ternary data signal having light intensity (amplitude) of “1”, “0”, and “−1”. On the other hand, the code converter 8 converts the inverted binary data signal S1 'into a ternary data signal S2' and outputs the converted signal.

The electric / optical converter 1 generates an optical signal corresponding to the input electric signal, and inputs the generated optical signal to a duplexer 2 realized by an optical coupler. Duplexer 2
Splits the input optical signal into two. One of the two split optical signals is input to the EA modulator 3. EA modulator 3
Modulates the optical signal input from the demultiplexer 2 with the ternary data signal S2 input from the code converter 7, and outputs the modulated signal to the multiplexer 5. The other optical signal that has been split into two is input to the phase shifter 11, which outputs an inverted optical signal obtained by inverting the phase of the optical signal input from the splitter 2 to the EA modulator 4. I do. The EA modulator 4 modulates the inverted optical signal with the inverted ternary data signal S 2 ′ input from the code converter 8 and outputs the modulated signal to the multiplexer 5. The multiplexer 5 includes the EA modulator 3
And the inverted optical signal output from the EA modulator 4 is multiplexed, and the multiplexed optical signal is guided to the optical fiber 6 as an optical duobinary signal S3 shown in FIG. The electrical signal of the binary data signal S1 is converted into an optical signal of the optical duobinary signal S3 and transmitted.

Further, referring to FIG. 3, EA modulators 3, 4
The operation of will be described. In FIG. 3, the EA modulator 3
Receives a ternary data signal S2, and applies a bias voltage to the ternary data signal S2 in accordance with the electro-optical conversion input / output characteristics of the EA modulator 3 so that " The value corresponding to -1 "is turned off,
The optical signal input from the duplexer 2 is output only when the ternary data signal S2 corresponds to “1”. That is, 3
Only when the value data signal S2 corresponds to "1", the bit "1-0" having the amplitude "1" and the phase "0" is output to the multiplexer 5 as an optical signal.

On the other hand, the inverted ternary data signal S2 'is input to the EA modulator 4, and a bias voltage is applied to the inverted ternary data signal S2' in accordance with the electrical-optical conversion input / output characteristics of the EA modulator 4. Is applied, the value corresponding to "1" of the inverted ternary data signal S2 'is turned off, and only when the inverted ternary data signal S2' corresponds to "-1",
An inverted optical signal whose phase has been inverted by the phase shifter 11 is output. That is, the inverted ternary data signal S2 'is "-
Only when it corresponds to “1”, the bit “1-π” having the amplitude “1” and the phase “π” is output to the multiplexer 5 as an optical signal. In the EA modulators 3 and 4, the value of the ternary data signal S2 and the inverted ternary data signal S2 'is "0".
Are also in the extinction state, and output to the multiplexer 5 as the value “0” as it is.

The multiplexer 5 multiplexes the optical signals modulated and output from the EA modulators 3 and 4 and outputs the multiplexed optical signal to the optical fiber 6. In this case, the value corresponding to "1" of the ternary data signal S2 is set to bit "1-0", and the value corresponding to "-1" of the inverted ternary data signal S2 'is set to bit "1-π". The optical duobinary signal S3 shown in FIG. 2 is combined by the multiplexer 5 because the optical output is performed without overlapping and the other signals are in the extinction state.

Although the phase shifter 11 shown in FIG. 1 is connected and arranged between the duplexer 2 and the EA modulator 4, as shown in FIG. It may be arranged to be connected between the EA modulator 4 and the multiplexer 5. This is because the phase of the optical signal output from the electrical / optical converter 1 may be inverted before reaching the multiplexer 5.

The electrical / optical converter 1, the duplexers 2, 5, the phase shifter 11, and the EA modulators 3, 4 shown in FIG. 1 are integrated and formed on the same optical integrated circuit A. You may do so. Accordingly, in addition to the use of the EA modulators 3 and 4, the reduction in size and weight of the optical transmission device can be further promoted. It should be noted that even if only some of these components are integrated on the same optical integrated circuit, the effect of reducing the size and weight can be achieved.

