JP3494426B2 - FM modulator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM modulator, and more particularly to an FM modulator that uses a semiconductor laser to generate an FM modulated signal.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a configuration of a conventional FM modulator. In FIG. 5, the FM modulator is
A signal source 501, an FM modulation laser (hereinafter referred to as an FM laser) 502, a first optical waveguide section 503, a local light source 504, a second optical waveguide section 505, and a photodetection section 506 are provided. ing.

In the FM modulator constructed as described above, the signal source 501 outputs an electric signal which is an original signal to be FM-modulated. The FM laser 502 is composed of, for example, a semiconductor laser, oscillates light having a wavelength λ1 under a condition where the injection current is constant, and when the injection current is amplitude-modulated, the oscillation wavelength (optical frequency) is also modulated, and the wavelength λ1 is centered. The optical frequency modulated signal is output. The first optical waveguide unit 503 guides the optical signal output from the FM laser 502. The local light source 504 outputs light having a wavelength λ0 which differs from the oscillation wavelength λ1 of the FM laser 502 by a predetermined amount Δλ. The second optical waveguide unit 505 guides the unmodulated light from the local light source 504.
The two lights guided by the first optical waveguide unit 503 and the second optical waveguide unit 505 are combined and input to the optical detection unit 506. The optical detection unit 506 is composed of a photodiode or the like having a squared detection characteristic, and when two lights of different wavelengths are input, a property of generating beat components of the two lights at a frequency corresponding to the wavelength difference. (This operation is called heterodyne detection), and the output optical signal from the FM laser 502 guided by the first optical waveguide section 503 and the local light source 504 guided by the second optical waveguide section 505. The beat signals of these two lights are output at the frequency corresponding to the wavelength difference Δλ from the output light of the above.

The beat signal obtained as described above is
This is an FM modulation signal that uses the output signal from the signal source 501 as an original signal, and by using appropriate ones for the FM laser 502 and the local oscillation light source 504, F
It is possible to easily generate a very high frequency and wide band FM modulation signal having a center frequency (carrier frequency) of several GHz or more and a frequency shift amount of several 100 MHz or more, which is difficult to realize with the M modulator. The FM demodulated signal obtained by demodulating the FM modulated signal due to the expansion of the frequency shift amount has a high C
NR (Carrier to Noise Power Ratio).

FIG. 6 shows an example of the overall configuration of a transmission device including the FM modulator shown in FIG. Literature (eg K.Ki
kushima, et al., "Optical super wide-band FM modul
ation scheme and its application to multi-channel
AM video transmission systems ", IOOC'95, PD2-7,
As described in 1995.), this transmission device is shown in FIG.
The broadband FM modulation signal generated in the FM modulator 601 as described above is converted into a light intensity modulation signal by the transmission laser 603 included in the optical transmission unit 602, and then the light intensity modulation is performed using the optical transmission line 604. Transmit signal. The transmission device reconverts the optical intensity modulation signal received by the optical receiving unit 605 into an FM modulation signal, and then the FM demodulation circuit 60.
It demodulates to the original electric signal by 7. FM demodulation circuit 60
Reference numeral 7 denotes a differential detection type FM demodulator, and an identifying unit 608 identifies the FM modulated signal input from the optical receiving unit 605 with a predetermined threshold value Vref and converts it into a pulse signal (logical signal). Further, the identification unit 608 has two output ports, one output signal is directly applied, and the other output signal is given a predetermined delay amount in the delay unit 609.
It is input to the multiplication unit 610. The multiplication unit 610 creates a logical product signal (pulse signal) of both pulse signals. When the filter 611 passes only the low frequency component of the pulse signal and outputs the pulse signal, the amplitude variation component of the output signal uniquely corresponds to the frequency variation component of the input FM modulation signal,
This demodulates the FM modulated signal. Identification unit 608
By using a logic element (such as an AND gate) for high-speed signal processing in the multiplication unit 610, it is possible to easily demodulate the high frequency and wide band FM modulated signal generated in the configuration of FIG.

