JP2003295137A - Light transmitting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable light transmitting circuit having a low insertion loss and a low cost. <P>SOLUTION: An optical modulation signal 17 corresponding to an input electrical signal 15 is obtained by applying frequency-divided electrical signals 21<SB>1</SB>, 21<SB>2</SB>on each electrode by using an optical modulator 1 having a plurality of electrodes 8<SB>1</SB>, 8<SB>2</SB>, a plurality of electric filters 19<SB>1</SB>, 19<SB>2</SB>having different frequency passbands and a plurality of driving circuits 21<SB>1</SB>, 21<SB>2</SB>. The range of each driving circuit can be made narrower than the conventional range. The path of the electrical signal is shorter and stabler than in the case two optical modulators having one electrode for each are used, since the use of only one optical modulator is sufficient, and also the insertion loss of the optical modulator is lower by the amount of loss for one modulator. The cost of the optical modulator 1 is lower even though a plurality of electrodes are furnished, as compared with the cost of two optical modulators having one electrode for each. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter circuit,
It is useful for generating ultra-high-speed optical signals used in optical fiber communication systems.

[0002]

2. Description of the Related Art Recent optical fiber communication systems are
Although the increase in capacity has accelerated due to the development of M (wavelength multiplex) transmission technology, the signal speed per wavelength has also increased in parallel, and 10 Gbit / s / CH (CH
Is a wavelength channel), and 40 Gbit /
s / CH system research and development is being actively conducted.

The improvement of the signal rate per wavelength is considered to be advantageous for increasing the capacity, since the frequency utilization efficiency can be improved relatively easily. In fact, most of the reports of transmission experiments in which the total capacity exceeds 3 Tbit / s use an optical transceiver circuit of 40 Gbit / s to 43 Gbit / s per wavelength.

In these experiments, a Mach-Zehnder interferometer type optical intensity modulator (hereinafter, LZ MZM) using the electro-optic effect of lithium niobate is often used for the optical intensity modulator. This is the only MZM manufactured by LN at present, which can convert an electric signal of 40 Gbit / s into an optical signal and can simultaneously control the optical phase at the time of intensity modulation of light required when applying the WDM technology. Because.

However, there is a problem in applying the MZM manufactured by LN. That is, since the voltage of the electric signal applied to the LN-made MZM is relatively high (3 to 6 Vp-p),
A high output modulator drive circuit (hereinafter, drive circuit) having a wide band frequency characteristic is required. The amplitude of the electric signal input to the drive circuit is 0.5 Vp-p to 1.0 Vp-p.
Since it is as small as p, the gain must be large. The drive circuit must meet these three requirements (wideband frequency characteristics, high output, high gain), and 40 Gbit
There are few manufacturing companies that realize the drive circuit for the / s optical transmission circuit.

The inventor has previously used a first light intensity modulator and a second light intensity modulator as means for overcoming the limitation of the operation speed by the drive circuit.
The first optical intensity modulators are connected in cascade, the input electric signal is branched into two, one of which cuts high frequency components by the LPF, and the other is amplified by a relatively narrow band baseband amplifier. Proposes a method to obtain a light intensity modulator corresponding to an input electric signal by driving the second light intensity modulator by driving the other and cutting the low frequency component by HPF and then amplifying by the high frequency amplifier. is doing.
(K. Hagimoto et al., "Ultra-High-Speed Modulation Techn
ology for IM / DD System ", MoC1.4, ECOC'93, 1993)

By using the above method, it is possible to realize a high-speed optical transmission circuit without using a wideband and high-power drive circuit.

[0008]

However, it has been found that the above-mentioned method of connecting two optical modulators in cascade has the following three problems. Therefore, it was not a practical technique. (1) The first problem is that the optical loss generated inside the optical transmission circuit is
That is twice as much as when using only one optical modulator. (2) The second problem is stability and difficulty of adjustment. In the experiment at the time of proposing the above method, two optical modulators were connected by an optical fiber of several meters, so that a coaxial code of several meters was also required for phase adjustment of the electric signal, which made adjustment difficult.
The system was not stable due to temperature fluctuation. (3) The third problem is that an increase in cost cannot be avoided because two optical modulators are used.

The present invention has been made in order to solve the above-mentioned problems, and by using an optical modulator having a plurality of electrodes, two optical modulators, which were conventionally required, are provided.
As a result, all of the above-mentioned three problems caused by using two optical modulators can be solved.

[0010]

The optical transmission circuit of the first invention comprises a light source for generating continuous light, branching means for branching an input electric signal into an integer N of 2 or more, and N electrodes. , An interferometric light intensity modulator whose interference amount changes according to the voltage of each of the electrodes, an electric filter having N different pass frequency bands, and N driving circuits. When the pass frequency bands are overlapped, the entire pass frequency band substantially includes the signal frequency band of the input electric signal, and the electric signals branched by the branching unit pass through the electric filter one by one, All of them are applied to the electrodes of the interferometric light intensity modulator via the drive circuit without passing through the electric filter, and generate a light intensity modulation signal corresponding to the input electric signal from the continuous light. Special To.

The optical transmission circuit of the second invention comprises a light source for generating continuous light, branching means for branching an input electric signal into an integer N of 2 or more, an optical phase modulator having N electrodes, and N. A plurality of electric filters having different pass frequency bands and N driving circuits are provided. When the pass frequency bands of the N electric filters are overlapped, the entire pass frequency band is equal to the signal frequency band of the input electric signal. Each of the electric signals substantially including and branched by the branching means passes through the electric filter one by one, and all of them pass through the drive circuit regardless of the front and rear of the electric filter. An optical phase modulation signal corresponding to the input electric signal is generated from the continuous light by being applied to the electrodes.

The optical transmission circuit of the third invention comprises a light source for generating continuous light, a push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator having N / 2 electrodes on each of two arms, and an input electric signal. A differential amplifier that outputs two differential electrical signals corresponding to the above, N electrical filters, and N driving circuits, where N is 2 and the pass frequency bands of the N electrical filters are overlapped. Together, the overall pass frequency band substantially comprises the signal frequency band of the input electrical signal, and the two differential electrical signals of the differential amplifier each pass through the electrical filter, all of which are of the electrical filter. The light intensity signal corresponding to the input electric signal is generated from the continuous light by being applied to the electrodes of the light intensity modulator through the drive circuit without regard to the front and rear.

An optical transmitter circuit according to a fourth aspect of the present invention has a light source for generating continuous light, one electrode of one of two arms, and an electrode of the other arm when N is an integer of 3 or more. A Mach-Zehnder interferometer type optical intensity modulator having N-1 electrodes on its arm, a differential amplifier for outputting two differential electrical signals corresponding to the input electrical signal, and two of the differential amplifiers.
Branching means for branching one of the two differential electric signals into N-1 pieces, N pieces of electric filters having different pass frequency bands, and N
When the pass frequency bands of the N electric filters are overlapped, the total pass frequency band substantially includes the signal frequency band of the input electric signal, and the difference between the two difference amplifiers of the differential amplifier is provided. The other one of the electrokinetic signals passes through the one electric filter, and one of which is provided in the one arm of the light intensity modulator via the one drive circuit without passing through the electric filter. N-1 electric signals applied to the electrodes of the above and branched into N-1 pieces by the branching means respectively pass through the remaining N-1 electric filters, all of which are before and after the electric filter. The rest N-
The light intensity signal corresponding to the input electric signal is generated from the continuous light by being applied to the N-1 electrodes on the other arm of the light intensity modulator via the one drive circuit. It is characterized by

In the optical transmission circuit of the fifth invention, when a light source for generating continuous light and M is an integer of 2 or more and N is an integer of M + 2 or more, one of two arms has M electrodes. And a Mach-Zehnder interferometric optical intensity modulator having NM electrodes on the other arm, and a differential amplifier that outputs two differential electrical signals corresponding to the input electrical signal,
First branching means for branching one of the two differential electric signals of the differential amplifier into M pieces, and second branching means for branching the other one of the two differential electric signals of the differential amplifier into NM pieces. Branching means, an electric filter having N different pass frequency bands, and N
When a plurality of driving circuits are provided and the pass frequency bands of the N electric filters are overlapped, the total pass frequency band substantially includes the signal frequency band of the input electric signal, and the first branching means makes M The electric signals branched to the respective ones pass through the M electric filters, and all of them pass through the M driving circuits before and after the electric filters to the one arm of the optical intensity modulator. The N-M electric signals applied to the M electrodes and branched into N-M pieces by the second branching means pass through the remaining NM electric filters, respectively, and all of the electric signals are passed through the electric filter. N in the other arm of the light intensity modulator via the remaining N−M driving circuits regardless of before and after the filter.
-A light intensity signal corresponding to the input electric signal is generated from the continuous light by being applied to the M electrodes.

The optical transmission circuit of the sixth invention is characterized in that, in the fifth invention, N is twice M.

An optical transmitter circuit according to a seventh invention is the optical transmitter circuit according to any one of the third invention to the sixth invention, wherein the differential amplifier is deleted.
The input electric signal and its inverted signal are replaced with two differential electric signals of the differential amplifier.

An optical transmission circuit of an eighth invention is the optical transmission circuit according to any one of the first invention to the seventh invention, wherein the N electric filters are one low-pass filter, N-2 band-pass filters and one high-pass filter. It is characterized by being a filter.

An optical transmitter circuit according to a ninth aspect of the present invention is characterized in that, in any of the first to seventh aspects, the N electric filters are one low-pass filter and N-1 band-pass filters. And

The optical transmission circuit of the tenth invention is characterized in that, in any one of the first invention to the seventh invention, the N electric filters are N-1 bandpass filters and one highpass filter. And

An optical transmission circuit of an eleventh invention is characterized in that, in any one of the first invention to the seventh invention, all the N electric filters are bandpass filters.

The optical transmission circuit of the twelfth invention is the optical transmission circuit of the first invention or the second invention, wherein N is 2 and the two electric filters are one low-pass filter and one high-pass filter. The electric filter and the branching means are realized by one frequency division circuit.

The optical transmission circuit according to the thirteenth invention is the optical transmission circuit according to any one of the first invention to the twelfth invention, wherein at least one of the N driving circuits has a gain adjusting function and an electric signal applied to each electrode. It is characterized in that the frequency amplitude of the optical transmission circuit is adjusted to flatten the frequency characteristic of the optical transmission circuit.

An optical transmission circuit of a fourteenth invention is characterized in that, in any one of the first invention to the thirteenth invention, it is provided with a phase adjustment circuit for adjusting a phase between electric signals applied to each electrode.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[Principle of the Invention] Providing two or more electrodes (electrical input ports) on an optical modulator is not so difficult with the current technology. The two-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 1 as shown in FIG. 1 has already been put to practical use. As another example, 2 shown in FIG.
Electrode Mach-Zehnder interferometric light intensity modulator 2, three-electrode Mach-Zehnder interferometric light intensity modulator 3 shown in FIG. 3, FIG.
4 electrode push-pull electrode type Mach-Zehnder interferometric optical intensity modulator 4 shown in FIG. 5, 2-electrode optical phase modulator 5 shown in FIG. 5, 6-electrode push-pull electrode type Mach-Zehnder interferometric optical intensity modulator 4 shown in FIG. There are various types such as the container 6. 1 to 6, 7 ₁ and 7 ₂ are arms (optical waveguides), 8 ₁ to
8 ₆ is an electrode (electrical input port), 9 is an optical input port, 1
Reference numeral 0 is an optical input / output port, 11 is an optical branching portion, and 12 is an optical multiplexing portion.

FIG. 7 shows the configuration of a general optical transmission circuit using the two-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 1 (hereinafter referred to as optical intensity modulator 1) shown in FIG. Indicates. The light intensity modulator 1 of FIG. 1 has electrodes 8 ₁ and 8 ₂ respectively on _two arms 7 ₁ and 7 ₂ which constitute a Mach-Zehnder interferometer. The two electrodes 8 ₁ and 8 ₂ are formed in a symmetrical arrangement.

The general optical transmission circuit shown in FIG.
Modulator 1 and light source (hereinafter, CW light source) 1 for generating continuous light
3 and two drive circuits 14₁, 14₂Composed of.
In the light intensity modulator 1, a single-ended electric data
Data signal 15 and logical inversion signal 1 of this electrical data signal 15
Enter 6. Then, continuous light is input from the CW light source 13.
Single-ended electrical data signal incident on force port 9
15 and its logic inversion signal 16
₁, 14₂Amplify with two arms 7₁ , 7₂Each
Electrode 8₁ , 8₂ Applied to the optical input port 10
An optical data signal (light intensity change) corresponding to the electrical data signal 15
Key signal) 17 is output. 18 ₁Is one electrode
8₁ Represents the electrical data signal actually applied to₂
Is the other electrode 8₂ The electrical data signal actually applied to
Represents the issue.

