JP3276052B2 - Optical transmission device and optical transmission system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission apparatus capable of coping with a longer transmission distance and a higher transmission speed, and an optical transmission system using the same.

[0002]

2. Description of the Related Art In an optical transmission system, an intensity modulation-direct detection system (hereinafter referred to as an "IM-DD system") is the simplest transmission system. In an optical transmission system using an optical fiber having a large chromatic dispersion (existing 1.3 μm zero-dispersion fiber) as a transmission line, the transmission distance and the transmission speed are greatly limited by the chromatic dispersion. The signal degradation due to the chromatic dispersion depends on the spectrum spread of the signal. Therefore, by using a Mach-Zehnder interferometer type (hereinafter referred to as "MZ type") light intensity modulator as an external modulator instead of the direct modulation of the semiconductor laser, it is possible to suppress the excessive spread of the signal spectrum and reduce the transmission distance. Can be extended. The MZ light intensity modulator is manufactured using LiNbO ₃ or a semiconductor. However, in high-speed optical transmission at 10 Gb / s or more, the transmission distance is limited to about several tens km due to chromatic dispersion even if an MZ-type optical intensity modulator is used due to the spread of the spectrum of the optical signal itself.

As a means for overcoming the limitation due to chromatic dispersion, an optical transmission system using duobinary signal light has been proposed (K. Yonnaga et al., Electron. Lett., Vo.
l. 31, pp. 302-304, 1995). FIG. 11 shows a configuration example of a conventional optical duobinary transmission system. In the figure, a binary data signal to be transmitted is a duobinary encoding circuit 7.
At 0, it is converted into a ternary duobinary signal. This duobinary signal is branched into two, and becomes an inverted signal and a non-inverted signal by an inverting circuit 80 inserted in one of the paths.
The voltage is applied to the electrodes 84-1 and 84-2 of the MZ-type light intensity modulator 83 via the amplitude adjusting circuits 81-1 and 81-2 and the bias adjusting circuit 82, respectively. Electrodes 84-1, 8
Termination circuits 85-1 and 85-2 are connected to the other end of 4-2.

[0004] The output light of the semiconductor laser (LD) 86 is intensity-modulated in accordance with the two duobinary signals whose phases are inverted with each other, and the modulated signal light is transmitted to the optical fiber transmission line 87. At this time, 3 of the duobinary signal
As shown in FIG. 12, the two signal points are modulated in correspondence with the adjacent maximum transmittance point A, minimum transmittance point B, and maximum transmittance point C of the MZ type light intensity modulator, thereby forming a duobinary signal. Generate light. At points A and C, the intensity of the modulated signal light is maximum, but the phases are inverted.

[0005] The modulated signal light output from the optical fiber transmission line 87 is directly detected by an optical detection circuit 88, the detected signal is identified by a discriminator 89, and a logical data is inverted by an inverting circuit 90, whereby a binary data signal is obtained. Demodulated. The duobinary code is a kind of band compression code, and its occupied band is compressed to about half of a normal binary signal. Therefore, the duobinary signal light is more resistant to the chromatic dispersion of the optical fiber than the binary intensity modulated signal light (S. Kuwano et al.,
Electron. Lett., Vol. 31, pp. 1359-1361, 1995). In addition, since the carrier frequency component of the duobinary signal light obtained by the modulation is suppressed, stimulated Brillouin scattering (hereinafter, referred to as “SBS”) in the optical fiber.
And more power can be injected into the optical fiber (Yonega et al., IEICE Communications Society Conference 1995, B-773, 1995).

As a means for reducing signal degradation due to chromatic dispersion, there is a prechirp technique (N. Henmi et al.,
IEEE J. Lightwave Technol., Vol.12, pp.1706-1719,
1994). In this technique, frequency modulation is performed on modulated signal light in accordance with the light intensity, and pulse compression is caused by chromatic dispersion. This prechirp can be realized by directly changing the frequency of the light source in the case of direct modulation, and can be realized by using an MZ type light intensity modulator driven by two electrodes in the case of external modulation.