By the way, it is generally known that in an FM modulated signal transmission apparatus, the group delay characteristic of the transmission path within the band of the FM modulated signal affects the quality of the transmitted signal. For example, as shown in FIG. 7A, when the frequency characteristic of the group delay amount changes relatively gently within the band, low-order distortion components such as second-order and third-order are generated, and As shown in (b), when the group delay amount fluctuates in a ripple shape having fine peaks and troughs in the band, there are literatures (for example, Ishii et al .; “Group delay distortion in a broadband FM modulation type optical video transmission system” Theoretical study ”, IEICE Technical Report O
CS96-17, 1996. Etc.), higher-order distortion of the fourth order or higher occurs, which deteriorates the transmission signal quality. Particularly for the latter high-order distortion, it is difficult to apply a distortion reduction technique such as a distortion compensation technique, and it is necessary to sufficiently suppress the in-band ripple of the group delay in advance.
However, the group delay characteristic is almost always caused by the impedance mismatch between the components used in the transmission line or within the components, and it is very difficult to eliminate them.

Next, the FM demodulation circuit 607 described with reference to FIG.
8A shows a measurement example of the input frequency vs. output signal level (f-V characteristic) of FIG. 8A, showing the difference (Δ output voltage) between the approximate value and the true value when the f-V characteristic is linearly approximated. 8 (b). From the viewpoint of waveform distortion of the demodulated signal, f− of the FM demodulation circuit
It is desirable that the V characteristic is also linear, but FIG.
As can be seen from (b), it has a fine ripple, which also causes a high-order distortion and deteriorates the quality of the transmission signal.

As described above, in the FM modulation signal transmission apparatus, the non-linearity in the group delay characteristic of the transmission line and the FM demodulation characteristic affects the quality of the transmission signal. Particularly, in the wideband FM modulated signal transmission apparatus described with reference to FIGS. 5 to 8, since the transmission signal has a band of several GHz, the peaks and valleys of ripples in the band in the group delay characteristic and the FM demodulation characteristic. Also becomes very large, higher order distortion is generated, and the quality of the transmission signal is greatly deteriorated.

[0009]

As described above, in the case of transmitting a wide band FM modulation signal generated by an FM modulation device using the optical frequency modulation operation of a semiconductor laser and heterodyne detection, the CNR is changed by a large frequency shift amount. While it can be improved, since the FM modulation signal spreads over a very wide band, the group delay characteristic of the transmission line and the demodulation characteristic of the FM demodulator in the band fluctuate in a ripple shape having a large number of peaks and valleys. There is a problem in that higher-order distortion is largely generated and the quality of the transmission signal is deteriorated.

Therefore, an object of the present invention is to eliminate the ripples in the group delay characteristic and the FM demodulation characteristic of the transmission line, which are affected by the optical frequency modulation operation of the semiconductor laser and the broadband FM modulation signal generated by using the heterodyne detection. An object of the present invention is to provide an FM modulator that can substantially smooth and reduce high-order distortion.

[0011]

SUMMARY OF THE INVENTION A first invention is a device for generating a wide band FM modulation signal, wherein a first signal source for outputting a first electric signal and an input electric signal are provided. It has the property of oscillating light of wavelength λ1 in a steady state that does not change and uniquely converting the amplitude change of the input electric signal into the change of the optical frequency. The first electric signal supplied as the input electric signal is the optical signal. A laser for FM modulation (hereinafter referred to as an FM laser) that is converted to and output, a second signal source that outputs a second electric signal that is uncorrelated to the first electric signal, and a change in the input electric signal. A second one which has a property of being uniquely converted into a change in optical phase and is supplied as the input electric signal
The external optical modulator for optical phase-modulating the output optical signal from the FM laser with the electric signal, and the first optical waveguide for guiding the output optical signal from the external optical modulator, and the oscillation wavelength λ1 of the FM laser When two lights of different wavelengths are input due to the square-law detection characteristic, the local light source that outputs the light of wavelength λ 0 that differs by Δλ, and the second optical waveguide that guides the output light from the local light source. Has a property of generating beat components of the two lights at a frequency corresponding to the wavelength difference, and outputs the output optical signal from the external optical modulator guided by the first optical waveguide and the second optical waveguide. And a light detection unit that inputs the output light from the local light source guided by the unit and outputs the beat component of the two lights at a frequency corresponding to the wavelength difference Δλ between them.