The electric light input / output characteristics of the light intensity modulator 1 are as follows.
It can be expressed as in equation (1).       Po = (P / 2) cos ((π / Vπ) (Vm1-Vm2 + Vo-Vb- (Vπ / 2))) + P / 2 Formula (1) Where Po is the light output power of the light intensity modulator 1 and P is the light output.
Maximum value of force, Vπ is Mach-Zehnder half-cycle voltage, Vm1
And Vm2 are two electrodes 8 of the light intensity modulator 1.₁ , 8 ₂ Mark on
The applied voltage, Vo, is the optical output when no voltage is applied.
The corresponding offset voltage, Vb, is the DC bias voltage
It

The continuous light incident on the light input port 9 of the light intensity modulator 1 is split into two by the light splitting portion 11 and propagates to the _two arms 7 ₁ and 7 ₂ . These two arms 7 ₁ , 7 ₂
In the interval, the refractive index of the optical waveguide changes depending on the voltage applied to each of the electrodes 8 ₁ and 8 ₂ , and the propagation speed of light is delayed or advanced. When the lights propagating through the _two arms 7 ₁ and 7 ₂ are combined in the optical combining unit 12, the relative optical phase changes due to the change in the refractive index, and as a result, the intensity of the combined light is increased. Changes. That is, the light intensity modulator 1 has the electrode 8
_The amount of interference changes according to the voltage applied to ₁ and 8 ₂ .
At that time, the DC bias voltage Vb is appropriately set, and the electrode 8
Electrical data signals 18 ₁ of the voltage applied to ₁ (amplitude) Vm
1 and the voltage (amplitude) Vm2 of the electrical data signal 18 ₂ applied to the electrode 8 ₂ are set in the range of −Vπ / 4 to + Vπ / 4, respectively, the optical data signal 17 output from the optical input port 10 is output. The on / off ratio of can be maximized.

In the general optical transmission circuit shown in FIG. 7, two electrical data signals 18 ₁ and 18 ₂ of the electrical data signal 15 and its logically inverted signal 16 are simultaneously transmitted to the optical intensity modulator 1.
Are adjusted to be applied to the electrodes 8 ₁ and 8 ₂ . Figure 8
The voltage Vm1 of the electrical data signal 18 ₁ applied to _one electrode 8 ₁ of the light intensity modulator ₁ , the voltage Vm2 of the electrical data signal 18 ₁ applied to the other electrode 8 ₂ of the light intensity modulator ₁ , and the light intensity modulation Power Po of the optical data signal 17 output from the device 1
Shows the relationship with.

[First Embodiment] FIG. 9 shows a light intensity modulator (two-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator) 1 shown in FIG. 1 as a first embodiment of the present invention.
An optical transmission circuit using is shown. In general optical transmitting circuit of Figure 7 described above, the electrical data signal 18 ₁ formed through the electrical data signal 15 to the drive circuit 14 _1, electrical data signal 1
The electrical data signal 18 ₂ obtained by passing the logic inversion signal 16 of No. 5 through the drive circuit 14 ₂ is directly applied to the _two electrodes 18 ₁ and 18 ₂ of the light intensity modulator 1. Then, as shown in FIG. 9, two electric filters 1
9 ₁ , 19 ₂ , for example, a low-pass filter (hereinafter, LP
F) 19 ₁ and high-pass filter (hereinafter, HPF) 19 ₂
7 is added to FIG. 7, and the electric data signal 2 having different frequency bands is added.
0 ₁ and 20 ₂ are applied to the electrodes 18 ₁ and 18 ₂ , respectively.

That is, in the first embodiment, the electric data signal 15 is passed through the drive circuit 21 ₁ and then LP
The high-frequency component is removed by F19 ₁ , while the logic inversion signal 16 becomes H after passing through the drive circuit 21 _2.
The low frequency components are removed by the PF 19 ₂ , and the electrical data signals 20 ₁ and 20 ₂ obtained respectively are applied to the electrodes 8 ₁ and 8 ₂ of the light intensity modulator 1. In this case, the optical output Po of the light intensity modulator 1 can be represented by the formula (1) above, as the passband characteristic 22 _1, 22 ₂ shown in FIG. 10, LPF 19 ₁ and HPF 19 ₂ passband If the characteristic relationships are complementary, that is, LPF19 ₁ and HPF19 _{1
When the two} pass frequency bands are overlapped, if the entire pass frequency band substantially includes the signal frequency band of the electrical data signal 15, the output optical signal is the optical data signal corresponding to the electrical data signal 15. It becomes 17. In FIG. 10, a pass band characteristic 22 ₁ of high cutoff and a pass band characteristic of low cutoff 22
₂ crosses over at a frequency of -6 dB.

The fact that the entire pass frequency band substantially includes the signal frequency band of the electric data signal 15 means that the signal frequency characteristic of the electric data signal 15 is negligible partially, for example, This means that attenuation may be given at the low-frequency end side or the high-frequency end side, and the entire pass frequency band is not necessarily the electrical data signal 1
It does not have to be above the signal frequency band of 5.

In the optical transmission circuit of FIG. 9, the drive circuit 21 ₁ ,
The characteristics required for 21 ₂ are as follows. (1) The output amplitude of the drive circuit 21 ₁ connected to the LPF 19 ₁ side is 2 of the drive circuit 14 ₁ used in the optical transmission circuit of FIG.
However, the frequency band may be about the same as that of the LPF 19 ₁ . (2) For the drive circuit 21 ₂ connected to the HPF 19 ₂ side, the gain G ₁ of the drive circuit 21 ₁ on the LPF 19 ₁ side is
It suffices to have a gain characteristic G ₂ of the same level as the above, and the frequency band may be approximately the same as the band of the HPF 19 ₂ . (3) Therefore, the requirements for the drive circuits 21 ₁ and 21 ₂ are much gentler than those of the drive circuits 14 ₁ and 14 _{2 in} FIG. (4) In addition, the electrical data signal 15 and its logic inverted signal 16 are binary, and NRZ (Non-Return-to-Zero)
If they are signals, these electrical data signals 15, 1
The high-frequency component of 6 is often smaller than the low-frequency component from the beginning. Therefore, the requirement for the maximum output amplitude characteristic of the drive circuit 21 ₂ connected to the HPF 19 ₂ is further relaxed.

By using one light intensity modulator having a plurality of electrodes and a plurality of electric filters in this way,
The band of each drive circuit has an advantage that the band can be narrower than that of the drive circuit in the general optical transmission circuit of FIG. In addition, an optical transmission circuit that adds a frequency-divided electrical signal to an optical intensity modulator having a plurality of electrodes to obtain an optical output signal corresponding to an input electrical signal uses two conventional optical modulators. Compared with the case, the electric signal path after frequency division can be shortened, which is stable, and the insertion loss of the modulator is 1
It has the advantage of being small. Further, there is an advantage that the cost of the optical modulator having a plurality of electrodes is smaller than that of two optical modulators having one electrode.

In FIG. 9, the drive circuits 21 ₁ and L
Change the connection order of PF19 ₁ before and after, or
The connection order of the drive circuit 21 ₂ and the HPF 19 ₂ may be changed before and after. Also, replacing the LPF 19 ₁ and HPF 19 _2, except for the frequency component of the low frequency by the HPF 19 ₂ for electrical data signals 15, whereas, for the logical inversion signal 16 also be excluding frequency components in the high range by LPF 19 ₁ good. Further, if the pass frequency bands of the two electric filters are overlapped, at least one of LPF 19 _{1 and} HPF 19 ₂ is satisfied as long as the condition that the entire pass frequency band substantially includes the signal frequency band of the electric data signal 15 is satisfied. May be a bandpass filter (hereinafter, BPF).

By providing at least one of the drive circuits 21 ₁ and 21 _{2 with} a gain adjusting function, the frequency characteristic of the entire optical transmission circuit can be flattened.

Further, the electrical data signal 15 is processed to generate an electrical signal.
Pole 21₁To the system or logic inversion signal 16
Pole 21₂Phase adjustment circuit for at least one of the
By arranging the paths, the electric lengths of the two systems can be made equal.
Wear. In other words, depending on the arrangement of the phase adjustment circuit, the two electrodes
8₁, 8₂Electrical data signal 20 to be applied to₁, 20₂while
The phase of can be adjusted, and the electrical length of the above two systems can be adjusted.
Between the electrical data signal 15 and its logic inverted signal 16
Phase shift, arm 7 of light intensity modulator 1₁, 7 ₂Light between
Path length deviation, electrode 8₁, 8₂Misalignment between two electric
Filter 19₁, 19₂Intensity due to phase shift between
It is possible to prevent the deterioration of the modulation performance.

[Second Embodiment] FIG. 11 shows, as a second embodiment of the present invention, a concrete embodiment of the optical transmission circuit of the first embodiment (FIG. 9) described above.

The optical transmission circuit of FIG. 11 includes a light intensity modulator (two-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator) 1 shown in FIG. 2 electrical filters (LPF and HPF) 1
9 ₁ , 19 ₂ and two drive circuits 21 ₁ , 21 ₂ and 2
This is provided with one gain adjusting circuit 24 ₁ and 24 ₂ and one phase adjusting circuit 25 ₁ . In addition to these, the base material 2
3, a bias applying circuit 26, an optical amplifier circuit 27, two electric input terminals 28 ₁ and 28 _2, and an optical output terminal 29 are further provided. Although not shown in FIG. 11, the optical intensity modulator 1 has two arms 7 ₁ as shown in FIG.
Electrodes 8 ₁ and 8 ₂ are formed one by one in a symmetrical arrangement with respect to 7 ₂ .

Electric input terminal 28 ₁ , drive circuit 21 ₁ , L
The PF 19 ₁ and the electrode 8 ₁ are electrically connected in this order. In addition, the electric input terminal 28 ₂ , the drive circuit 21 ₂ ,
The HPF 19 ₂ , the phase adjustment circuit 28 ₁ and the electrode 8 ₂ are electrically connected in this order. Furthermore, CW light source 1
3, the optical intensity modulator 1, the optical amplifier circuit 27, and the optical output terminal 29 are optically connected in this order. The gain adjusting circuits 24 ₁ and 24 ₂ are provided in the driving circuits 21 ₁ and 21 ₂ , respectively. The bias applying circuit 26 is the light intensity modulator 1.
Is connected to a bias electrode (not shown).

Continuous light from the CW light source 13 is input to the light intensity modulator 1, and the optical data signal 17 of the light intensity modulator 1 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27. The optical amplifier 27 is used to increase the transmission output of the optical transmission circuit, and is unnecessary when the optical output may be small.

The electrical data signal 15 and its logic inverted signal 16 are input to the _two electrical input terminals 28 ₁ and 28 ₂ . The electrical data signal 15 input from _one electrical input terminal 28 ₁ is amplified by the drive circuit 21 ₁ and then the LPF 1
High frequency components are cut off by 9 ₁ . The electrical data signal 20 ₁ from which the high frequency components are cut off is the optical intensity modulator 1
Is applied to _one electrode 8 ₁ . Drive circuit 21 ₁ and LP
The order of F19 ₁ does not matter before or after, and the order can be reversed. The logic inversion signal 16 input from the other electric input terminal 28 ₂ is amplified by the drive circuit 21 ₂ and then the HPF
The low frequency component is cut off by 19 ₂ and the phase is adjusted by the phase adjusting circuit 25 ₁ . The electrical data signal 20 ₂ whose low frequency component is blocked and whose phase is adjusted is applied to the other electrode 8 ₂ of the light intensity modulator 1. The order of the drive circuit 21 ₂ , the HPF 19 ₂ and the phase adjusting circuit 25 ₁ does not matter before or after, and they may be interchanged.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And HPF19₂When
The relationship with the total passband characteristics of
The passing frequency band when the electric data signal 15 (or
Is the signal frequency band of the logically inverted signal 16)
The pass band characteristic 22 shown in FIG.
₁, 22₂Is set to.

The two gain control circuits 24 _1, 24 ₂ are those respectively to independently adjustable gain G _1, G ₂ of the drive circuits 21 _1, 21 _2, thereby the whole optical transmission circuit frequency It is adjusted so that the characteristics become flat. Only _{one of} the gain adjusting circuits 24 ₁ and 24 ₂ may be used.
If the frequency characteristic becomes flat from the beginning without adjusting the gain, the gain adjusting circuits 24 ₁ and 24 ₂ are unnecessary.

The phase adjusting circuit 25 ₁ has two electrodes 8 ₁ and 8 ₁ .
It is used to adjust the phase between the electrical data signals 20 ₁ and 20 ₂ applied to the ₂ and the electrical length from the electrical input terminal 28 ₁ to the electrode 8 ₁ of the optical intensity modulator 1 and the electrical input terminal 28 2. The electrical length from ₂ to the electrode 8 ₂ of the light intensity modulator 1 is adjusted by the phase adjustment circuit 25 ₁ so that the electrical length is equal to each other. If from the beginning without using the phase adjusting circuit 25 ₁ of the same length, the phase adjustment circuit 25 ₁ is not required. In this case, it is premised that the phase relationship between the electrical data signal 15 input from the electrical input terminals 28 ₁ and 28 ₂ and its logic inverted signal 16 does not change and is always constant.

The bias applying circuit 26 sets an appropriate bias voltage (see Vb in the equation (1)) to the light intensity modulator 1, and the amplitude of the optical data signal 17 output from the light intensity modulator 1 is Bias application circuit 26
Applies a bias voltage. Bias applying circuit 2
Even if 6 is not used, if the amplitude of the optical data signal 17 is maximized from the beginning, if it is sufficiently large, the bias applying circuit 26
Is unnecessary.