FIG. 13 shows a configuration example of a conventional optical pre-chirp transmission system using an MZ type optical intensity modulator. In the figure, a binary data signal to be transmitted is branched into two, and becomes an inverted signal and a non-inverted signal by an inverting circuit 80 inserted into one of the paths. The voltage is applied to the electrodes 84-1 and 84-2 of the MZ-type light intensity modulator 83 via the respective elements 82. A terminal circuit 85- is connected to the other ends of the electrodes 84-1 and 84-2.
1, 85-2 are connected. Amplitude adjusting circuits 81-1 and 8
1-2 sets chirp by setting the amplitudes of _two modulator drive signals V ₁ (t) and V ₂ (t) for driving the MZ light intensity modulator 83 to be different. The output light of the semiconductor laser (LD) 86 is subjected to light intensity modulation in accordance with the two modulator drive signals, and the modulated signal light is transmitted to the optical fiber transmission line 87. The modulated signal light output from the optical fiber transmission line 87 is directly detected by an optical detection circuit 88, and a binary data signal is demodulated by identifying the detected signal by an identifier 89.

FIG. 14 shows the amplitude and phase of a modulator drive signal and a modulated signal light in a conventional optical pre-chirp transmission system. The chirp parameter α representing the degree of chirp is

[0009]

(Equation 1) It is represented by Here, φ indicates the optical phase, and I indicates the light intensity.

Since this value generally depends on the light intensity I,
Α when the light intensity I is half of the peak is defined as a chirp parameter. For example, as an optical fiber transmission line
When transmitting an optical signal in the 1.55 μm band using a 1.3 μm zero-dispersion fiber, the signal given a negative chirp (α <0) is slower at the leading end of the pulse and faster at the tail end due to chromatic dispersion. As it travels through, pulse compression occurs. In the prechirp technique, the transmission limit limited by chromatic dispersion can be expanded by the pulse compression effect.

FIG. 15 shows a transmission characteristic of a conventional optical transmission system based only on chromatic dispersion. Here, the relationship between the transmission distance and the eye opening deterioration in the IM-DD system, the IM-DD system using prechirp, and the optical duobinary system is shown. The bit rate is 10 Gb / s and the dispersion value is 17 ps / km / nm. In the IM-DD system, the modulation band was set to 6 GHz, and the prechirp was set to a chirp parameter α of -0.8. The duobinary signal is generated by an ideal duobinary filter.

As shown in the figure, I using a pre-chirp
Although the M-DD system and the optical duobinary system have improved transmission characteristics, the optical duobinary system is advantageous for long-distance transmission of 100 km or more. further,
In long-distance repeaterless transmission, a large power must be incident on the optical fiber, so that an optical duobinary system in which SBS is less likely to occur is considered to be advantageous. In fact, duobinary signal light can be transmitted over 200 km over a 1.3 μm zero-dispersion fiber without repeaters, and a repeaterless transmission experiment at 210 km at 10 Gb / s has been reported (AJPrice et al., IEEE
hoton.Technol.Lett., vol.7, pp.1219-1221, 1995).

[0013]

In order to perform long-distance repeaterless transmission, a large signal power must be incident on an optical fiber. However, unless special measures are taken, the binary intensity modulated signal light has a fiber input power limitation by SBS, and the upper limit is about +10 dBm. In the optical duobinary system, a large signal power can be incident on an optical fiber, but the transmission distance is limited by signal deterioration due to a self-phase modulation (hereinafter referred to as “SPM”) effect due to a nonlinear refractive index of the optical fiber. You.

FIG. 16 shows transmission characteristics of a conventional optical duobinary transmission system. When 10 Gb / s duobinary signal light is transmitted, the deterioration at +14 dBm is larger than that at 0 dBm when the fiber input power is SP.
This is because the signal spectrum was broadened by M. Even if duobinary signal light is used, if a large signal power is incident on the optical fiber, the transmission distance is limited by the SPM. The same can be said for an optical repeater system in which an optical fiber amplifier or a semiconductor optical amplifier is inserted into an optical transmission line between a transmitting device and a receiving device.

An object of the present invention is to provide an optical transmitter capable of transmitting modulated signal light with little deterioration even when a large signal power is incident on an optical fiber. It is another object of the present invention to provide an optical transmission system capable of increasing the transmission distance and increasing the transmission speed by using the optical transmission device of the present invention.