A broadband FM modulation signal generated by generating an optical frequency modulation signal by modulating the injection current of the FM laser and performing heterodyne detection of the optical frequency modulation signal is
High-order distortion is generated during demodulation due to the ripple of the group delay characteristic of the transmission line and the FM demodulation characteristic. Therefore, in the first aspect of the invention, the optical frequency modulation signal output from the FM laser is further subjected to the optical phase modulation uncorrelated with the optical frequency modulation signal from the FM laser by using the external optical modulator. Realizes an FM modulator that substantially smoothes the ripple of the group delay characteristic and the FM demodulation characteristic, suppresses the higher-order distortion that should occur due to these, and suppresses the waveform deterioration due to the characteristics of the transmission line and the FM demodulation circuit. can do.

A second invention is an apparatus for generating a wide band FM modulation signal, which comprises a first signal source for outputting a first electric signal and a light having a wavelength λ1 in a steady state where the input electric signal does not change. An FM modulation laser that oscillates and has a property of uniquely converting an amplitude change of an input electric signal into a change of an optical frequency, and converting a first electric signal supplied as the input electric signal into an optical signal and outputting the optical signal. (Hereinafter, referred to as FM laser), a first optical waveguide section that guides an output optical signal from the FM laser, and a second signal source that outputs a second electric signal that is uncorrelated with the first electric signal. , FM laser oscillation wavelength λ1 and △
A local light source that outputs light of wavelength λ 0 that differs by λ and a characteristic that uniquely converts a change in the input electric signal into a change in the optical phase, and uses the second electric signal supplied as the input electric signal to generate the local light. An external light modulator for optically phase-modulating the output light from the light source and outputting it, a second optical waveguide for guiding the output optical signal from the external light modulator, and two lights of different wavelengths due to the square-law detection characteristic. Has a property of generating a beat component of the two lights at a frequency corresponding to the wavelength difference, and the output optical signal from the FM laser guided by the first optical waveguide unit and the second optical signal. And an output optical signal from the external optical phase modulator guided by the optical waveguide section of the optical waveguide section and outputs a beat component of the two lights at a frequency corresponding to the wavelength difference Δλ between them. .

In the second invention, the output optical signal from the external optical phase modulator uncorrelated with the optical frequency modulation signal from the FM laser is multiplexed, so that the same as in the first invention,
F that substantially smoothes the ripple of the group delay characteristic and the FM demodulation characteristic, suppresses the higher-order distortion that should occur due to these, and suppresses the waveform deterioration due to the characteristics of the transmission line and the FM demodulation circuit.
An M modulator can be realized.

A third invention is an apparatus for generating a wide band FM modulated signal, which comprises a first signal source for outputting a first electric signal and a light of wavelength λ1 in a steady state where the input electric signal does not change. An FM modulation laser that oscillates and has a property of uniquely converting an amplitude change of an input electric signal into a change of an optical frequency, and converting a first electric signal supplied as the input electric signal into an optical signal and outputting the optical signal. (Hereinafter, referred to as FM laser), a first optical waveguide section that guides an output optical signal from the FM laser, and a second signal source that outputs a second electric signal that is uncorrelated with the first electric signal. , In the steady state where the input electric signal does not change, it oscillates light having a wavelength λ0 different from the oscillation wavelength λ1 of the FM laser by Δλ, and has a property of uniquely converting the amplitude change of the input electric signal into the change of the optical frequency. Supplied as input electrical signal A local light source that converts the electrical signal of 2 into an optical signal and outputs the optical signal, a second optical waveguide that guides the output optical signal from the local light source, and two lights of different wavelengths are input due to the square-law detection characteristic. In this case, the output optical signal from the FM laser guided by the first optical waveguide section and the second optical waveguide have the property of generating the beat components of the two lights at a frequency corresponding to the wavelength difference. And an optical detection unit for inputting the output optical signal from the local light source guided by the unit and outputting the beat components of the two lights at a frequency corresponding to the wavelength difference Δλ between them.

In the third aspect of the invention, the group delay characteristic and the FM are generated in the same manner as in the first aspect of the invention by multiplexing the output optical signal from the local light source that is uncorrelated with the optical frequency modulation signal from the FM laser. Ripple of the demodulation characteristics is substantially smoothed to suppress the higher-order distortion that would otherwise be caused by them, and
It is possible to realize an FM modulator that suppresses waveform deterioration due to the characteristics of the M demodulation circuit.