[Third Embodiment] FIG. 12 shows, as a third embodiment of the present invention, the optical intensity modulator shown in FIG. 1 (two-electrode push-pull electrode type Mach-Zehnder interferometric optical intensity modulator).
2 shows another optical transmission circuit using 1. Although both the electrical data signal 15 and its logic inverted signal 16 are input in the optical transmission circuits of the first embodiment (FIG. 9) and the second embodiment (FIG. 11) described above, in the third embodiment, as shown in FIG. As shown in FIG. 12, a differential amplifier circuit 30 is added to the optical transmission circuit of the first embodiment so that only one of the single end signals is input.

In the optical transmission circuit of FIG. 12, by inputting the electric data signal (input electric signal) 15 to the differential amplifier circuit 30, two differential electric signals 31 ₁ , 31 ₂ corresponding to the electric data signal 15 are input. To generate one of the differential electrical signals 31 ₁
LPF19 After passing through the driving circuit 21 ₁ for ₁
The frequency component in the high frequency range is removed by, and the other differential electric signal 31 ₂ is obtained in each by removing the low frequency component by the HPF 19 ₂ after passing through the phase adjusting circuit 25 ₁ and the drive circuit 21 _2. Electrical data signal 2
0 ₁ and 20 ₂ are applied to the electrodes 8 ₁ and 8 ₂ of the light intensity modulator 1. For example, the differential electric signal 31 ₁ is a signal having the same phase as the input electric data signal 15, and the differential electric signal 31 ₂ is a signal whose phase is inverted with respect to the electric data signal 15.

Also in the third embodiment, the first and second embodiments are performed.
As in the example, the drive circuit 21₁And LPF19₁Connection order
Front and rear, or drive circuit 21₂And HPF
19 ₂The connection order of may be changed before and after. Also, L
PF19₁And HPF19₂Can be replaced. further,
Superimpose the pass frequency bands of two electrical filters
And the entire pass frequency band is the electrical data signal 15 signal
The condition that it is above or substantially above the frequency band
LPF 19₁Or HPF19 ₂Nou
At least one of them may be the BPF.

Further, as in the first and second embodiments, FIG.
In addition, the drive circuit 21₁, 21₂To at least one of
By providing a gain adjustment function, the frequency of the entire optical transmission circuit
The number characteristic can be flattened. In addition, the phase adjustment
Road 25₁Is one of the differential electrical signals 31₁System that processes
Or the other one of the differential electrical signals 31₂For processing
At least one of the
And two electrodes 8₁, 8 ₂Electrical data actually applied to
Signal 20₁, 20₂Light intensity modulation performance by adjusting the phase between
To improve the electrode 8 from the input of the differential vibrating device 30.₁
To the electrode 8 from the electrical length and the input of the differential viscera 30₂To
Is equal to the electrical length.

[Fourth Embodiment] FIG. 13 shows, as a fourth embodiment, an embodiment of the optical transmission circuit of the third embodiment (FIG. 12) described above.

The optical transmission circuit shown in FIG. 13 includes a light intensity modulator (two-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator) 1 shown in FIG. 2 electrical filters (LPF and HPF) 1
9 ₁ , 19 ₂ and two drive circuits 21 ₁ , 21 ₂ and 2
Individual gain adjusting circuits 24 ₁ and 24 ₂ and a phase adjusting circuit 25.
₁ and a differential amplifier 30. In addition to these, a bias applying circuit 26 is further provided on the base material 23.
And an optical amplifier circuit 27, one electric input terminal 28 ₁ and an optical output terminal 29. Although not shown in FIG. 13, the light intensity modulator 1 has electrodes 8 ₁ and 8 ₂ formed on the two arms 7 ₁ and 7 ₂ in a symmetrical arrangement as shown in FIG. .

In FIG. 13, one electric input terminal 28
₁ input terminal of the differential amplifier circuit 30 is electrically connected to the drive circuit to one output terminal of the differential amplifier circuit 30 21 _1, LP
F19 ₁ and electrode 8 ₁ are electrically connected in this order,
The drive circuit 21 ₂ , HPF 19 ₂ , phase adjustment circuit 25 ₁ and electrode 8 ₂ are electrically connected in this order to the other output terminal of the differential amplifier circuit 30. Furthermore, CW
The light source 13, the light intensity modulator 1, the light amplification circuit 27, and the light output terminal 29 are optically connected in this order. The gain adjusting circuits 24 ₁ and 24 ₂ are driving circuits 21 ₁ and 21 respectively.
_It is provided in ₂ . The bias applying circuit 26 is connected to the bias electrode (not shown) of the light intensity modulator 1.

Continuous light from the CW light source 13 is input to the light intensity modulator 1, and the optical data signal 17 of the light intensity modulator 1 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27. The optical amplifier 27 is used to increase the transmission output of the optical transmission circuit, and is unnecessary when the optical output may be small.

A single end electrical data signal 15 is input to the electrical input terminal 28 ₁ . Electric input terminal 28 ₁
From the electrical data signal 15 input to the differential amplifier circuit 30
Produces two differential electrical signals 31 ₁ , 31 ₂ corresponding to electrical data signal 15. Of the outputs of the differential amplifier 30, one of the differential electric signals 31 ₁ is supplied to the drive circuit 21.
After being amplified by _1, the high frequency components are cut off by the LPF 19 _1. The electrical data signal 20 ₁ in which the high frequency components are blocked is applied to the electrode 8 ₁ of the light intensity modulator 1.
The order of the drive circuit 21 ₁ and the LPF 19 ₁ does not matter before or after, and may be reversed. The other one of the differential electrical signals 31
₂ is amplified by the drive circuit 21 _2, low frequency components are cut off by the HPF 19 _2, is phase adjusted by the phase adjusting circuit 25 _1. The electrical data signal 20 ₂ whose low frequency components are blocked and whose phase is adjusted is applied to the electrode 8 ₂ of the optical intensity modulator 1. Drive circuit 21 ₂ , HPF
The order of 19 ₂ and the phase adjustment circuit 25 ₁ does not matter before and after, and they may be interchanged.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And HPF19₂When
The relationship with the total passband characteristics of
The passing frequency band when the electric data signal 15 (or
Is the signal frequency band of the logically inverted signal 16)
The pass band characteristic 22 shown in FIG.
₁, 22₂Is set to.

[0058] gain control circuit 24 _1, 24 ₂ is one that enables independently adjusted gain G _1, G ₂ of the drive circuits 21 _1, 21 _2, thereby flat frequency characteristic of the entire optical transmission circuit Has been adjusted to Gain adjustment circuit 24
₁ , 24 ₂ may be only _one , and if the frequency characteristic becomes flat from the beginning without gain adjustment,
The gain adjusting circuits 24 ₁ and 24 ₂ are unnecessary.

Phase adjusting circuit 25₁Has two electrodes 8₁, 8
₂To adjust the phase between the electrical data signals applied to
It is used and the electric input terminal 28₁From the light intensity modulator
One electrode 8₁Electrical length up to and electrical input terminal 27₁From
Electrode 8 of light intensity modulator 1₂Electrical length up to is isometric
Phase adjustment circuit 25₁Adjusted by. Phase adjustment
Circuit 25₁Even if you don't use
For example, the phase adjustment circuit 25 ₁Is unnecessary.

The bias applying circuit 26 sets an appropriate bias voltage (see Vb in the equation (1)) for the light intensity modulator 1, and the amplitude of the optical data signal 17 output from the light intensity modulator 1 is Bias application circuit 26
Applies a bias voltage. Bias applying circuit 2
If the amplitude of the optical data signal 17 is maximized from the beginning without using 6, the bias applying circuit 26 is unnecessary.

In the optical transmission circuits of the first embodiment (FIG. 9), the second embodiment (FIG. 11), the third embodiment (FIG. 12) and the fourth embodiment (FIG. 13) described above, the two-electrode push is used. Although the pull electrode type Mach-Zehnder interferometer type optical intensity modulator 1 is used, the Mach-Zehnder interferometer type optical device having two or more electrodes in each of the _two arms 7 ₁ and 7 ₂ regardless of whether the push-pull electrode type or not. The same structure can be used when the intensity modulator is used. For example, when using the four-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 4 shown in FIG. 4, one of the electrodes 8 ₁ and 8 ₃ of _one arm is selected and one of them is selected. Electrical data signal 20 ₁
Of the electrodes 8 ₂ and 8 ₄ of the other arm,
Any one can be selected and configured to apply the other electrical data signal 20 ₂ . This is 6
It can be extended and applied to the case of using a push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator having electrodes or more. For example, when using the 6-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 6 shown in FIG. 6, any _one of the electrodes 8 ₁ , 8 ₃ and 8 ₅ of one arm is selected. So as to apply _one electric data signal 20 ₁ and select any one of the electrodes 8 ₂ , 8 ₄ and 8 ₆ of the other arm to apply the other electric data signal 20 _2. Can be configured to. These are equivalent to the first to fourth embodiments.

[Fifth Embodiment] Next, referring to FIG. 14, as a fifth embodiment of the present invention, the two-electrode Mach-Zehnder interferometer type optical intensity modulator 2 (hereinafter referred to as the optical intensity modulator 2) shown in FIG. The configuration of an optical transmission circuit using In this light intensity modulator 2, two electrodes 8 ₁ and 8 ₂ are provided on one side of _two arms 7 ₁ and 7 ₂ of the Mach-Zehnder interferometer type light intensity modulator so as to be displaced in the light traveling direction. The positions of the electrodes 8 ₁ and 8 ₂ are different from those of the push-pull electrode type Mach-Zehnder interferometric light intensity modulator 1 of the electrodes, but the operation principle of the light intensity modulation is the same. 9 is an optical input port, 10
Is an optical output port, 11 is an optical branching unit, and 12 is an optical multiplexing unit.

The optical transmission circuit of the fifth embodiment may have a single end input, and the optical intensity modulator 2 and C for generating continuous light.
W light source 13 and two electric filters (LPF and HP
F) Circuits 21 ₁ and 21 ₂ and two drive circuits 21 ₁ and 2
1 ₂ , a phase adjustment circuit 25 ₁ and a two-branch circuit 32 ₁ .

In FIG. 14, the single-ended electrical data is
Data signal (input electric signal) 15 into two branch circuits 32₁Enter
Force, two single-ended electrical data signals
33 ₁, 33₂To generate one electrical data signal 33₁
For drive circuit 21₁After passing through LPF19₁
Except for high frequency components, the other electrical data
Signal 33₂For the phase adjustment circuit 25₁And drive times
Road 21₂After passing through HPF19₂Due to low frequencies
Electrical data signal obtained by removing several components
20₁, 20₂The electrode 8 of the light intensity modulator 1₁, 8₂Mark on
Add

Thus, the two arms 7₁, 7₂Piece of
A plurality of electrodes 8 provided there even if only on the side
₁, 8₂Electrical data signal 20 with frequency band divided into₁,
20 ₂To the electrical data signal 15 by applying
A corresponding optical data signal (light intensity modulation signal) 17 is obtained.
It In addition, the drive circuit 21₁, 21₂Frequency required for
Bandwidth characteristics of the general optical transmission circuit shown in FIG.
Drive circuit 14₁, 14₂Compared to, it requires a narrower band.

Also in FIG. 14, the drive circuit 21 ₁ and LP
The connection order of F19 ₁ may be changed before and after, or the connection order of the drive circuit 21 ₂ and HPF 19 ₂ may be changed before and after. Further, the LPF 19 ₁ and the HPF 19 ₂ may be exchanged. Further, if the pass frequency bands of the two electric filters are overlapped, the LPF 19 ₁ or HPF 19 ₂ of the LPF 19 ₁ or HPF 19 ₂ is satisfied as long as the condition that the whole pass frequency band is equal to or more than the signal frequency band of the electric data signal 15 or substantially includes it. At least one of them may be the BPF. Further, by providing at least one of the drive circuits 21 ₁ and 21 _{2 with} a gain adjusting function, it is possible to flatten the frequency characteristic of the entire optical transmission circuit.

The phase adjusting circuit 25 ₁ is provided at an arbitrary position in at least one of a system that processes _one branched electrical data signal 33 ₁ and a system that processes another branched electrical data signal 33 _2. Therefore, the two electrodes 8 ₁ , 8
_The electrical length from the input of the two-branching circuit 32 ₁ to the electrode 8 ₁ and the two-branching circuit are adjusted so that the phase between the electrical data signals 20 ₁ and 20 ₂ actually applied to ₂ is adjusted to improve the light intensity modulation performance. The electrical length from the input of 32 ₁ to the electrode 8 ₂ is made equal.

[Sixth Embodiment] FIG. 15 shows a concrete embodiment of the optical transmission circuit of the fifth embodiment (FIG. 14) described above as a sixth embodiment.

The optical transmission circuit shown in FIG. 15 has a light intensity modulator (two-electrode Mach-Zehnder interferometric light intensity modulator) 2 shown in FIG. Filters (LPF and HPF) 19 ₁ and 19 ₂ , two drive circuits 21 ₁ and 21 ₂ , and two gain adjustment circuits 24
₁ , 24 ₂ , a phase adjusting circuit 25 _1, and a 2-branching circuit 32
_It is equipped with ₁ . In addition to these, a bias applying circuit 26 and an optical amplifier circuit 27 are further provided on the base material 23.
And an electric input terminal 28 ₁ and a light output terminal 29. Although not shown in FIG. 15, the light intensity modulator 2 has two electrodes 8 ₁ and 8 ₂ formed on only one of the _two arms 7 ₁ and 7 ₂ as shown in FIG.