According to the first embodiment, an EA modulator that does not require a large driving voltage is used as an optical modulator.
Since an amplifier and a bias voltage circuit for generating a large drive voltage are not required, an optical duobinary signal can be generated by a small and lightweight optical transmitter. In addition, by integrating components for handling light on the same optical integrated circuit, the size and weight of the optical transmission device can be further reduced.

Embodiment 2 Next, a second embodiment of the present invention will be described. In the first embodiment, two Es
Although the configuration is such that the A modulators 3 and 4 are used, in the second embodiment, an optical transmitter that can be further reduced in size and weight is realized by using one EA modulator.

FIG. 5 is a block diagram showing a configuration of the optical transmission apparatus according to the second embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing signal waveforms generated by the respective units shown in FIG. In FIG. 5, a binary data signal S11 shown in FIG.
Is input to a code converter 27 constituted by a low-pass filter LPF. The code converter 27 converts the binary data signal S11 into a ternary data signal (duo-binary signal) S12 shown in FIG. 6 and outputs it to the squarer 32 and the code detector 33. This ternary data signal S12 is
This is a ternary data signal having light intensity (amplitude) of “1”, “0”, and “−1”.

The squarer 32 squares the ternary data signal S12 output from the code converter 27 to generate a squared signal S13 shown in FIG. That is, the squarer 32 outputs “1” of the ternary data signal S12,
“0” and “−1” are converted into squared signals S13 of “1”, “0” and “1”, respectively, and output to the EA modulator 23. On the other hand, the code detector 33 detects the code of the ternary data signal S12 output from the code converter 27, and keeps the phase unchanged when it is "1" and "0", and when it is "-1" , Is instructed to invert the phase.

The electric / optical converter 21 generates an optical signal corresponding to the input electric signal, and outputs the generated optical signal to the EA modulator 23. The EA modulator 23 modulates the optical signal input from the electric / optical converter 21 with the square signal S13 input from the squarer 32, and outputs the modulated signal to the phase shifter 31. Since the square signal S13 is only “1” and “0”, the optical signal modulated by the EA modulator 23 is also “1”.
And "0".

The phase shifter 31 is operated by the code detector 33 only when the ternary data signal S12 is "-1".
Inverts the phase of the optical signal output from the EA modulator 23,
The signal is output to the optical fiber 26 as an optical duobinary signal S14.

Here, the operation of the EA modulator 23 will be described with reference to FIG. In FIG. 7, the squarer 32 is
The ternary data signal S12 is converted into a square signal S13, and EA
Output to the modulator 23. The EA modulator 23 applies “1” and “−1” of the square signal S13 to “1” by applying a bias voltage of the square signal S13 in accordance with the electrical-optical conversion input / output characteristic of the EA modulator 23. And outputs “0” as “0”.

On the other hand, the sign detector 33 detects the sign of the ternary data signal S12, and the phase shifter 31 keeps the phase as "0" when the sign is "1", and keeps the phase as "0" when the sign is "1". At this time, the phase is set to “0” and the sign is “−1”.
At this time, the phase of the optical signal output from the EA modulator 23 is inverted by setting the phase to “π”, whereby the phase shifter 31
Outputs an optical duobinary signal S14.

The electric / optical converter 21 shown in FIG.
The EA modulator 23 and the phase shifter 31 may be integrated and formed on the same optical integrated circuit B. This allows
In addition to employing the EA modulator 23, the size and weight of the optical transmitter can be further reduced. It should be noted that even if only some of these components are integrated on the same optical integrated circuit, the effect of reducing the size and weight can be achieved.

According to the second embodiment, an EA modulator that does not require a large driving voltage is used as an optical modulator.
Since an amplifier and a bias voltage circuit for generating a large drive voltage are not required, and only one EA modulator 23 is used, a small and lightweight optical transmitter is realized. A duobinary signal can be generated. In addition, by integrating components for handling light on the same optical integrated circuit, the size and weight of the optical transmission device can be further reduced.

Embodiment 3 Next, a third embodiment of the present invention will be described. In the first embodiment, two Es
Although the configuration using the A modulators 3 and 4 is adopted, in the third embodiment, as in the second embodiment, an optical transmitter which can be further reduced in size and weight is realized by using one EA modulator. I have.