A fourth invention is an apparatus for generating a wide band FM modulated signal, which comprises a first signal source for outputting a first electric signal and a second electric signal uncorrelated to the first electric signal. A second signal source for outputting the first electric signal and a second electric signal for combining and outputting the first electric signal and the second electric signal, and oscillates light of wavelength λ1 in a steady state in which the input electric signal does not change. An FM modulation laser (hereinafter referred to as an FM laser) having a property of uniquely converting an amplitude change of an input electric signal into a change of an optical frequency and converting an electric signal output from a multiplexing unit into an optical signal and outputting the optical signal. ), A first optical waveguide for guiding an output optical signal from the FM laser, a local light source for outputting light of a wavelength λ0 different from the oscillation wavelength λ1 of the FM laser by Δλ, and an output light from the local light source. The second optical waveguide that guides the
When two lights of different wavelengths are input, it has a property of generating a beat component of the two lights at a frequency corresponding to the wavelength difference, and is emitted from the FM laser guided by the first optical waveguide unit. The output optical signal and the output light from the local light source guided by the second optical waveguide unit are input, and their wavelength difference Δ
and a photodetector that outputs beat components of the two lights at a frequency corresponding to λ.

In the fourth aspect of the present invention, the first electric signal and the second electric signal uncorrelated are multiplexed and added to the FM laser.
By performing optical frequency modulation using the optical frequency modulation operation of the FM laser, the ripples of the group delay characteristic and the FM demodulation characteristic are substantially smoothed as in the first invention, and should be generated by these. Higher-order distortion is suppressed, and transmission lines and F
It is possible to realize an FM modulator that suppresses waveform deterioration due to the characteristics of the M demodulation circuit.

A fifth invention is characterized in that, in any one of the first to fourth inventions, the frequency of the second electric signal is higher than the frequency of the first electric signal. In the fifth invention, the second electric signal is set to a higher frequency than the first electric signal to be originally transmitted, and the ripple of the group delay characteristic and the FM demodulation characteristic in the first to fourth inventions is substantially set. Make the smoothing effect more clear.

A sixth invention is characterized in that, in any one of the first to fourth inventions, the frequency of the second electric signal is larger than twice the frequency of the first electric signal. In the sixth aspect of the invention, the frequency of the second electric signal is set to be greater than twice the frequency of the first electric signal to be originally transmitted, and the second electric signal is generated by the interaction between the first electric signal and the second electric signal. The distortion component is prevented from becoming an interfering wave with respect to the first electric signal, and the group delay characteristics and F in the first to fourth inventions are avoided.
The substantial smoothing effect of the ripple of the M demodulation characteristic will be made clearer.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION F according to the first embodiment of the present invention
The M modulator will be described with reference to FIG. 1 showing its components and connection modes. In FIG. 1, the FM modulator includes a first signal source 101 as its constituent elements,
A laser for FM modulation (hereinafter, FM laser) 102, and a first
Optical waveguide unit 103, local light source 104, second optical waveguide unit 105, optical detection unit 106, and second signal source 107.
And an external optical phase modulator 108.

Next, the connection mode and operation of the FM modulator shown in FIG. 1 will be described. The first signal source 101 outputs a first electric signal which is an original signal to be FM-modulated. The FM laser 102 is typically composed of a semiconductor laser, which oscillates light having a wavelength λ1 under the condition of a constant injection current.
When the injection current is amplitude-modulated by the electric signal of 1, the oscillation wavelength (optical frequency) is also modulated and an optical frequency modulation signal centered on the wavelength λ1 is output. The second signal source 107 is the first
The second optical signal that is uncorrelated to the electric signal of 1 is output, and the external optical phase modulator 108 performs optical phase modulation on the output optical signal from the FM laser 102 using the second electric signal.
The first optical waveguide section 103 guides the optical signal output from the external optical modulation section 108. The local light source 104 has a wavelength λ different from the oscillation wavelength λ 1 of the FM laser 102 by a predetermined amount Δλ.
Outputs 0 light. The second optical waveguide section 105 guides the unmodulated light from the local light source 104. The two lights guided by the first optical waveguide unit 103 and the second optical waveguide unit 105 are combined and input to the optical detection unit 106. Optical detection unit 10
6 performs heterodyne detection based on its squared detection characteristic, and at the frequency corresponding to the wavelength difference Δλ between the output optical signal from the external optical phase modulator 108 and the output light from the local light source 104, Output a beat signal. This beat signal is a wideband FM modulation signal that uses the first electric signal and the second electric signal as original signals.