In FIG. 15, the electric input terminal 28₁To
2-branch circuit 32₁The input end of the is electrically connected to two branches
Circuit 32₁The drive circuit 21 is provided at one output end of the₁, LPF1
9₁And electrode 8₁Are electrically connected in this order, and
2 branch circuit 32₁Drive circuit 2 at the other output end
1₂, HPF19₂, Phase adjustment circuit 25₁And electrode 8
₂Are electrically connected in this order. Furthermore, CW light
Source 13, light intensity modulator 1, light amplification circuit 27 and light output
The terminals 29 are optically connected in this order. Gain adjustment
Circuit 24₁, 24₂Are drive circuits 21₁, 21₂
It is provided in. The bias applying circuit 26 modulates the light intensity
Connected to a bias electrode (not shown) of the container 2.

Continuous light from the CW light source 13 is input to the light intensity modulator 2, and the optical data signal 17 of the light intensity modulator 2 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27. The optical amplifier 27 is used to increase the transmission output of the optical transmission circuit, and is unnecessary when the optical output may be small.

Electric input terminal 28₁Has a single-ended
The electrical data signal 15 is input. Electric input terminal 28₁
From the electrical data signal 15 inputted from the two branch circuit 32
₁Two electrical data corresponding to electrical data signal 15
Data signal 32₁, 32₂Is branched. 2-branch circuit 32
₁One of the signals branched by the electrical data signal 33 ₁
Is the drive circuit 21₁LPF19 after being amplified by₁By
High frequency components are cut off. High frequency components cut off
Electrical data signal 20₁Is the electrode 8 of the light intensity modulator 2
₁Applied to. Drive circuit 21₁And LPF19₁The order of
Can be before or after, and vice versa. The other one
Qi data signal 33₂Is the drive circuit 21₂Amplified in
After that, HPF19₂Low frequency components are blocked by
Phase adjustment circuit 25₁The phase is adjusted by. Low frequency composition
Minute electrical signal 2 with phase cut and phase adjusted
0₂Is the electrode 8 of the light intensity modulator 2₂Applied to. Drive times
Road 21₂, HPF19₂And phase adjustment circuit 25₁Order of
The order does not matter before and after, and it can be replaced.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And HPF19₂When
The relationship with the total passband characteristics of
The passing frequency band when the electric data signal 15 (or
Is the signal frequency band of the logically inverted signal 16)
The pass band characteristic 22 shown in FIG.
₁, 22₂Is set to. At that time, the gain adjustment circuit 2
Four₁, 24₂The frequency characteristics of the entire optical transmission circuit
Adjusted to be flat. Gain adjustment circuit 24₁Two
Four₂Is each drive circuit 21₁, 21₂Gain G₁, G₂The German
It is possible to adjust vertically, but only one side is enough,
In other words, the frequency response will be flat from the beginning without adjustment.
If so, the gain adjustment circuit 24₁, 24₂Is unnecessary
It

Phase adjusting circuit 25₁Has two electrodes 8₁, 8
₂To adjust the phase between the electrical data signals applied to
It is used and the two-branch circuit 32₁Two forked with
Electrical data signal 33₁, 33₂Electrical input out of the path
Terminal 28₁From the electrode 8 of the light intensity modulator 2₁Electrical length up to
And the electric input terminal 28₁From the electrode 8 of the light intensity modulator 2 ₂
Phase adjustment circuit 25 so that the electrical length up to₁To
More adjusted. Phase adjustment circuit 25₁Without using
If the lengths are equal, the phase adjustment circuit 25₁Is not
It is important.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 2, and the bias applying circuit 26 is set so that the amplitude of the optical data signal 17 output from the light intensity modulator 2 becomes maximum. Applies a bias voltage. Even if the bias applying circuit 26 is not used, if the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning,
The bias applying circuit 26 is unnecessary.

[Seventh Embodiment] FIG. 16 shows the LPF in the sixth embodiment (FIG. 15) described above as the seventh embodiment of the present invention.
19 shows the configuration of an optical transmission circuit in which 19 ₁ , HPF 19 ₂ and two branch circuits 32 ₁ are integrated into one circuit.

[0077] Light transmission circuit of Figure 16 is, LPF 19 _1, HPF 19 ₂ and 2 branch circuit 3 in the optical transmitter circuit of Figure 15
Instead of 2 ₁ , one frequency division circuit 34 is used. The frequency dividing circuit 34 is a circuit that separates an electric signal input to the input port into a low frequency component and a high frequency component, and outputs each to the first output port and the second output port.

That is, the optical transmitter circuit shown in FIG.
The optical intensity modulator (two-electrode Mach-Zehnder interferometric optical intensity modulator) 2 shown in FIG. 2, a CW light source 13, two drive circuits 21 ₁ and 21 ₂ , and two gain adjusting circuits are shown above. 24
₁ , 24 ₂ , a phase adjusting circuit 25 ₁ and a frequency dividing circuit 34 are provided. In addition to these, a bias applying circuit 26 and an optical amplifier circuit 27 are further provided on the base material 23.
And an electric input terminal 28 ₁ and an optical output terminal 29.

In FIG. 16, the input port of the frequency division circuit 34 is electrically connected to the electric input terminal 28 ₁ , the drive circuit 21 ₁ and the electrode 8 ₁ are electrically connected to the first output port in this order, and , The drive circuit 21 ₂ , the phase adjustment circuit 25 ₁ and the electrode 8 ₂ are electrically connected to the second output port in this order. Further, the CW light source 13, the light intensity modulator 1, the light amplification circuit 27, and the light output terminal 29 are optically connected in this order. Gain adjusting circuit 24 ₁ ,
24 ₂ is provided in each of the drive circuits 21 ₁ and 21 ₂ . The bias applying circuit 26 is connected to the bias electrode (not shown) of the light intensity modulator 2.

Continuous light from the CW light source 13 is input to the light intensity modulator 2, and the optical data signal 17 of the light intensity modulator 2 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27. The optical amplifier 27 is used to increase the transmission output of the optical transmission circuit, and is unnecessary when the optical output may be small.

The single-ended electrical data signal 15 is input to the input port of the frequency division circuit 34 from the electrical input terminal 28 ₁ . The electric data signal 35 ₁ in which the high frequency components of the electric data signal 15 are cut off is output from the first output port of the frequency division circuit 34, amplified by the drive circuit 21 ₁ , and then the light intensity as the electric data signal 20 _1. Modulator 2
Applied to the electrode 8 ₁ of. On the other hand, the second output port of the frequency division circuit 34 outputs the electric data signal 35 ₂ in which the low-frequency components of the electric data signal 15 are cut off, is amplified by the drive circuit 21 ₂ , and is output by the phase adjustment circuit 25 _1. After the phase adjustment, it is applied to the electrode 8 ₂ of the light intensity modulator ₂ as an electric data signal 20 ₂ .

The relationship between the pass band characteristic of the high frequency cutoff side (first output port side) and the pass band characteristic of the low frequency image side (second output port side) of the frequency division circuit 34 is obtained by superposing the two. The pass band characteristics 22 ₁ and 22 ₂ shown in FIG. 10 are set so that the pass frequency band at that time substantially includes the signal frequency band of the electrical data signal 15. At that time, the gain adjusting circuits 24 ₁ and 24 ₂ adjust the frequency characteristics of the entire optical transmitting circuit to be flat. Gain control circuit 24 _1, 24 ₂ may be only one but is intended to independently adjustable gain G _1, G ₂ of the drive circuits 21 _1, 21 _2, or frequency from the beginning without adjustment If the characteristics are flat, the gain adjustment circuit 2
4 ₁ and 24 ₂ are unnecessary.

The phase adjusting circuit 25 ₁ has two electrodes 8 ₁ and 8 ₁ .
Are used to adjust the phase between the electrical data signals applied to the _2, of the two electrical data signals 35 _1, 35 ₂ of the route that is frequency divided by the frequency division circuit 34,
And the electrical length from the electrical input terminals 28 ₁ to the electrode ₈₁ of the light intensity modulator 2, phase adjustment circuit such that the electrical length from the electrical input terminals 28 ₁ to the electrode ₈₂ of the light intensity modulator 2 becomes equal length Adjusted by 25 ₁ . If the same length is obtained from the beginning without using the phase adjusting circuit 25 ₁ , the phase adjusting circuit 2
5 ₁ is unnecessary.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 2, and the bias applying circuit 26 is set so that the amplitude of the optical data signal 17 output from the light intensity modulator 2 becomes maximum. Applies a bias voltage. Even if the bias applying circuit 26 is not used, if the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning,
The bias applying circuit 26 is unnecessary.

17A and 17B, the frequency division circuit 3
4 shows an example of implementation. In the example shown in FIG. 17A, the frequency division circuit 34 is composed of a capacitor C and an inductor L, and the input port 34a has a capacitor C and an inductor L.
One end side of each is commonly connected. The opposite side of the inductor L serves as the first output port 34b, and the opposite side of the capacitor C serves as the second output port 34c.

The pass band characteristic of the frequency division circuit 34 composed of the capacitor C and the inductor L is as shown in FIG. 17B, and the input port 34a to the first output port 34 are used.
The pass band characteristic 36 ₁ to b is the low pass characteristic, and the pass band characteristic 36 ₁ from the input port 34a to the second output port 34c is
₂ is the high-pass characteristic.

[Eighth Embodiment] FIG. 18 shows, as an eighth embodiment of the present invention, the three-electrode Mach-Zehnder interferometer type optical intensity modulator 3 (hereinafter referred to as the optical intensity modulator 3) shown in FIG. The structure of the used optical transmission circuit is shown.

In the optical transmission circuits of the fifth to seventh embodiments described above, the Mach-Zehnder interferometer type optical intensity modulator 2 having the _two electrodes 8 ₁ and 8 ₂ on one arm is used, but this is expanded. Therefore, even if the Mach-Zehnder interferometer type optical intensity modulator has three or more electrodes on only one arm, the same number of driving circuits and electric filters can be obtained by increasing the number of driving circuits and electric filters according to the number of electrodes. Can be configured to. In addition, the four-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 4 shown in FIG.
Of the two arms of the push-pull electrode type Mach-Zehnder interferometric light intensity modulator having four or more electrodes, such as the push-pull electrode type Mach-Zehnder interferometric light intensity modulator 6 of the electrodes, only one of the two electrodes (see, for example, FIG. 4 only the two electrodes 8 ₁ , 8 _{3 of the} arm 7 ₁ or only the two electrodes 8 ₂ , 8 _{4 of the} arm 7 ₂ and in FIG. 6 only the three electrodes 8 ₁ , 8 ₃ , 8 _{5 of the} arm 7 ₁ or Using only the three electrodes 8 ₂ , 8 ₄ , 8 _{6 of the} arm 7 ₂ ) is equivalent to the above expansion, and the number of drive circuits and electric filters is increased according to the number of electrodes of one arm. By doing so, the optical transmission circuit can be similarly configured.

The optical transmission circuit shown in FIG.
The light intensity modulator 3 shown in FIG. 3, the CW light source 13, and the three
Electrical filter (LPF, BPF and HPF) 19₁,
19 ₂, 19₃And three drive circuits 21₁, 21₂Two
1₃And two phase adjustment circuits 25₁, 25₂And 3 branches
Circuit 37₁It is equipped with. In addition to these, the base material
23, a bias applying circuit 26 and an optical amplifier circuit 27 are provided.
And one electric input terminal 28₁And an optical output terminal 29
I am. Although not shown in FIG. 18, the light intensity modulator 3
Two arms 7 as shown in FIG.₁, 7₂Only one of
3 electrodes on 8 ₁, 8₂, 8₃Are formed. Na
The gain adjustment circuit is omitted.

In FIG. 18, the input end of the three-branch circuit 37 ₁ is electrically connected to the electric input terminal 28 ₁ , and the drive circuit is connected to the _first output end of the three output ends of the three-branch circuit 37 _1. 21 ₁ , LPF 19 ₁ and electrode 8 ₁ are electrically connected in this order, and the drive circuit 2 is connected to the second output end.
1 ₂ , BPF 19 ₂ , phase adjustment circuit 25 ₁ and electrode 8
₂ is electrically connected in this order, and further a third output terminal to the driving circuit 21 _{3 3} HPF 19 _3, the phase adjustment circuit 25 ₂ and the electrode 8 ₃ electrically connected in this order. Further, the CW light source 13, the light intensity modulator 1, the light amplification circuit 27, and the light output terminal 29 are optically connected in this order. The bias applying circuit 26 is connected to the bias electrode (not shown) of the light intensity modulator 3.

Continuous light from the CW light source 13 is input to the light intensity modulator 2, and the optical data signal 17 of the light intensity modulator 2 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27.