FIG. 8 is a block diagram showing a configuration of the optical transmission apparatus according to the third embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing signal waveforms generated by the respective units shown in FIG. 8, the binary data signal S21 shown in FIG. 9 is input to the data input terminal 49, and the binary data signal S21 shown in FIG.
Is input to a code converter 47 constituted by a low-pass filter LPF. The code converter 47 converts the binary data signal S21 into a ternary data signal (duobinary signal) S22 shown in FIG. 9 and is input to one end of the code detector 53 and the exclusive OR circuit 54. The ternary data signal S22 is a ternary data signal having light intensity (amplitude) of "1", "0", and "-1".

On the other hand, the inverted data input terminal 50 has an inverted binary data signal S2 obtained by inverting the binary data signal S21.
1 'is input, and the inverted binary data signal S21' is converted to a code converter 48 composed of a low-pass filter LPF.
Is input to The code converter 48 converts the inverted binary data signal S21 ′ into an inverted ternary data signal S21 ′ obtained by inverting the ternary data signal S22 shown in FIG. 9, and is input to the other end of the exclusive OR circuit 54. You.

The exclusive OR circuit 54 performs an exclusive OR operation on the ternary data signal S22 and the inverted ternary data signal S22 ', and outputs the operation result to the EA modulator 43. That is, since the inverted ternary data signal S22 'is an inverted version of the ternary data signal S22, the exclusive OR circuit 54
Outputs “1” when the binary data signal S22 is “1” or “−1”. As a result, the exclusive OR circuit 5
4 is output from the squarer 3 in the second embodiment.
The output is the same as that of the squared 2 signal S13.

On the other hand, the code detector 53 is provided with a code converter 47.
The sign of the ternary data signal S22 output from
When "1" and "0", the phase is left as it is,
When the value is "-1", the phase shifter 51 is operated to invert the phase.
Instruct to.

The electrical / optical converter 41 generates an optical signal corresponding to the input electrical signal, and outputs the generated optical signal to the EA modulator 43. The EA modulator 43 converts the optical signal input from the electrical / optical converter 41 into an exclusive OR circuit 54.
The signal is modulated by the output signal S23 input from the phase shifter 51 and output to the phase shifter 51. Since the output signal S23 is only “1” and “0”, the optical signal modulated by the EA modulator 43 also has the values of “1” and “0”.

The phase shifter 51 operates only when the ternary data signal S22 is "-1" according to the instruction from the code detector 53.
Invert the phase of the optical signal output from the EA modulator 43,
The optical duobinary signal S24 is output to the optical fiber 46.

Here, referring to FIG. 10, EA modulator 43
The operation of will be described. In FIG. 10, the exclusive OR circuit 54 performs an exclusive OR operation by using the ternary data signal S22 and the inverted ternary data signal S22 'as inputs.
The output signal S23 is output to the EA modulator 43. When performing an exclusive-OR operation, the threshold value SH is provided so that the bit “−” of the inverted ternary data signal S22 ′ is set.
"1" is recognized as bit "1". As a result, 3
The output signal S23 in which the bits “1” and “−1” of the value data signal S22 become the bit “1” and the bit “0” becomes the bit “0” is generated. In the EA modulator 43, E
According to the electrical-optical conversion input / output characteristics of the A modulator 43,
By applying a bias voltage to the output signal S23, the output signal S23 is modulated, and as a result, the bits “1”, “0”, and “−1” of the ternary data signal S22 become bits “1”, “1”, respectively. The light signal is output as “0” or “1”.

On the other hand, the sign detector 53 detects the sign of the ternary data signal S22, and when the sign is "1", the phase shifter 51 sets the phase to "0", does not change the phase, and changes the sign. When “0”, the phase is set to “0” and the phase is not changed. When the code is “−1”, the phase is set to “π” and the EA modulator 4 is set to “π”.
The optical duobinary signal S24 is output by inverting the phase of the optical signal output from the third optical signal generator 3.