FIG. 2 shows an F according to the second embodiment of the present invention.
It is a block diagram which shows the structure of an M modulator. In FIG. 2, the FM modulator has the same components as those of the first embodiment, and therefore the same reference numerals are given to the corresponding components. However, since the connection modes are different between the first and second embodiments, the operation of the FM modulator according to the second embodiment will be described below centering on this difference, which is clear from the first embodiment. A description of such points is omitted. The first optical waveguide unit 103 guides the optical signal output from the FM laser 102 to the optical detection unit 106. External optical phase modulator 108
Performs optical phase modulation on the unmodulated light from the local light source 104 by the second electric signal. Second optical waveguide section 105
Guides the optical signal output from the external optical phase modulator 108 to the photodetector 106. The optical detector 106 outputs the beat signals of the two lights at a frequency corresponding to the wavelength difference Δλ between the output optical signal from the FM laser 102 and the output optical signal from the external optical phase modulator 108.

FIG. 3 shows an F according to the third embodiment of the present invention.
It is a block diagram which shows the structure of an M modulator. In FIG. 3, the FM modulator differs from the FM modulator in the second embodiment only in that the external optical phase modulator 108 is not provided.
Corresponding components are given the same reference numbers. Furthermore, the second
Since the connection mode is also different between the third embodiment and the third embodiment, hereinafter, the F according to the third embodiment will be focused on these differences.
The operation of the M modulator will be described, and the description of points that are apparent from the second embodiment will be omitted. The local oscillation light source 104 is typically composed of a semiconductor laser, which oscillates light having a wavelength λ 0 under the condition that the injection current is constant and amplitude-modulates the injection current by the second electric signal. ) Is also modulated and outputs an optical frequency modulation signal centered on the wavelength λ 0. The second optical waveguide section 105 guides the optical signal output from the local light source 104. The optical detection unit 106 outputs the beat signal of the two lights at a frequency corresponding to the wavelength difference Δλ between the output optical signal from the FM laser 102 and the output light from the local light source 104.

In the first to third embodiments described above, the second electric signal is a signal that is uncorrelated with the first electric signal to be originally transmitted. While not affecting the signal quality during demodulation,
The periodic fine ripples in the group delay characteristic and the FM demodulation characteristic of the FM modulated signal on the transmission path are substantially smoothed to suppress the waveform distortion at the time of demodulation of the wide band FM modulated signal. Further, in particular, in the third embodiment, the second electric signal is directly supplied to the local light source 104, so that the external optical phase required in the first and second embodiments is required. Since the modulator 108 is not required, the FM modulator can be easily configured and its manufacturing cost can be reduced.

FIG. 4 shows an F according to the fourth embodiment of the present invention.
It is a block diagram which shows the structure of an M modulator. In FIG. 4, the FM modulator is different from that of the first embodiment only in that a multiplexing unit 109 is provided instead of the external optical phase modulator 108. Therefore, the same reference numerals are given to corresponding components. . Furthermore, since the connection modes are also different in the first and fourth embodiments, the fourth embodiment will be described below focusing on these differences.
The operation of the FM modulator according to the first embodiment will be described, and the description of points that are apparent from the first embodiment will be omitted. Multiplexing part 10
Reference numeral 9 multiplexes a first electric signal and a second electric signal which are uncorrelated to each other and inputs them to the FM laser 102. FM
The laser 102 amplitude-modulates the injection current with the electric signal output from the multiplexing unit 109, and outputs an optical frequency modulation signal centered on the wavelength λ1. First optical waveguide 103
Guides the optical signal output from the FM laser 102 to the optical detection unit 106. The optical detection unit 106 outputs the beat signal of the two lights at a frequency corresponding to the wavelength difference Δλ between the output optical signal from the FM laser 102 and the output light from the local light source 104.