[0016]

An optical transmitting apparatus according to the present invention comprises:
The binary data signal is converted into a duobinary signal, the intensity of the modulated signal light with respect to the median of the amplitude of the duobinary signal is the minimum, the intensity of the modulated signal light with respect to the other two values of the duobinary signal is the maximum, and Optical modulation means is used in which the phases of the modulated signal light are inverted with each other and the phase of the modulated signal light is continuously changed according to the intensity .

The light modulation means includes a code conversion unit, a modulator drive signal generation unit, a Mach-Zehnder interferometer type optical intensity modulator is configured using an optical phase modulating means, optical phase modulation hands
Stage is configured to shift the center value of the amplitude of a pair of modulator drive signal applied to the Mach-Zehnder interferometer type optical intensity modulator (duobinary signal) (claims 1, 2,
3) .

As described above, the chromatic dispersion and the strong duobinary signal light with respect to the SBS are given a phase change (chirp) depending on the intensity, so that the SPM which becomes a limiting factor when a large power enters the optical fiber. Can be reduced.

The optical transmission system of the present invention is configured by using an optical transmission device that chirps such a duobinary signal light. By setting the wavelength value of the optical carrier larger than the zero dispersion wavelength value of the optical fiber transmission line,
The effect of pre-chirp can be enhanced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS ( Reference Example of Optical Transmitting Apparatus) FIG. 1 shows a reference example of an optical transmitting apparatus according to the present invention . In the figure, a semiconductor laser (LD) 86 as a light source, a duobinary encoding circuit 70 as a code conversion means, an inverting circuit 80 as a light intensity modulation means, an amplitude adjustment circuit 81, a bias adjustment circuit 82, an MZ type light intensity modulation The device 83 (electrode 84, termination circuit 85) is the same as the transmitter of the conventional optical duobinary transmission system shown in FIG.

The feature of this embodiment is that the MZ type light intensity modulator 8
Modulated signal light (Duo binary signal light) output from 3
Is provided with a chirp imparting section 10 on the output side of the MZ-type light intensity modulator 83 as an optical phase modulation means for changing the phase of the MZ-type light intensity modulator 83 according to its intensity. The chirp imparting unit 10 includes:
An optical phase modulator 11, a delay adjustment circuit 12 for inputting a binary data signal and providing a predetermined delay, and an amplitude adjustment circuit 13 for adjusting the amplitude and driving the optical phase modulator 11, The phase of the duobinary signal light is modulated in proportion to the value data signal. The optical phase modulator 11 has:
A modulator utilizing the electro-optic effect of LiNbO ₃ or the like, a semiconductor laser amplifier, an electro-absorption optical modulator, or the like can be used.

FIG. 2 shows a configuration example of the duobinary encoding circuit 70. (a) Duobinary encoding circuit 70
Is a one-bit delay (T) 71 and an exclusive-OR circuit (EXOR) 72 for differentially encoding a binary data signal.
And a 1-bit delay (T) 73 and an adder 74 for generating a ternary duobinary signal from the intermediate sequence.

The duobinary encoding circuit 70 shown in FIG.
The configuration is such that a low-pass filter 75 is provided at the output stage of the adder 74 in FIG. (c) Duo binary encoding circuit 70
Is composed of a 1-bit delay (T) 71, an exclusive-OR circuit (EXOR) 72, and a low-pass filter 76 for duobinary signal generation. The transfer function of this filter is given by H (fT) = cos (πfT) | fT | ≦ 1/2 H (fT) = 0 | fT |> 1/2 Here, f is a frequency, T is a one-bit time width, and fT represents a frequency normalized by a bit rate. FIG. 3 shows the transmittance characteristics. In practice, this characteristic is approximately realized.

The duobinary signal light has two intensity levels, "ON" and "OFF". Therefore, when incident on an optical fiber with a large signal power, a general 2
Similarly to the value-intensity-modulated signal light, the signal spectrum is excessively broadened by the SPM generated by the nonlinear refractive index of the optical fiber. This spectrum spread increases the signal degradation due to chromatic dispersion and becomes a factor limiting the transmission distance. Therefore, in order to reduce the influence of SPM, the phase of the duobinary signal light is modulated in accordance with the light intensity to give chirp. The chirp providing unit 10 drives the optical phase modulator 11 using the binary data signal before duobinary encoding, and applies phase modulation to the duobinary signal light. Since “ON” and “OFF” of the duobinary signal light correspond to “space” and “mark” of the binary data signal before conversion, respectively, phase modulation according to the intensity of the duobinary signal light can be performed. it can. The duo-binary signal light having a chirp generated in this manner (hereinafter referred to as “chirped duo-binary signal light”) is transmitted to the optical fiber transmission line.