A single end electrical data signal 15 is input to the electrical input terminal 28 ₁ . Electric input terminal 28 ₁
From the electrical data signal 15 input from the three branch circuit 37
_{The 1} branches the _three electrical data signals 38 ₁ , 38 ₂ , 38 ₃ corresponding to the electrical data signal 15. Of the signals branched by the three-branch circuit 37 ₁ , the first electrical data signal 38 ₁ is amplified by the drive circuit 21 ₁ , and then the LPF 1
9 ₁ blocks the middle frequency component and the high frequency component. The electric data signal 20 ₁ in which the middle frequency component and the high frequency component are blocked is applied to the electrode 8 ₁ of the light intensity modulator 3. The order of the drive circuit 21 ₁ and the LPF 19 ₁ does not matter before or after, and may be reversed. Second electrical data signal 3
8 ₂ is amplified by the drive circuit 21 ₂ and then BPF 19 ₂
The low-frequency component and the high-frequency component are blocked by, and the phase is adjusted by the phase adjusting circuit 25 ₁ . The low-frequency component and the high-frequency component are blocked, and the phase-adjusted electrical data signal 20 ₂ is applied to the electrode 8 ₂ of the light intensity modulator 3. The order of the drive circuit 21 ₂ , the BPF 19 ₂ and the phase adjusting circuit 25 ₁ does not matter before or after, and they may be interchanged. In addition, the third electrical data signal 38
₃ is amplified by the drive circuit 21 _3, low frequency components and the middle frequency component is cut off by the HPF 19 _3, is phase adjusted by the phase adjusting circuit 25 _2. The low frequency component and the mid frequency component are blocked, and the phase-adjusted electrical data signal 20 ₃ is applied to the electrode 8 ₃ of the light intensity modulator 3. The order of the drive circuit 21 ₃ , the HPF 19 ₃ and the phase adjustment circuit 25 ₂ does not matter before and after, and they may be interchanged.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And BPF19₂When
Total pass band characteristics of the drive circuit 21₃And HPF
19 ₃The relationship with the total passband characteristics is
Electrical data signal 1 is the pass frequency band when superposed
1 to substantially include the signal frequency band of FIG.
Passband characteristics 39 shown in 9₁, 39₂, 39₃Set to
Has been done. At that time, a gain adjustment circuit (not shown)
Adjust so that the frequency characteristics of the entire optical transmitter circuit become flat.
Be adjusted. Furthermore, the pass frequencies of the three electrical filters
When the bands are overlapped, the overall pass frequency band is
Condition that signal frequency band of electrical data signal 15 is included
LPF 19₁Or HPF19₃Nou
At least one of them may be the BPF.

The phase adjusting circuits 25 ₁ and 25 ₂ are used to adjust the phase between the electric data signals applied to the _three electrodes 8 ₁ , 8 ₂ and 8 ₃ and are branched by the 3-branching circuit 37 _1. 3 electrical data signals 38 ₁ , 38 ₂ , 38 ₃
Of the optical intensity modulator 3 from the electric input terminal 28 ₁
An electric length to the electrode _81, the electrical length from the electrical input terminal 28 ₁ and the electrical length from the electrode ₈₂ of the light intensity modulator 3, from the electrical input terminals 28 ₁ to the electrode 8 ₃ of the light intensity modulator 3 Phase adjustment circuits 25 ₁ and 25 ₂ adjust so that and become equal in length. If the length is equal from the beginning, the phase adjusting circuit is not necessary.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 3, and the bias applying circuit 26 is designed to maximize the amplitude of the optical data signal 17 output from the light intensity modulator 3. Applies a bias voltage. Even if the bias applying circuit 26 is not used, if the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning,
The bias applying circuit 26 is unnecessary.

[Ninth Embodiment] FIG. 20 shows, as a ninth embodiment of the present invention, a four-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 4 (hereinafter referred to as an optical intensity modulator). 4) will be described.

The optical transmission circuit shown in FIG. 20 comprises a light intensity modulator 4 shown in FIG. 4, a CW light source 13, and four electric filters (LPF, two BPFs and HPFs) 1 on a substrate 23.
9 ₁ , 19 ₂ , 19 ₃ , 19 ₄ and four drive circuits 21
₁ , 21 ₂ , 21 ₃ , 21 ₄ and three phase adjusting circuits 2
5 ₁ , 25 ₂ , 25 ₃ , a differential amplifier circuit 30, and two 2-branch circuits 32 ₁ , 32 ₂ . In addition to these, on the base material 23, a bias applying circuit 26,
An optical amplifier circuit 27, an electric input terminal 28 ₁ and an optical output terminal 29 are provided. Although not shown in FIG. 20, the optical intensity modulator 4 has two arms 7 ₁ as shown in FIG.
_Two electrodes are formed symmetrically on each of 7 _{2 such} as an electrode 8 ₁ and an electrode 8 ₃ and an electrode 8 ₂ and an electrode 8 ₄ . The gain adjustment circuit is omitted.

In FIG. 20, the electric input terminal 28₁Difference
The input end of the dynamic amplification circuit 30 is connected to the differential amplification circuit 30.
One of the two output terminals of
Road 32₁Input end is electrically connected, the other one output
The other one two-branch circuit 32 at the end₂The input end of is electrically connected
Has been continued. One 2-branch circuit 32₁Two output terminals
Drive circuit 21 at one of the output terminals₁, LPF19₁
And electrode 8₁Are electrically connected in this order, and the other
Drive circuit 21 at the output end of₃, BPF19₃, Phase adjustment times
Road 25₃And electrode 8₃Are electrically connected in this order
There is. In addition, the other one of the two branch circuits 32₂Two outputs of
The drive circuit 21 is provided at one of the output ends. ₂, BPF19
₂And electrode 8₁₂Are electrically connected in this order and the other
Drive circuit 21 at one output end_Four, HPF19_Four, Phase adjustment
Circuit 25₃And electrode 8_FourAre electrically connected in this order
ing. In addition, CW light source 13, light intensity modulator 1,
The width circuit 27 and the optical output terminal 29 are optically connected in this order.
Has been continued. The bias applying circuit 26 includes the light intensity modulator 3
Is connected to a bias electrode (not shown).

Continuous light from the CW light source 13 is input to the light intensity modulator 4, and the optical data signal 17 of the light intensity modulator 4 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27.

Electric input terminal 28₁Has a single-ended
The electrical data signal 15 is input. Electric input terminal 28₁
From the electric data signal 15 inputted from the differential amplifier circuit 3
By setting 0, two differential signals corresponding to the electrical data signal 15
Qi signal 31₁, 31₂Is output. One differential telegraph
No. 31₁Is a two-branch circuit 32₁Two electrical data by
Signal 33₁, 33₃Branched to. Differential electricity on one side
Signal 31₁Is a two-branch circuit 32₂Two electric days by
Signal 33₂, 33_FourBranched to. 4 forked
Signal 33₁, 33₂, 33₃, 33_FourThe first of the
Qi data signal 33₁Is the drive circuit 21₁Amplified in
After that, LPF19₁The first mid-frequency component and the second
Mid frequency components and high frequency components are cut off. First,
The second mid-frequency component and high-frequency component are cut off
Qi data signal 20₁Is the electrode 8 of the light intensity modulator 4₁Applied to
To be done. Drive circuit 21₁And LPF19₁The order of
This is a question, and the opposite is okay. Second electrical data signal
33₂Is the drive circuit 21₂BPF19 after being amplified by
₂Low frequency component, second mid frequency component and high frequency
The frequency component is cut off, and the phase adjustment circuit 25₁By phase
Adjusted. Low frequency component and second mid frequency component
Electricity with high frequency components cut off and phase adjusted
Data signal 20₂Is the electrode 8 of the light intensity modulator 4₂Applied to
Be done. Drive circuit 21₂, BPF19₂And phase adjustment times
Road 25₁The order of does not matter before and after, and can be changed.
Does not support. Third electrical data signal 33₃Is the drive circuit 2
1₃BPF19 after being amplified by₃Due to low frequency
Minute, the first mid frequency component and the high frequency component are cut off.
Phase adjustment circuit 25₂The phase is adjusted by. Low frequency
The wave number component, the first middle frequency component and the high frequency component are blocked.
Electrical data signal 20 disconnected and phase adjusted₃But
Electrode 8 of light intensity modulator 4₃Applied to. Drive circuit 21
₃, BPF19₃And phase adjustment circuit 25₂The order is before
It doesn't matter what you do, and you can change it. further,
Fourth electrical data signal 33_FourIs the drive circuit 21 _FourAmplified by
After being done, HPF19_FourDue to the low frequency component and the first
The mid frequency component and the second mid frequency component are cut off,
Phase adjustment circuit 25₃The phase is adjusted by. Low frequency composition
Minute, the first and second mid frequency components are cut off, and
Phase adjusted electrical data signal 20_FourOf the light intensity modulator 4
Electrode 8_FourApplied to. Drive circuit 21_Four, HPF19_Four
And phase adjustment circuit 25₃The order of
It doesn't matter if they are replaced.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And BPF19₂When
Total pass band characteristics of the drive circuit 21₃And BPF
19 ₃And the total pass band characteristics of the drive circuit 21_Four
And HPF19_FourAnd the relationship with the total passband characteristics
Is the electric frequency band when the four frequencies are overlapped.
The signal frequency band included in the data signal 15 is substantially included.
As described above, the pass band characteristic 40 shown in FIG.₁, 40₂Four
0₃, 40_FourIs set to. At that time,
The gain adjustment circuit ensures that the frequency characteristics of the entire optical transmission circuit are flat.
Adjusted to be a supporter. In addition, four electric fills
If the pass frequency bands of the
The signal frequency band of the electrical data signal 15 is substantially several bands
As long as the condition that includes₁Or
HPF19_FourAt least one of them may be BPF
Yes.

The phase adjusting circuits 25 ₁ , 25 ₂ , and 25 ₃ are 4
It is used to adjust the phase between the electrical data signals applied to the one electrode 8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ , and is generated by the differential amplifier circuit 30 and the two two-branch circuits 32 ₁ , 32 ₂ . Four electrical data signals 33 ₁ , 33 ₂ , 3
3 _3, 33 ₄ of the route, the electrical length from the electrical input terminal 28 ₁ and the electrical length from the electrode ₈₁ of the light intensity modulator 4, the electrical input terminals 28 ₁ to the electrode ₈₂ of the light intensity modulator 4 When,
And the electrical length from the electrical input terminals 28 ₁ to the electrode 8 ₃ of the light intensity modulator 4, the electrical length and the phase adjustment so that the same length from the electrical input terminals 28 ₁ to the electrode 8 ₄ of the light intensity modulator 4 Adjusted by the circuits 25 ₁ , 25 ₂ , 25 ₃ . If the length is equal from the beginning, the phase adjusting circuit is not necessary.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 3, and the bias applying circuit 26 is designed to maximize the amplitude of the optical data signal 17 output from the light intensity modulator 3. Applies a bias voltage. Even if the bias applying circuit 26 is not used, if the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning,
The bias applying circuit 26 is unnecessary.

[Tenth Embodiment] FIG. 22 shows, as a tenth embodiment, the two-electrode optical phase modulator 5 shown in FIG.
An optical transmission circuit using an optical phase modulator 5 will be shown. This optical phase modulator 5 has one arm (optical waveguide) 7 ₁ .
It has two electrodes 8 ₁ and 8 ₂ on it. 9
Is an input optical port, and 11 is an output optical port.

The optical transmission circuit of FIG. 22 has the optical phase modulator (two-electrode optical phase modulator) 5 shown in FIG.
, CW light source 13, two electric filters (LPF and HPF) 19 ₁ , 19 ₂ and two drive circuits 21 ₁ ,
21 ₂ , a phase adjusting circuit 25 ₁ and a two-branching circuit 32 ₁ . Gain adjustment circuit and bias application circuit,
Illustration of the optical amplifier circuit, the electric input terminal, and the optical output terminal is omitted.

Continuous light from the CW light source 13 is input to the optical phase modulator 5, and the optical data signal 17 of the optical phase modulator 5 is inputted.
Is transmitted from the optical output terminal via the optical amplifier as appropriate.

From the single-ended electric data signal 15 input from the electric input terminal, two electric data signals 3 corresponding to the electric data signal 15 by the two-branching circuit 32 ₁ .
2 ₁ and 32 ₂ are branched. Of the signals branched by the two-branching circuit 32 ₁ , one electric data signal 33 ₁ is amplified by the driving circuit 21 ₁ , and then the high frequency component is blocked by the LPF 19 ₁ . The electrical data signal 20 ₁ from which the high frequency components are blocked is applied to the electrode 8 ₁ of the optical phase modulator 5. The order of the drive circuit 21 ₁ and the LPF 19 ₁ does not matter before or after, and may be reversed. The other electric data signal 33 ₂ is phase-adjusted by the phase adjustment circuit 25 ₁ , is then amplified by the drive circuit 21 ₂ , and the low frequency component is blocked by the HPF 19 ₂ . The electrical data signal 20 ₂ with the low frequency components blocked and the phase adjusted is applied to the electrode 8 ₂ of the optical phase modulator 5. Drive circuit 21 ₂ ,
The order of the HPF 19 ₂ and the phase adjusting circuit 25 ₁ does not matter before and after, and they may be interchanged. Further, if the pass frequency bands of the two electric filters are overlapped, the LPF is satisfied as long as the condition that the entire pass frequency band substantially includes the signal frequency band of the electric data signal 15 is satisfied.
19 ₁ or at least one of HPF 19 ₂ is BP
It may be F.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And HPF19₂When
The relationship with the total passband characteristics of
The passing frequency band when the electric data signal 15 has
Shown in FIG. 10 to substantially include the signal frequency band
Passband characteristics 22₁, 22₂Is set to. That
In this case, if necessary, use the gain adjustment circuit to
Is adjusted so that the frequency characteristic of is flat.