Here, as in the first to third embodiments, the second electric signal is a signal uncorrelated to the first electric signal to be originally transmitted, so that the first electric signal is transmitted. A wide band FM modulation signal by substantially smoothing periodic fine ripples in the group delay characteristic of the transmission line and the fV characteristic of the FM demodulation circuit without affecting the signal quality at the time of signal transmission and demodulation. Suppresses waveform distortion during demodulation of. However, in the fourth embodiment, both the first electric signal and the second electric signal that are uncorrelated to each other are input to the FM laser 102, so that the total of the optical modulation degrees does not exceed 100%. It is necessary to set the input level of the signal to the FM laser 102.

An FM modulator according to the fifth embodiment of the present invention will be described. Since the constituent elements of the present FM modulator are the same as those of any of the first to fourth embodiments, the description of the connection mode and operation will be omitted. In the present embodiment, the second electric signal is uncorrelated with the first electric signal, and its frequency is set to a higher frequency than that of the first electric signal. As a result, the group delay characteristic of the transmission line and the F
The substantial smoothing effect of the second electric signal on the periodic fine ripples in the demodulation characteristics of the M demodulation circuit is improved as compared with that of the first to fourth embodiments. Further, this smoothing effect improves as the frequency of the second electric signal increases.

An FM modulator according to the sixth embodiment of the present invention will be described. Since the constituent elements of the present FM modulator are the same as those of any of the first to fourth embodiments, the description of the connection mode and operation will be omitted. In the present embodiment, the second electric signal is uncorrelated with the first electric signal, and the frequency thereof is set to be larger than twice the frequency of the first electric signal. Thereby, even when the occupied band of the first electric signal is wide, the second-order intermodulation distortion between the first and second electric signals is prevented from occurring within the occupied band of the first electric signal, In addition, the substantial smoothing effect of the second electric signal with respect to periodic fine ripples in the group delay characteristic of the transmission line and the demodulation characteristic of the FM demodulation circuit is
It is improved over that of the first to fourth embodiments. Further, this smoothing effect improves as the frequency of the second electric signal increases.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an FM modulator according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an FM modulator according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an FM modulator according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an FM modulator according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional FM modulator.

FIG. 6 is a diagram for explaining a configuration of a transmission system of a wideband FM modulated signal generated by an FM modulator.

FIG. 7 is a schematic diagram for explaining a group delay characteristic of an optical transmission line.

FIG. 8 is a diagram for explaining ripples in the FM demodulation characteristic (fV characteristic) of the FM demodulation circuit.

[Explanation of symbols]

101 ... First signal source 102 ... FM modulation laser (FM laser) 103 ... First optical waveguide 104 ... Local light source 105 ... Second optical waveguide 106 ... Optical detection unit 107 ... Second signal source 108 ... External light modulator 109 ... Combiner

Front Page Continuation (72) Inventor Seiichiro Kawashima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Telephone Corporation (56) References JP-A-8-274714 (JP, A) JP-A-10-313276 (JP, A) JP-A-6-261005 (JP, A) Yoshikazu Ishii et al., Wide band FM modulation type Theoretical study on group delay distortion in optical image transmission system, IEICE Technical Report, Japan, The Institute of Electronics, Information and Communication Engineers, June 25, 1996, Vol. 96, No. 132 (CS96-40), pp. 1-6 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 JISST file (JOIS)

Claims (6)