The electric / optical converter 41 shown in FIG.
The EA modulator 43 and the phase shifter 51 may be integrated and formed on the same optical integrated circuit C. This allows
In addition to employing the EA modulator 43, the size and weight of the optical transmission device can be further reduced. It should be noted that even if only some of these components are integrated on the same optical integrated circuit, the effect of reducing the size and weight can be achieved.

The code converter 53 shown in FIG. 8 converts the ternary data signal S22 converted by the code converter 47.
When the ternary data signal S22 is "-1" based on the detection result, the phase of the optical signal of the EA modulator 43 is inverted by the phase shifter 51.
As shown in FIG. 1, the sign of the inverted data signal S22 'converted by the code converter 48 is detected, and based on this detection result, the inverted ternary data signal S22' is set to "1,"
When the value data signal S22 is “−1”, the EA modulator 43
May be inverted by the phase shifter 51. This also allows the phase shifter 51 to output the optical duobinary signal S24.

Further, as shown in FIG.
Is connected and installed between the electrical / optical converter 41 and the EA modulator 43, and the code detector 53 detects the code of the ternary data signal S22 converted by the code converter 47. Based on the detection result, the ternary data signal S2
When 2 is “−1”, before modulation by the EA modulator 43,
The phase of the optical signal output from the electrical / optical converter 41 may be inverted in advance. This also allows the EA modulator 43
Can output an optical duobinary signal S24. 11, a code detector 53 for detecting the code of the inverted ternary data signal S22 'converted by the code converter 48 is provided, and the code detector 53 has a code "1".
May be detected, the phase of the optical signal output from the electrical / optical converter 41 may be inverted by the phase shifter 52.

According to the third embodiment, an EA modulator that does not require a large driving voltage is used as an optical modulator.
Since an amplifier and a bias voltage circuit for generating a large drive voltage are not required, and only one EA modulator 23 is used, a small and lightweight optical transmitter is realized. A duobinary signal can be generated. In addition, by integrating components for handling light on the same optical integrated circuit, the size and weight of the optical transmission device can be further reduced.

[0056]

As described above, according to the present invention, the data input signal is code-converted by the first code converter, and this code converted signal is input to the first electro-absorption optical modulator. At the same time, the inverted signal of the data input signal is code-converted by the second code converter, and this code converted signal is input to the second electro-absorption optical modulator. On the other hand, electricity /
The optical signal output from the optical converter is split into two optical signals by the first optical coupler, one optical signal is input to the first electro-absorption optical modulator, and the other optical signal is shifted. After the phase is inverted by the phaser, it is input to the second electro-absorption optical modulator. The first electro-absorption optical modulator modulates the optical signal with the code conversion signal output from the first code converter, and the second electro-absorption optical modulator outputs the signal from the second code converter. The second optical coupler modulates the optical signal whose phase is inverted by the code conversion signal, and outputs the optical signal output from the first electro-absorption optical modulator and the optical signal output from the second electro-absorption optical modulator. Multiplexed optical signals and output them.Using an electro-absorption optical modulator that does not require a large driving voltage as the optical modulator, an amplifier or bias voltage circuit for generating a large driving voltage is used. Since it is not necessary, there is an effect that the configuration of the entire optical transmission device can be reduced in size and weight.

According to the next invention, the first electro-absorption type optical modulator modulates one optical signal output from the first optical coupler by the code conversion signal output from the first code converter. A second electro-absorption optical modulator modulates the other optical signal output from the first optical coupler by a code conversion signal output from the second code converter, and the phase shifter The phase of the optical signal modulated by the electro-absorption optical modulator is inverted, and the second optical coupler outputs the optical signal output from the first electro-absorption optical modulator and the optical signal output from the phase shifter. Are combined and output, and an electro-absorption type optical modulator that does not require a large driving voltage is used as the optical modulator.
Since an amplifier and a bias voltage circuit for generating a large driving voltage are not required, an effect is obtained that the configuration of the entire optical transmission device can be reduced in size and weight.