The phase adjustment circuit 25 ₁ has two electrodes 8 ₁ and 8 ₁ .
It is used to adjust the phase between the electrical data signals applied to the _two , and of the two electrical data signals 33 ₁ and 33 ₂ branched by the two-branching circuit 32 ₁ , the optical phase from the electrical input terminal The phase adjustment circuit 25 ₁ adjusts the electrical length to the electrode 8 ₁ of the modulator 5 and the electrical length from the electrical input terminal to the electrode 8 ₂ of the optical phase modulator 5 to be equal. If the length is equal from the beginning, the phase adjusting circuit is not necessary.

LPF 19 ₁ and HPF in the tenth embodiment
19 ₂ and 2-branch circuit 32 ₁ are connected to the seventh embodiment (FIG. 1).
Similar to 6), it can be replaced with one frequency division circuit 34.

Further, in the optical transmission circuit of the tenth embodiment,
Although the optical phase modulator 5 having the _two electrodes 8 ₁ and 8 ₂ is used, the number of drive circuits and electric filters is increased even if the optical phase modulator 5 is expanded to have three or more electrodes. The optical transmission circuit can be similarly configured by increasing the number of electrodes according to the number of electrodes.

By thus using one optical phase modulator having a plurality of electrodes and a plurality of electric filters,
The band of each drive circuit has an advantage that the band can be narrower than that of the drive circuit in the general optical transmission circuit of FIG. Further, an optical transmission circuit that obtains an optical output signal corresponding to an input electric signal by adding a frequency-divided electric signal to one optical phase modulator having a plurality of electrodes uses two conventional optical modulators. Compared with the case, the electric signal path after frequency division can be shortened, which is stable, and the insertion loss of the modulator is 1
It has the advantage of being small. Further, there is an advantage that the cost of the optical modulator having a plurality of electrodes is smaller than that of two optical modulators having one electrode.

[Eleventh Embodiment] FIG. 23 shows the first embodiment of the present invention.
As one embodiment, a configuration in which the differential amplifier circuit is omitted from the optical transmission circuit (using the four-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator 4) shown in FIG. 20 is shown.

The optical transmission circuit shown in FIG. 23 comprises a light intensity modulator 4 shown in FIG. 4, a CW light source 13, four electric filters (LPF, two BPFs and HPF) 1 on a substrate 23.
9 ₁ , 19 ₂ , 19 ₃ , 19 ₄ and four drive circuits 21
₁ , 21 ₂ , 21 ₃ , 21 ₄ and three phase adjusting circuits 2
5 ₁ , 25 ₂ , 25 ₃ and two 2-branch circuits 32 ₁ , 3
It is equipped with 2 ₂ . In addition to these, on the base material 23, a bias applying circuit 26, an optical amplifier circuit 27,
It is provided with individual electric input terminals 28 ₁ and 28 ₂ and a light output terminal 29. The gain adjustment circuit is omitted.

In FIG. 23, one electric input terminal 28
₁From one of the two branch circuits 32₁To single-ended electricity
The data signal 15 is input, and the other one electric input terminal 2
8₂To the other one of the two branch circuits 32₂To electrical data signal
The logic inversion signal 16 of 15 is input. One bifurcation
Road 32₁One of the two output terminals of
Road 21₁, LPF19₁And electrode 8₁Electricity in this order
Drive circuit 21 is connected to the other output terminal.₃, B
PF19₃, Phase adjustment circuit 25₃And electrode 8 ₃But this
They are electrically connected in sequence. Also, the other two branches
Circuit 32₂Drives one of the two output terminals
Circuit 21₂, BPF19₂And electrode 8 ₁₂In this order
The driver circuit 21 is electrically connected to the other output end._Four,
HPF19_Four, Phase adjustment circuit 25₃And electrode 8_FourGako
Are electrically connected in this order. Furthermore, CW light source 1
3, light intensity modulator 1, light amplification circuit 27 and light output terminal
29 are optically connected in this order. Bias application
The circuit 26 is a bias electrode (not shown) of the light intensity modulator 3.
It is connected to the.

Continuous light from the CW light source 13 is input to the light intensity modulator 4, and the optical data signal 17 of the light intensity modulator 4 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27.

The electrical data signal 15 is one of the two branch circuits 3
Two₁With two electrical data signals 33₁, 32₃Branched into
The logic inversion signal 16 is output to the other branch circuit 32.₂In 2
One electrical data signal 33₂, 33_FourBranched to. Branch
Four signals 33₁, 33 ₂, 33₃, 33_FourNou
Then, the first electrical data signal 33₁Is the drive circuit 21₁so
LPF19 after being amplified₁The first mid-range frequency
The second, middle and high frequency components are cut off
It The first and second mid frequency components and high frequency components are
Electrical data signal 20 disconnected₁Is the electrode of the light intensity modulator 4
8₁Applied to. Drive circuit 21₁And LPF19₁Order of
The order does not matter before and after, and the reverse is okay. Second electricity
Data signal 33₂Is the drive circuit 21₂After being amplified by
BPF19 ₂The low frequency component and the second mid frequency
Phase adjustment circuit 25₁
The phase is adjusted by. Low frequency component and second mid-range
Wave number component and high frequency component are cut off, and phase adjustment
Electrical data signal 20₂Is the electrode 8 of the light intensity modulator 4
₂Applied to. Drive circuit 21₂, BPF19₂and
Phase adjustment circuit 25₁The order of
It doesn't matter. Third electrical data signal 33₃Is
Drive circuit 21₃BPF19 after being amplified by₃Due to
Band frequency component and first middle band frequency component and high band frequency component
Is cut off and the phase adjustment circuit 25₂Phase is adjusted by
It Low frequency component, first middle frequency component and high frequency
Electrical data signal with several components blocked and phase adjusted
No. 20₃Is the electrode 8 of the light intensity modulator 4₃Applied to. Drive
Circuit 21₃, BPF19₃And phase adjustment circuit 25₂
It does not matter if the order is
Yes. In addition, the fourth electrical data signal 33_FourIs the drive circuit
21_FourHPF19 after being amplified in_FourDue to low frequency
Component and the first mid-range frequency component and the second mid-range frequency component
Phase cutoff circuit 25₃The phase is adjusted by.
The low frequency components and the first and second mid frequency components are blocked.
And phase adjusted electrical data signal 20_FourIs light
Electrode 8 of the degree modulator 4_FourApplied to. Drive circuit 21_Four,
HPF19_FourAnd phase adjustment circuit 25₃The order of
This is a question and may be replaced.

[Twelfth Embodiment] FIG. 24 shows the first embodiment of the present invention.
As a second embodiment, in the optical transmission circuit of the eleventh embodiment (FIG. 20), one electrode 8 ₄ of the four-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator ₄ is not used, and it corresponds to this. The configuration in which one branch circuit, one drive circuit, one electric filter, and one phase adjustment circuit are omitted is shown.

The optical transmission circuit shown in FIG.
The light intensity modulator 4 shown in FIG. 4, the CW light source 13, and the three
Electrical filter (LPF, BPF and HPF) 19₁,
19 ₂, 19₃And three drive circuits 21₁, 21₂Two
1₃And one 2-branch circuit 32₁And two phase adjustment times
Road 25₁, 25₂With a differential amplifier circuit 30
is there. In addition to these, a bias is applied on the base material 23.
Circuit 26, optical amplifier circuit 27, and electric input terminal 28
₁And a light output terminal 29. Note that the gain adjustment times
The road is omitted.

In FIG. 24, the electric input terminal 28₁From
Single-ended electrical data signal 15 to the differential amplifier 30
Is input, and the two-branch circuit 32 is provided at one output end.₁Is connected
Drive circuit 21 at the other output end.₂Is connected
It 2-branch circuit 32₁One of the two output terminals of
Drive circuit 21 at the power end₁, LPF19₁And electrode 8₁But
Electrically connected in this order and drive to the other output end.
Road 21₃, BPF19 ₃, Phase adjustment circuit 25₂And electricity
Pole 8₃Are electrically connected in this order. Drive circuit 2
1₂To BPF19₂, Phase adjustment circuit 25₁And electrodes
8₂Are electrically connected in this order. Furthermore, CW
Light source 13, light intensity modulator 1, light amplification circuit 27 and light output
The force terminal 29 is optically connected in this order. Bahia
The voltage application circuit 26 is a bias electrode of the light intensity modulator 3 (shown in the figure.
Connected). The electrode 8_FourIs used
Not in. The gain adjustment circuit is omitted.

Continuous light from the CW light source 13 is input to the light intensity modulator 4, and the optical data signal 17 of the light intensity modulator 4 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27. The optical amplifier 27 is used to increase the transmission output of the optical transmission circuit, and is unnecessary when the optical output may be small.

The electrical data signal 1 is output by the differential amplifier circuit 30.
Two differential electrical signals 31 corresponding to 5₁, 31₂Made by
One differential signal is 31₁Is a two-branch circuit 32₁Two
Electrical data signal 33₁, 32₃Branched to. Three
Signal 33₁, 31₂, 33₃Of the first electrical data
Signal 33₁Is the drive circuit 21₁LPF after amplified by
19₁Cuts off mid-range and high-frequency components.
Be done. Electricity with mid-frequency components and high-frequency components cut off
Qi data signal 20₁Is the electrode 8 of the light intensity modulator 4 ₁Applied to
To be done. Drive circuit 21₁And LPF19₁The order of
This is a question, and the opposite is okay. Second electrical data signal
31₂Is the drive circuit 21₂BPF19 after being amplified by
₂Cuts off low-frequency components and high-frequency components,
Phase adjustment circuit 25₁The phase is adjusted by. Low frequency
Components, mid frequency components and high frequency components are cut off,
The phase-adjusted electrical data signal 20₂Is light intensity modulation
Electrode 8 of container 4₂Applied to. Drive circuit 21₂, BPF
19₂And phase adjustment circuit 25₁The order of
It can be replaced. Third electrical data signal
No. 33₃Is the drive circuit 21₃HPF1 after being amplified by
9₃Block low frequency components and mid frequency components.
Phase adjustment circuit 25₂The phase is adjusted by. Low frequency
Wave number component and mid frequency component are cut off, and phase adjustment
Electrical data signal 20₃Is the electrode 8 of the light intensity modulator 4
₃Applied to. Drive circuit 21₃, BPF19₃and
Phase adjustment circuit 25₂The order of
It doesn't matter.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And BPF19₂When
Total pass band characteristics of the drive circuit 21₃And HPF
19 ₃The relationship with the total passband characteristics is
Electrical data signal 1 is the pass frequency band when superposed
1 to substantially include the signal frequency band of FIG.
Passband characteristics 39 shown in 9₁, 39₂, 39₃Set to
Has been done. At that time, a gain adjustment circuit (not shown)
Adjust so that the frequency characteristics of the entire optical transmitter circuit become flat.
Be adjusted.

Phase adjusting circuit 25₁, 25₂Has 3 electrodes
8₁, 8₂, 8₃The phase between the electrical data signals applied to
It is used to adjust the differential amplifier circuit 30 and
And two two-branch circuit 32₁4 electrical days generated by
Signal 33₁, 31₂, 33 ₃Electrical input out of the path
Terminal 28₁From the electrode 8 of the light intensity modulator 4₁Electrical length up to
And the electric input terminal 28₁From the electrode 8 of the light intensity modulator 4₂
Electrical length up to and electrical input terminal 28₁From the light intensity modulator
4 electrodes 8₃Phase adjustment so that the electrical length up to
Adjustment circuit 25₁, 25₂Adjusted by. Phase adjustment circuit
25₁, 25₂Even if you don't use
If there is, phase adjustment circuit 25₁, 25₂Is unnecessary.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 4, and the bias applying circuit 26 is set so that the amplitude of the optical data signal 17 output from the light intensity modulator 4 becomes maximum. Applies a bias voltage. Even if the bias applying circuit 26 is not used, if the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning,
The bias applying circuit 26 is unnecessary.

As in the twelfth embodiment, even if the electrodes are used in an unbalanced manner between the _two arms 7 ₁ and 7 ₂ of the push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 4, the optical intensity modulation is performed. It can be performed. In this case, it is also possible to use a Mach-Zehnder interferometer type optical intensity modulator in which the number of electrodes between the _two arms 7 ₁ and 7 ₂ is unbalanced from the beginning, and these are equivalent.

[Thirteenth Embodiment] FIG. 25 shows the first embodiment of the present invention.
As a third embodiment, a configuration in which the differential amplifier circuit is omitted from the optical transmission circuit of the twelfth embodiment (FIG. 24) is shown.

The optical transmission circuit shown in FIG.
The light intensity modulator 4 shown in FIG. 4, the CW light source 13, and the three
Electrical filter (LPF, BPF and HPF) 19₁,
19 ₂, 19₃And three drive circuits 21₁, 21₂Two
1₃And one 2-branch circuit 32₁And two phase adjustment times
Road 25₁, 25₂It is equipped with. In addition to these
On the base material 23, a bias applying circuit 26 and an optical amplifier are provided.
Circuit 27 and two electrical input terminals 28₁, 28₂And the light
The output terminal 29 is provided. The gain adjustment circuit is shown
Is omitted.