FIG. 4 shows a chirp providing section 1 in the reference example .
0 shows another configuration example . In this configuration, a part of the duobinary signal light is branched by the optical coupler 14, and the light intensity is detected by directly detecting the duobinary signal light by the optical detection circuit 15. The optical phase modulator 11 modulates the phase of the duobinary signal light passing through the optical coupler 14 according to the intensity of the duobinary signal light input via the delay adjusting circuit 12 and the amplitude adjusting circuit 13 and outputs the modulated signal. .

In the reference example described above, the duobinary signal light output from the MZ-type light intensity modulator 83 is input to the chirp applying section 10 and phase-modulated.
A configuration may be adopted in which the chirp imparting unit 10 is provided in a stage preceding the MZ light intensity modulator 83, and the carrier is phase-modulated and input to the MZ light intensity modulator 83. Even with such a configuration, it is possible to generate a chirped duobinary signal light in which the phase of the duobinary signal light is changed according to its intensity.

FIG. 5 (embodiment of the optical transmitter) shows an embodiment of the optical transmitter of the present invention (claim
1,2) . In the figure, a semiconductor laser 86 serving as a light source,
A duobinary encoding circuit 70 serving as a code converting means, an inverting circuit 80 serving as a light intensity modulating means, an amplitude adjusting circuit 81,
The bias adjustment circuit 82 and the MZ type light intensity modulator 83 (electrode 84, termination circuit 85) are the same as in the reference example shown in FIG.

The feature of this embodiment is that an optical phase modulation means for changing the phase of the modulated signal light output from the MZ type optical intensity modulator 83 according to its intensity and generating a chirped duo-binary signal light is as follows: M according to the binary data signal
There is provided a means for adjusting the amplitude of the modulator drive signal of the Z-type light intensity modulator 83. The means includes an amplitude adjustment circuit 21 for increasing the amplitude of the binary data signal by α ₀ , an adder 22 for adding the duobinary signal output from the duobinary encoding circuit 70 and the output of the amplitude adjustment circuit 21,
Adder 23 that adds the sign-reversed duobinary signal output from inverting circuit 80 and the output of amplitude adjusting circuit 21
And modulates the phase of the duobinary signal light in proportion to the binary data signal.

[0029] Figure 6 shows the generation process of the modulator drive signal in the embodiment. Electrode 84 of MZ type light intensity modulator 83
Modulator drive signal 1 to be applied to -1 (V ₁ (t)) includes a duobinary signal (d (t)), the amplitude is alpha ₀ times are binary data signal (α ₀ s (t)) and It is obtained by adding.
The modulator drive signal 2 (V ₂ (t)) applied to the electrode 84-2 of the MZ type light intensity modulator 83 has a sign-inverted duobinary signal ( d (t) ) and an amplitude α ₀ times. It is obtained by adding the binary data signal (α ₀ s (t)). α
₀ takes one of positive and negative values, the sign determines the direction of the chirp, and the absolute value determines the size of the chirp. In FIG. 5, it is possible to replace them with an inverting circuit 80 the adder 23 to one subtractor (claim
3 ).

The modulator drive signals 1 and 2 are vertically asymmetrical ternary signals in order to apply chirp simultaneously with optical duobinary modulation. The bias voltage is applied so that the intensity of the modulated signal light becomes minimum when both signals have a median value (not an intermediate value between the maximum value and the minimum value, but α ₀ V / 2 shown in FIG. 6). Figure 7 illustrates the amplitude and phase of <br/> Ru modulator drive signal put to the embodiment and the modulation signal light. The modulation is performed such that the intensity of the modulated signal light with respect to the central value of the ternary modulator drive signal is the minimum, the intensity of the modulated signal light with respect to the other two values is the maximum, and the phases are inverted. Here, the amplitude of the modulated signal light is obtained by inverting the phase and expressed by positive and negative signs. That is, the positive amplitude and the negative amplitude are phases inverted from each other, and it is understood that the optical duobinary modulation is correctly performed. It can be seen that the phase of the modulated signal light changes continuously according to the intensity of the modulated signal light.