According to the next invention, the code converter performs code conversion of the data input signal, the squarer calculates and outputs the square value of the code-converted code conversion signal, and the code detector performs the code conversion. The electro-absorption optical modulator outputs a signal obtained by modulating the optical signal output from the electric / optical converter by the signal output from the squarer to the phase shifter. The phase shifter performs phase inversion of the input optical signal according to the code detected by the code detection signal and outputs the inverted signal, and as an optical modulator, electroabsorption modulation that does not require a large driving voltage. The use of a modulator eliminates the need for an amplifier or a bias voltage circuit for generating a large drive voltage, and uses only one electro-absorption optical modulator, further promoting the reduction in size and weight of the optical transmitter. With There is an effect that that.

According to the next invention, the first code converter performs code conversion of the data input signal, inputs the code converted signal to one end of the exclusive OR circuit, and performs the second code conversion. A converter performs code conversion on the inverted signal of the data input signal, inputs the code-converted code conversion signal to the other end of the exclusive OR circuit, and the exclusive OR circuit outputs the signal from the first code converter. An exclusive-OR of the output code conversion signal and the code conversion signal output from the second code converter is output and input to the electro-absorption optical modulator, and the electro-absorption optical modulator is: The optical signal output from the electrical / optical converter is modulated by the signal output from the exclusive OR circuit and output to the phase shifter, and the code detector performs the first code conversion or the second code conversion. Detects the sign of the sign conversion signal output from the The optical modulator inverts the phase of the optical signal output from the electroabsorption optical modulator in accordance with the code detected by the code detector and outputs the inverted signal. As an optical modulator, an electric field that does not require a large driving voltage is used. The use of an absorption type optical modulator eliminates the need for an amplifier and a bias voltage circuit for generating a large driving voltage, and uses only one electroabsorption type optical modulator. Is further promoted.

According to the next invention, the first code converter performs code conversion of the data input signal, inputs the code converted signal to one end of the exclusive OR circuit, A converter performs code conversion on the inverted signal of the data input signal, inputs the code-converted code conversion signal to the other end of the exclusive OR circuit, and the exclusive OR circuit outputs the signal from the first code converter. The exclusive-OR of the output code conversion signal and the code conversion signal output from the second code converter is output and input to the electro-absorption optical modulator. Detecting the sign of the code conversion signal output from the code converter or the second code converter, the phase shifter,
The optical signal output from the electrical / optical converter is inverted in phase according to the code detected by the code detector and output to the electro-absorption optical modulator. The output optical signal is modulated by the signal output from the exclusive OR circuit and output, and an electro-absorption optical modulator that does not require a large driving voltage is used as the optical modulator, and a large driving voltage is used. Since an amplifier and a bias voltage circuit for generating the signal are not required, and only one electro-absorption optical modulator is used, the size and weight of the optical transmission device can be further reduced.

According to the next invention, an electric / optical converter, a first electro-absorption type optical modulator, a second electro-absorption type optical modulator,
Since at least two of the electro-absorption optical modulator and the phase shifter are configured on the same optical integrated circuit board, and the components for handling light are integrated on the same optical integrated circuit,
In addition to eliminating the need for a configuration such as an optical connector, an optical transmission device having a highly accurate and highly stable optical device can be realized, and further, the size and weight of the optical transmission device can be further promoted.

According to the next invention, the data input signal is a binary data signal, and the code conversion signal is a ternary duobinary signal obtained by code conversion of the binary data signal. Since the optical signal output from the device is output as an optical duobinary signal including the optical phase modulation, when the optical signal output from the optical transmitter is guided through an optical fiber, the optical dispersion is reduced. This has the effect of being able to overcome the limitations of transmission distance.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical transmission device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing signal waveforms of respective units shown in FIG.

FIG. 3 is a diagram illustrating an operation of the EA modulator of the optical transmission device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a modified example of the optical transmission device according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of an optical transmission device according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating signal waveforms of respective units illustrated in FIG. 5;

FIG. 7 is a diagram illustrating an operation of an EA modulator of the optical transmission device according to the second embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of an optical transmission device according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating signal waveforms of respective units illustrated in FIG. 8;

FIG. 10 is a diagram illustrating an operation of an EA modulator of the optical transmission device according to the third embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a modified example of the optical transmitter according to the third embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of a modified example of the optical transmitting apparatus according to the third embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of a conventional optical transmission device.