In FIG. 25, one electric input terminal 28
₁To 2 branch circuits 32₁Single-ended electrical data on
The signal 15 is input, and the other electrical input terminal 28₂Or
Drive circuit 32₂To the logical inversion signal of the electrical data signal 15
16 is input. 2-branch circuit 32₁Of the two output ends of
The drive circuit 21 is provided at one of the output terminals.₁, LPF19₁Oh
And electrode 8₁Are electrically connected in this order, and the other
Drive circuit 21 at the output end ₃, HPF19₃, Phase adjustment circuit
25₂And electrode 8₃Are electrically connected in this order
It In addition, the drive circuit 21₂BPF1 is at the output end of
9₂, Phase adjustment circuit 25₁And electrode 8₂In this order
Be connected physically. Furthermore, CW light source 13, light intensity
The modulator 1, the optical amplifier circuit 27 and the optical output terminal 29 are
Optically connected in sequence. The bias applying circuit 26
It is connected to the bias electrode (not shown) of the light intensity modulator 3.
ing.

Continuous light from the CW light source 13 is input to the light intensity modulator 4, and the optical data signal 17 of the light intensity modulator 4 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27.

The electrical data signal 15 is sent to the 2-branch circuit 32.₁so
Two electrical data signals 33₁, 32 ₃Branched to. Three
One signal 33₁, 16, 33₃Out of the first electrical day
Signal 33₁Is the drive circuit 21₁After being amplified by LP
F19₁Cuts off mid-frequency and high-frequency components
To be done. Mid frequency components and high frequency components are cut off
Electrical data signal 20₁Is the electrode 8 of the light intensity modulator 4₁Mark on
Be added. Drive circuit 21₁And LPF19₁Order is before and after
It doesn't matter, and the opposite is okay. Second electrical data signal
No. 16 is a drive circuit 21₂BPF19 after being amplified by
₂Cuts off low-frequency components and high-frequency components,
Phase adjustment circuit 25₁The phase is adjusted by. Low frequency
Components and high frequency components are cut off and the phase is adjusted.
Electrical data signal 20₂Is the electrode 8 of the light intensity modulator 4₂To
Is applied. Drive circuit 21₂, BPF19₂And phase
Adjustment circuit 25₁The order does not matter before and after,
It doesn't matter. Third electrical data signal 33₃Drive
Circuit 21₃BPF19 after being amplified by₃Due to low frequency
The wave number component and the middle frequency component are cut off, and the phase adjustment circuit 2
5₂The phase is adjusted by. Low frequency components and mid frequencies
Electrical data signal with several components blocked and phase adjusted
No. 20₃Is the electrode 8 of the light intensity modulator 4₃Applied to. Drive
Circuit 21₃, BPF19₃And phase adjustment circuit 25₂
It does not matter if the order is
Yes.

[Fourteenth Embodiment] FIG. 26 shows the first embodiment of the present invention.
As a fourth embodiment, a configuration of an optical transmission circuit using the 6-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator 6 (hereinafter referred to as the optical intensity modulator 6) shown in FIG. 6 is shown.

The optical transmission circuit shown in FIG. 26 comprises a light intensity modulator 6 shown in FIG. 6, a CW light source 13, six electric filters (LPF, two BPFs and HPF) 1 on a substrate 23.
9 ₁ , 19 ₂ , 19 ₃ , 19 ₄ and 6 drive circuits 21
₁ , 21 ₂ , 21 ₃ , 21 ₄ and 5 phase adjustment circuits 2
5 ₁ , 25 ₂ , 25 ₃ , a differential amplifier circuit 30, and two 3-branch circuits 37 ₁ , 37 ₂ . In addition to these, on the base material 23, a bias applying circuit 26,
An optical amplifier circuit 27, an electric input terminal 28 ₁ and an optical output terminal 29 are provided. Although not shown in FIG. 26, the light intensity modulator 6 has two arms 7 ₁ as shown in FIG.
Electrodes 8 ₁ , 8 ₃ and 8 ₅ and electrodes 8 ₂ , 8 ₄ and 8 ₆ are formed in each of 7 _{2 in} a symmetrical arrangement of three electrodes. The gain adjustment circuit is not shown.

In FIG. 26, the input end of the differential amplifier circuit 30 is connected to the electric input terminal 28 _1, and the differential amplifier circuit 30 is connected.
One of the two output terminals of the three output terminals is electrically connected to _one input terminal of the three-branch circuit 37 ₁ , and the other one output terminal is connected to the other input terminal of the three-branch circuit 37 _2. It is electrically connected. Of one 3 the two output ends of the branch circuit 37 _1, the drive circuit 21 ₁ to the first output terminal, LPF 19 ₁
And the electrode 8 ₁ are electrically connected in this order, and the drive circuit 21 ₃ , BPF 19 ₃ , and phase adjustment circuit 2 are connected to the second output end.
5 ₃ and the electrode 8 ₃ are electrically connected in this order,
The drive circuit 21 ₅ , the BPF 19 ₅ , the phase adjustment circuit 25 ₄ and the electrode 8 ₅ are electrically connected in this order to the output terminal of the. Further, among the three output terminals of the other one of the three branch circuits 37 ₂ , the drive circuit 21 ₂ and the BPF 19 are connected to the first output terminal.
₂ , the phase adjustment circuit 25 ₁ and the electrode 8 ₂ are electrically connected in this order, and the drive circuit 21 ₄ , BPF and BPF are connected to the second output end.
19 ₄ , the phase adjusting circuit 25 ₃ and the electrode 8 ₄ are electrically connected in this order, and the driving circuit 21 ₆ , H is connected to the third output end.
The PF 19 ₆ , the phase adjustment circuit 25 ₅ and the electrode 8 ₆ are electrically connected in this order. Furthermore, the CW light source 13,
Optical intensity modulator 1, optical amplifier circuit 27 and optical output terminal 29
Are optically connected in this order. The bias applying circuit 26 is connected to the bias electrode (not shown) of the light intensity modulator 3.

Continuous light from the CW light source 13 is input to the light intensity modulator 4, and the optical data signal 17 of the light intensity modulator 4 is inputted.
Is transmitted from the optical output terminal 29 via the optical amplifier 27.

Electric input terminal 28₁Has a single-ended
The electrical data signal 15 is input. Electric input terminal 28₁
From the electric data signal 15 inputted from the differential amplifier circuit 3
By setting 0, two differential signals corresponding to the electrical data signal 15
Qi signal 31₁, 31₂Is output. One differential telegraph
No. 31₁Is a three-branch circuit 37₁3 electrical data by
Signal 38₁, 38₃, 38_FiveBranched to. The other one
Differential electrical signal 31₁Is a three-branch circuit 37₂By three
Electrical data signal 38₂, 38_Four, 38₆Branched to.
Six branched signals 38₁, 38₂, 38₃Three
8_Four, 38_Five, 38 ₆Of the first electrical data signal 3
8₁Is the drive circuit 21₁LPF19 after being amplified by₁
And the first middle frequency component and the second middle frequency component
Third mid frequency component, fourth mid frequency component and high frequency
The wave number component is cut off. First, second, third and fourth midrange
Electrical data signal with frequency components and high frequency components cut off
No. 20 ₁Is the electrode 8 of the light intensity modulator 4₁Applied to. Drive
Circuit 21₁And LPF19₁The order of does not matter,
The opposite is okay. Second electrical data signal 38₂Is
Drive circuit 21₂BPF19 after being amplified by₂Due to
High frequency components and second, third and fourth mid frequency components
The frequency component is cut off, and the phase adjustment circuit 25₁By
Phase adjusted. Low frequency components and second, third, fourth
The high frequency component and high frequency component are cut off, and the phase
Conditioned electrical data signal 20₂Is the power of the light intensity modulator 4
Pole 8₂Applied to. Drive circuit 21₂, BPF19₂Oh
And phase adjustment circuit 25₁The order of
You can change it. Third electrical data signal 38₃
Is the drive circuit 21₃BPF19 after being amplified by₃By
Low frequency components and first, third and fourth mid frequency components
And high frequency components are cut off, and the phase adjustment circuit 25₂By
The phase is adjusted. Low frequency components and first, third and fourth
The mid-range and high-range frequency components are cut off, and
Phase adjusted electrical data signal 20₃Is the light intensity modulator 4
Electrode 8₃Applied to. Drive circuit 21₃, BPF19
₃And phase adjustment circuit 25₂The order of does not matter,
It can be replaced. Fourth electrical data signal 3
8_FourIs the drive circuit 21_FourBPF19 after being amplified by_Four
The low frequency components and the first, second and fourth mid frequencies
The component and the high frequency component are cut off, and the phase adjustment circuit 25
₃The phase is adjusted by. Low frequency components and first and second
2, the 4th middle frequency component and high frequency component are cut off
And phase adjusted electrical data signal 20_FourIs light
Electrode 8 of the degree modulator 4_FourApplied to. Drive circuit 21_Four,
HPF19_FourAnd phase adjustment circuit 25₃The order of
This is a question, and it does not matter if they are replaced. Fifth electric device
Data signal 38_FiveIs the drive circuit 21_FiveAfter being amplified by B
PF19_FiveLower frequency component and the first mid frequency component
Minute, second mid-range frequency component, third mid-range frequency component and high
The frequency component is cut off, and the phase adjustment circuit 25_FourBy
Phase adjusted. Low frequency component and first, second, third
The high frequency component and high frequency component are cut off, and the phase
Conditioned electrical data signal 20_FiveIs the power of the light intensity modulator 4
Pole 8_FiveApplied to. Drive circuit 21 _Five, HPF19_FiveOh
And phase adjustment circuit 25_FourThe order of
You can change it. In addition, the sixth electrical data signal
No. 38₆Is the drive circuit 21₆HPF1 after being amplified by
9₆The low frequency component and the first mid frequency component
2 middle frequency components, 3rd middle frequency components, and 4th middle frequency components
The frequency component is cut off, and the phase adjustment circuit 25_FiveBy
Phase adjusted. Low frequency components and the first, second, third and second
4 mid-range frequency components were cut off and phase adjusted
Electrical data signal 20₆Is the electrode 8 of the light intensity modulator 4₆Mark on
Be added. Drive circuit 21₆, HPF19 ₆And phase
Adjustment circuit 25_FiveThe order of does not matter, even if it is replaced
It doesn't matter. In addition, the pass frequencies of the six electrical filters
By overlapping several bands, the overall pass frequency band is
It is said that the signal frequency band of the electrical data signal 15 is included
As long as the conditions are satisfied, LPF19₁Or HPF19₆
At least one of them may be the BPF.

Drive circuit 21₁And LPF19₁Tota with
Pass band characteristics and drive circuit 21 ₂And BPF19₂When
Total pass band characteristics of the drive circuit 21₃And BPF
19 ₃And the total pass band characteristics of the drive circuit 21_Four
And BPF19_FourAnd the total pass band characteristics of the
Road 21_FiveAnd BPF19_FiveAnd total passband characteristics
And the drive circuit 21₆And HPF19₆Total passage with
The relationship with the band characteristic is that the passing frequency when 6 persons are overlapped
A signal frequency band having a wave number band of the electrical data signal 15
To substantially include the pass band characteristic 4 shown in FIG.
0₁, 40₂, 40₃, 40_FourIs set according to
It At that time, optical transmission is performed by a gain adjustment circuit (not shown).
The frequency characteristic of the entire circuit is adjusted to be flat.

Phase adjusting circuit 25₁, 25₂, 25₃Two
5_Four, 25_FiveHas 6 electrodes 8₁, 8 ₂, 8₃, 8_Four, 8
_Five, 8₆The phase between the electrical data signals applied to the
6 electrical data signals 33 used for₁,
33₂, 33₃, 33_Four, 33_Five, 33₆The path of electricity
Phase adjustment circuit 25 so that the lengths are equal₁, 25₂Two
5₃, 25_Four, 25_FiveAdjusted by. Isometric from the beginning
If so, the phase adjustment circuit is unnecessary.

The bias applying circuit 26 sets an appropriate bias voltage to the light intensity modulator 3, and the bias applying circuit 26 is designed to maximize the amplitude of the optical data signal 17 output from the light intensity modulator 3. Applies a bias voltage. If the amplitude of the optical data signal 17 is maximum or sufficiently large from the beginning, the bias applying circuit 26 is unnecessary.

Also in the fourteenth embodiment, as in the eleventh embodiment (FIG. 23), the differential amplifier circuit 30 is omitted, and the single-ended electric data signal 15 and its logic inverted signal 16 are converted into two electric data. One of the three branch circuits 37 ₁ and the other one of the three branch circuits 37 ₂ from the input terminals 28 ₁ and 28 ₂ respectively.
Can be configured to enter and branch.