(57) [Claims] 1. A device for generating a wide band FM modulation signal, comprising: a first signal source for outputting a first electric signal; and a light source for oscillating light of wavelength λ1 in a steady state in which the input electric signal does not change, An FM modulation laser that has a property of uniquely converting an amplitude change of an electric signal into a change of an optical frequency, and converts the first electric signal supplied as the input electric signal into an optical signal and outputs the optical signal (hereinafter, referred to as FM laser), a second signal source that outputs a second electric signal that is uncorrelated to the first electric signal, and a property that uniquely converts a change in the input electric signal into a change in the optical phase. The second electrical signal supplied as the input electrical signal.
Of the FM laser, an external optical modulator that optically phase-modulates and outputs the output optical signal from the FM laser by the electric signal, a first optical waveguide that guides the output optical signal from the external optical modulator, Wavelength λ that differs from the oscillation wavelength λ1 by Δλ
A local light source that outputs 0 light, a second optical waveguide that guides the output light from the local light source, and a wavelength difference when two lights of different wavelengths are input due to the square-law detection characteristic. By the output optical signal from the external optical modulator guided by the first optical waveguide and the second optical waveguide. An FM modulator, comprising: a guided output light from the local light source, and a photodetector that outputs a beat component of the two lights at a frequency corresponding to a wavelength difference Δλ between them. 2. A device for generating a wide band FM modulation signal, comprising: a first signal source for outputting a first electric signal; and a light source for oscillating light having a wavelength λ1 in a steady state where the input electric signal does not change, An FM modulation laser that has a property of uniquely converting an amplitude change of an electric signal into a change of an optical frequency, and converts the first electric signal supplied as the input electric signal into an optical signal and outputs the optical signal (hereinafter, referred to as An FM laser), a first optical waveguide section that guides an output optical signal from the FM laser, and a second signal source that outputs a second electrical signal that is uncorrelated to the first electrical signal, A wavelength λ different from the oscillation wavelength λ1 of the FM laser by Δλ
The local light source that outputs 0 light and the second light source that has the property of uniquely converting a change in the input electric signal into a change in the optical phase and is supplied as the input electric signal.
An external optical modulator for optically phase-modulating the output light from the local light source by the electric signal of 1., a second optical waveguide for guiding the output optical signal from the external optical modulator, and a square-law detection characteristic. When two lights of different wavelengths are input, the FM guided by the first optical waveguide section has a property of generating a beat component of the two lights at a frequency corresponding to the wavelength difference. The output optical signal from the laser and the output optical signal from the external optical phase modulator guided by the second optical waveguide are input, and their wavelength difference Δλ.
And an optical detection unit that outputs the beat components of the two lights at a frequency corresponding to. 3. A device for generating a wide band FM modulation signal, comprising: a first signal source for outputting a first electric signal; and a light source of oscillating light of wavelength λ1 in a steady state where the input electric signal does not change, An FM modulation laser that has a property of uniquely converting an amplitude change of an electric signal into a change of an optical frequency, and converts the first electric signal supplied as the input electric signal into an optical signal and outputs the optical signal (hereinafter, referred to as An FM laser), a first optical waveguide section that guides an output optical signal from the FM laser, and a second signal source that outputs a second electrical signal that is uncorrelated to the first electrical signal, In a steady state in which the input electric signal does not change, it has a property of oscillating light having a wavelength λ0 different from the oscillation wavelength λ1 of the FM laser by Δλ and uniquely converting an amplitude change of the input electric signal into a change of the optical frequency. Supplied as input electrical signal A local light source that converts the second electric signal into an optical signal and outputs the optical signal; a second optical waveguide that guides the output optical signal from the local light source; and two different wavelengths depending on the square-law detection characteristic. When light is input, it has a property of generating beat components of the two lights at a frequency corresponding to the wavelength difference, and is an output optical signal from the FM laser guided by the first optical waveguide unit. And an output optical signal from the local light source guided by the second optical waveguide unit, and outputs a beat component of the two lights at a frequency corresponding to a wavelength difference Δλ between them. And an FM modulator comprising: 4. A device for generating a wideband FM modulated signal, which outputs a first signal source for outputting a first electric signal and a second electric signal uncorrelated to the first electric signal. A second signal source, a multiplexer for multiplexing and outputting the first electric signal and the second electric signal, and oscillating light of wavelength λ1 in a steady state in which the input electric signal does not change, An FM modulation laser (hereinafter referred to as an FM laser) that has a property of uniquely converting an amplitude change of an input electric signal into a change of an optical frequency, and converts an electric signal output from the multiplexing unit into an optical signal and outputs the optical signal. ), A first optical waveguide for guiding an output optical signal from the FM laser, and a wavelength λ different from the oscillation wavelength λ 1 of the FM laser by Δλ.
A local light source that outputs 0 light, a second optical waveguide that guides the output light from the local light source, and a wavelength difference when two lights of different wavelengths are input due to the square-law detection characteristic. Has a property of generating the beat components of the two lights at a frequency corresponding to, and outputs the output optical signal from the FM laser guided by the first optical waveguide and the optical signal output by the second optical waveguide. And an optical detection unit that inputs the output light from the local light source and outputs the beat component of the two lights at a frequency corresponding to the wavelength difference Δλ between them. 5. The frequency of the second electric signal is higher than the frequency of the first electric signal.
The FM modulator according to claim 1. 6. The FM modulator according to claim 1, wherein the frequency of the second electric signal is greater than twice the frequency of the first electric signal.