FIG. 14 is a diagram illustrating signal waveforms of respective units illustrated in FIG. 13;

FIG. 15 is a diagram illustrating an operation of an LN modulator of a conventional optical transmission device.

[Explanation of symbols]

1,21,41 Electric / optical converter, 2,5 demultiplexer,
3, 4, 23, 43 EA modulator, 6, 26, 46 optical fiber, 7, 8, 27 transcoder, 9, 29, 49
Data input terminal, 10, 50 inverted data input terminal,
11, 31, 51, 52 phase shifter, 32 squarer, 3
3,53 code detector, AC optical integrated circuit, S1, S
11, S21 binary data signal, S1 ', S21' inverted binary data signal, S2, S12, S22 ternary data signal, S2 ', S22' inverted ternary data signal, S3
S14, S24 Optical duobinary signal.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // H04L 27/00 F term (reference) 2H079 AA02 AA13 BA01 CA05 DA16 FA02 KA20 5K002 AA01 AA02 BA02 BA04 BA07 CA16 DA05 FA01 5K004 AA01 BA01 BC01

Claims (7)

[Claims] A first code converter for performing code conversion on a data input signal; a second code converter for performing code conversion on an inverted signal of the data input signal; and converting an electric signal into an optical signal. An electrical / optical converter for outputting, a first optical coupler for splitting an optical signal output from the electrical / optical converter, and one of the optical signals split by the first optical coupler for the first optical coupler. A first electro-absorption optical modulator that modulates with a code conversion signal output from one code converter, and a phase shifter that inverts the phase of the other optical signal split by the first optical coupler. A second electro-absorption optical modulator that modulates an optical signal whose phase has been inverted by the phase shifter with a code conversion signal output from the second code converter; and the first electro-absorption light modulation. And the second electro-absorption optical modulator. Optical transmitter, wherein the second optical coupler and outputting the multiplexed modulated light signal, further comprising a Te. 2. The phase shifter is connected between the second electro-absorption optical modulator and the second optical coupler, and the light modulated by the second electro-absorption optical modulator. 2. The optical transmission device according to claim 1, wherein a signal phase is inverted and output to the second optical coupler. 3. A code converter for performing code conversion of a data input signal; a squarer for calculating and outputting a square value of a code conversion signal output from the code converter; and a code conversion output from the code converter. A code detector for detecting a code of a signal, an electric / optical converter for converting an electric signal into an optical signal and outputting the signal, and a signal output from the squarer for the optical signal output from the electric / optical converter. An electro-absorption type optical modulator that modulates by: a phase shifter that inverts and outputs the phase of an optical signal output from the electro-absorption type optical modulator according to the code detected by the code detector. An optical transmission device comprising: 4. A first code converter for performing code conversion on a data input signal, a second code converter for performing code conversion on an inverted signal of the data input signal, and an output from the first code converter. An exclusive OR circuit for calculating and outputting an exclusive OR of the code conversion signal to be output and the code conversion signal output from the second code converter; and the first code converter or the second code. A code detector that detects a code of a code conversion signal output from the converter, an electric / optical converter that converts an electric signal into an optical signal and outputs the same, and an optical signal that is output from the electric / optical converter. An electro-absorption optical modulator that modulates with a signal output from the exclusive-OR circuit, and a phase of an optical signal output from the electro-absorption optical modulator according to a code detected by the code detector. Invert and output phase shift An optical transmission device, comprising: 5. The phase shifter is connected between the electro-optical converter and the electro-absorption optical modulator, and the electro-optical converter is responsive to a code detected by the code detector. The optical transmission device according to claim 4, wherein the optical transmission device inverts the phase of the optical signal output from the optical modulator and outputs the inverted signal to the electro-absorption optical modulator. 6. An electro-optical converter, the first electro-absorption optical modulator, the second electro-absorption optical modulator, the electro-absorption optical modulator, and the phase shifter. The optical transmitter according to claim 1, wherein the above components are configured on the same optical integrated circuit board. 7. The light according to claim 1, wherein the data input signal is a binary data signal, and the code conversion signal is a ternary duobinary signal. Transmission device.