Further, similarly to the twelfth embodiment (FIG. 24),
The light intensity modulation can be performed between the _two arms 7 ₁ and 7 _{2 of the} push-pull electrode type Mach-Zehnder interferometric light intensity modulator 6 even if the electrodes are unbalanced. In this case, for three electrodes in one arm, 1
When only one is used, one branch circuit can be omitted, two drive circuits, two electric filters, and two phase adjustment circuits can be omitted, and the differential amplifier circuit can also be omitted. Of the three electrodes in one arm, 2
When only one is used, the 3-branch circuit is made into a 2-branch circuit,
One drive circuit, one electrical filter and one phase adjustment circuit can be omitted. In any case, a Mach-Zehnder interferometer type optical intensity modulator in which the number of electrodes is unbalanced from the beginning between the _two arms 7 ₁ and 7 ₂ can be used, and these are equivalent.

[0142]

As can be seen from the above description, according to the present invention, a conventional optical transmission circuit that obtains an optical output signal corresponding to an input electric signal by performing electro-optical conversion by a plurality of individual optical modulators. Compared with, it has the following effects. (1) Since the input electric signal is frequency-divided, the performance requirements for the drive circuit of the conventional optical transmission circuit can be relaxed, which greatly contributes to cost reduction of the optical transmission circuit. (2) In addition to this, since the optical transmitter circuit is realized by one optical modulator having a plurality of electrodes, it is possible to realize an optical transmitter circuit that is stable, has low insertion loss, and has a low optical modulator cost. . (3) Therefore, the optical transmission circuit of the present invention can realize the cost reduction of the optical modulator and the drive circuit, which are extremely expensive parts, without impairing the performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a two-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator.

FIG. 2 is a diagram showing a two-electrode Mach-Zehnder interferometric light intensity modulator.

FIG. 3 is a diagram showing a three-electrode Mach-Zehnder interferometric light intensity modulator.

FIG. 4 is a diagram showing a four-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator.

FIG. 5 is a diagram showing a two-electrode optical phase modulator.

FIG. 6 is a view showing a 6-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator.

FIG. 7 is a diagram showing a configuration of a general optical transmission circuit using a two-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator.

8 is a voltage Vm1 of an electrical data signal actually applied to one electrode and a voltage Vm2 of a logic inversion signal actually applied to another electrode in the optical transmission circuit of FIG.
FIG. 5 is a diagram showing the relationship between the output power Po and the optical data signal Po.

FIG. 9 is a diagram showing a configuration of an optical transmission circuit using a two-electrode push-pull electrode type Mach-Zehnder interferometric light intensity modulator as a first embodiment of the present invention.

10 is a diagram showing a relationship between two pass band characteristics in the optical transmission circuit of FIG.

FIG. 11 is a diagram showing a configuration of an optical transmission circuit similar to that of FIG. 9 as a second embodiment of the present invention.

FIG. 12 is a diagram showing the configuration of another optical transmission circuit using a two-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator as a third embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of an optical transmission circuit similar to that of FIG. 12 as a fourth embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of an optical transmission circuit using a two-electrode Mach-Zehnder interferometer type optical intensity modulator as a fifth embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of an optical transmission circuit similar to that of FIG. 14 as a sixth embodiment of the present invention.

16 is a diagram showing a configuration in which an electric filter and a branch circuit in the optical transmission circuit of FIG. 15 are realized by a single frequency division circuit as a seventh embodiment of the present invention.

FIG. 17 is a diagram showing a configuration example of a frequency division circuit and a transmission characteristic.

FIG. 18 is a diagram showing a configuration of an optical transmission circuit using a three-electrode Mach-Zehnder interferometric light intensity modulator as an eighth embodiment of the present invention.

19 is a diagram showing a relationship between three pass band characteristics in the optical transmission circuit of FIG.

FIG. 20 is a diagram showing the configuration of an optical transmission circuit using a four-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator as a ninth embodiment of the present invention.

21 is a diagram showing the relationship between four pass band characteristics in the optical transmission circuit of FIG.

FIG. 22 is a diagram showing the configuration of an optical transmission circuit using a two-electrode optical phase modulator as a tenth embodiment of the present invention.

FIG. 23 is a diagram showing a configuration in which a differential amplifier is omitted from the optical transmission circuit of FIG. 20 as an eleventh embodiment of the present invention.

FIG. 24 is a diagram showing a configuration in which one branch circuit is omitted from the optical transmission circuit of FIG. 20 as a twelfth embodiment of the present invention.

25 is a diagram showing a configuration in which a differential amplifier is further omitted from the optical transmission circuit of FIG. 24 as a thirteenth embodiment of the present invention.

FIG. 26 is a diagram showing the configuration of an optical transmission circuit using a 6-electrode push-pull electrode type Mach-Zehnder interferometer type optical intensity modulator as the 14th embodiment of the present invention.

[Description of Reference Signs] 1 2-electrode push-pull electrode type Mach-Zehnder interferometric optical intensity modulator 2 2-electrode Mach-Zehnder interferometric optical intensity modulator 3 3-electrode Mach-Zehnder interferometric optical intensity modulator 4 4-electrode push-pull electrode -Type Mach-Zehnder interferometric light intensity modulator 5 2-electrode optical phase modulator 6 6-electrode push-pull electrode-type Mach-Zehnder interferometric light intensity modulator 7 ₁ , 7 ₂ Arm 8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ , 8 ₅ and 8 ₆ Electrodes 9 Optical input port 10 Optical input port 11 Optical branching unit 12 Optical multiplexing unit 13 Light sources 14 ₁ and 14 ₂ Driving circuit (prior art) 15 Electrical data signal 16 Logical inversion signal 17 of electrical data signal 15 Optical data signals 18 ₁ , 18 ₂ Electrical data signals actually applied to electrodes (prior art) 19 ₁ , 19 ₂ , 19 ₃ , 19 ₄ , 19 ₅ , 19 ₆ Electrical filters 20 ₁ , 20 ₂ , 20 ₃ , 20 ₄ , 20 ₅ , 20 ₆ Electrical data signals 21 ₁ , 21 ₂ , 21 ₃ , 21 ₄ , 21 ₅ , 21 ₆ Drive circuits 22 ₁ , 22 actually applied to the electrodes after passing through the electrical filter ₂ Pass band characteristic 23 Base materials 24 ₁ and 24 ₂ Gain adjusting circuits 25 ₁ , 25 ₂ , 25 ₃ , 25 ₄ and 25 ₅ Phase adjusting circuit 26 Bias applying circuit 27 Optical amplifiers 28 ₁ and 28 ₂ Electrical input terminal 29 Optical output Terminal 30 Differential amplifier 31 ₁ , 31 ₂ Differential electrical signal 32 ₁ , 32 ₂ 2 Branch circuit 33 ₁ , 33 ₂ , 33 ₃ , 33 ₄ 2 branched electrical data signal 34 Frequency division circuit 34 a, 34 b, 34 c Frequency division Circuit input port, first output port, second output port 35 ₁ , 35 ₂ Frequency-divided electrical data signals 36 ₁ , 36 ₂ Frequency-division circuit pass band characteristics 37 ₁ , 37 ₂ 3-branch circuits 38 ₁ , 38 ₂ Three _3, 38 _4, 38 _5, 38 ₆ 3
Branched electrical data signals 39 ₁ , 39 ₂ , 39 ₃ Passband characteristics 40 ₁ , 40 ₂ , 40 ₃ , 40 ₄ Passband characteristics

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 10/152 (72) Inventor Shoichiro Kuwahara 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Incorporated (72) Inventor Yoshiaki Kisaka 2-3-1, Otemachi, Chiyoda-ku, Tokyo F-Term (Reference), Nihon Telegraph and Telephone Corporation 2H079 AA02 AA12 BA01 CA04 DA03 EA05 EB04 EB15 FA03 5K102 AA15 AH02 AH26 AH27 PH02 RD05 RD11

Claims (14)

[Claims] 1. A light source for generating continuous light, a branching unit for branching an input electric signal into an integer N of 2 or more, and N electrodes, and an interference amount depending on each voltage of the electrodes. An interfering optical intensity modulator that changes, an electric filter having N different pass frequency bands, and N driving circuits are provided, and when the pass frequency bands of the N electric filters are superposed,
The entire pass frequency band substantially includes the signal frequency band of the input electric signal, and each of the electric signals branched by the branching unit passes through the electric filter one by one, all of which are before and after the electric filter. An optical transmission circuit which is applied to an electrode of the interferometric light intensity modulator via the drive circuit regardless of the above, and generates a light intensity modulation signal corresponding to the input electric signal from the continuous light. 2. A light source for generating continuous light, a branching unit for branching an input electric signal into an integer N of 2 or more, an optical phase modulator having N electrodes, and N different pass frequency bands. An electric filter and N driving circuits are provided. When the pass frequency bands of the N electric filters are superposed, the entire pass frequency band substantially includes the signal frequency band of the input electric signal, and the branch Each of the electric signals branched by the means passes through the electric filter one by one, and all of them are applied to the electrodes of the optical phase modulator via the drive circuit without passing through the electric filter, and the continuous electric signals An optical transmitter circuit for generating an optical phase modulation signal corresponding to the input electric signal from light. 3. A light source for generating continuous light, a push-pull electrode type Mach-Zehnder interferometric light intensity modulator having N / 2 electrodes on each of two arms, and two differential signals corresponding to an input electric signal. A differential amplifier that outputs an electric signal, N electric filters, and N drive circuits are provided.
Is 2, and when the pass frequency bands of the N electrical filters are superposed, the total pass frequency band substantially includes the signal frequency band of the input electrical signal, and the two differential electrical frequencies of the differential amplifier are The signals respectively pass through the electrical filter, all of which are applied to the electrodes of the light intensity modulator via the drive circuit, before and after the electrical filter, and correspond to the input electrical signal from the continuous light. An optical transmitter circuit characterized by generating a light intensity signal. 4. A light source for generating continuous light, and when N is an integer of 3 or more, one of the two arms has one arm.
Mach-Zehnder interferometer type optical intensity modulator having N-1 electrodes on the other arm, and a differential amplifier for outputting two differential electrical signals corresponding to the input electrical signal. , N is provided with branching means for branching one of the two differential electric signals of the differential amplifier into N−1 electric filters having different pass frequency bands, and N driving circuits,
When the pass frequency bands of the electric filters are superposed, the total pass frequency band substantially includes the signal frequency band of the input electric signal, and the other one of the two differential electric signals of the differential amplifier is It passes through one of the electric filters and is applied to one electrode of the one arm of the light intensity modulator via one of the driving circuits before and after the electric filter, and the branching is performed. The N-1 electrical signals branched into N-1 by the means respectively pass the remaining N-1 electrical filters, all of which remain before and after the electrical filter. The light intensity signal corresponding to the input electric signal is generated from the continuous light by being applied to N-1 electrodes on the other arm of the light intensity modulator via the drive circuit. Optical transmitter circuit. 5. A light source for generating continuous light, and when M is an integer of 2 or more and N is an integer of M + 2 or more, one of the two arms has M electrodes and the other one Mach-Zehnder interferometer type optical intensity modulator having N-M electrodes on its arm, a differential amplifier for outputting two differential electrical signals corresponding to input electrical signals, and two differential electrical circuits of the differential amplifier. First branching means for branching one of the signals into M pieces;
The other one of the two differential electric signals of the differential amplifier is N-
The second branching means for branching into M pieces, the N electric filters having different pass frequency bands, and the N drive circuits are provided. When the pass frequency bands of the N electric filters are overlapped, the entire pass frequency is obtained. The band substantially includes the signal frequency band of the input electric signal, and the electric signals branched into M pieces by the first dividing means respectively pass through the M electric filters, all of which are before and after the electric filter. NM, which is applied to M electrodes on the one arm of the light intensity modulator via M driving circuits, and is branched to NM by the second branching means. Electrical signals each pass through the remaining N-M electrical filters, all of which pass through the remaining NM driving circuits before and after the electrical filter. The other one The optical transmitter circuit is applied to the N-M number of electrodes, and generates a light intensity signal corresponding to the input electrical signal from the continuous light in. 6. The optical transmission circuit according to claim 5,
An optical transmission circuit, wherein N is twice M. 7. The optical transmission circuit according to claim 3, wherein the differential amplifier is deleted, and the input electric signal and its inverted signal are converted into two differential electric signals of the differential amplifier, respectively. An optical transmission circuit characterized by being replaced. 8. The optical transmission circuit according to claim 1, wherein the N electric filters are one low-pass filter, N−2 band-pass filters, and one high-pass filter. An optical transmission circuit characterized by. 9. The optical transmission circuit according to claim 1, wherein the N electric filters are one low-pass filter and N−1 band-pass filters. circuit. 10. The optical transmission circuit according to claim 1, wherein the N electrical filters are N−1 bandpass filters and one highpass filter. circuit. 11. The optical transmission circuit according to claim 1, wherein the N electrical filters are all bandpass filters. 12. The optical transmission circuit according to claim 1, wherein N is 2, the two electric filters are one low-pass filter and one high-pass filter, and these two electric filters are provided. An optical transmission circuit, wherein: and the branching means are realized by one frequency division circuit. 13. The optical transmission circuit according to claim 1, wherein at least one of the N driving circuits has a gain adjusting function and a voltage amplitude of an electric signal applied to each electrode is changed. An optical transmission circuit which is adjusted to flatten the frequency characteristic of the optical transmission circuit. 14. The optical transmission circuit according to claim 1, further comprising a phase adjustment circuit that adjusts a phase between electric signals applied to each electrode.