( Reference Example of Optical Transmitting Apparatus) FIG. 8 shows a reference example of the optical transmitting apparatus of the present invention . In the figure, a semiconductor laser 86 serving as a light source, an inverting circuit 80 serving as light intensity modulation means, and two modulator drive signals V ₁ (t) and V ₂ (t).
Amplitude adjustment circuits 81-1 and
81-2, bias circuit 82, MZ type light intensity modulator 83
(Electrode 84, termination circuit 85) is the same as the transmission unit of the conventional optical pre-chirp transmission system shown in FIG. Chirp is given to the modulated signal light by the difference between the amplitudes of the two modulator drive signals, and the magnitude of the chirp can be changed according to the difference between the amplitudes (AHGnauck et a
l., IEEE Photon.Technol.Lett., vol.3, pp.916-918,
1991).

The feature of this embodiment is that the MZ type light intensity modulator 8
3 is provided with an optical phase modulator 11 for giving a phase change necessary for optical duobinary modulation to the modulated signal light output from 3. The optical phase modulator 11 is driven by the duobinary signal generated from the binary data signal by the duobinary encoding circuit 70, and the “on” optical phase of the modulated signal light corresponding to the maximum and minimum of the duobinary signal is changed. Phase modulation is performed so as to invert each other. The delay adjustment circuit 12 and the amplitude adjustment circuit 13 drive the optical phase modulator 11 by adjusting the delay amount and the amplitude of the duobinary signal. With this configuration, a similar chirped duo-binary signal light can be generated.

In the reference example described above, the modulation signal light output from the MZ type light intensity modulator 83 is input to the optical phase modulator 11 and converted into a chirped duobinary signal light. The optical phase modulator 11 may be provided before the optical modulator 83, and the carrier may be phase-modulated and input to the MZ optical modulator 83. Even with such a configuration, it is possible to generate a chirped duobinary signal light in which the phase of the duobinary signal light is changed according to its intensity.

FIG. 9 (embodiment of the optical transmission system) shows an embodiment of an optical transmission system of the present invention (請
Claim 5 ). In the figure, an optical transmitter 31 generates a chirped duobinary signal light using an optical transmitter as shown in FIG .
The optical receiving device 33 directly detects the chirped duobinary signal light by the optical detection circuit 88, identifies the detected signal by the discriminator 89, and logically inverts the detected signal by the inversion circuit 90 to demodulate the binary data signal.

[0035]

FIG. 10 shows the transmission characteristics of the optical transmission system of the present invention and the conventional optical duobinary transmission system. Chirp parameter α of chirped duo binary signal light
Was set to +1.4. The bit rate is 10 Gb / s, the fiber incident power is +14 dBm, and the fiber loss is 0.2 dB / km. In long-distance transmissions exceeding 150 km, chirped duo-binary signal light is superior, and it is possible to extend the transmission distance by about 50 km compared to conventional duo-binary signal light within an allowable range of 3 dB of eye opening degradation. it can.

[0036]

As described above, the optical transmission apparatus of the present invention and the optical transmission system using the same have a chirped transmission system.
By generating the duobinary signal light, deterioration due to SPM is reduced. Therefore, in an optical transmission system using an optical fiber having a relatively large dispersion value such as a 1.3 zero-dispersion fiber as a transmission line, it is possible to increase the transmission distance and increase the transmission speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a reference example of an optical transmission device according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a duobinary encoding circuit 70.

FIG. 3 is a low-pass filter 7 for generating a duobinary signal.
FIG. 6 is a diagram showing transmittance characteristics of No. 6;

FIG. 4 is a block diagram showing another configuration example of the chirp imparting unit 10 in the reference example .

FIG. 5 is a block diagram showing an embodiment of the optical transmission device of the present invention.

FIG. 6 is an exemplary view for explaining a process of generating a modulator drive signal in the embodiment.

7 is a diagram showing the amplitude and phase of the modulator drive signal and the modulation signal light in the embodiment.

FIG. 8 is a block diagram showing a reference example of the optical transmission device of the present invention.

FIG. 9 is a block diagram illustrating a configuration example of an optical transmission system according to the present invention.

FIG. 10 is a diagram showing transmission characteristics of the optical transmission system of the present invention and a conventional optical duobinary transmission system.

FIG. 11 is a diagram showing a configuration example of a conventional optical duobinary transmission system.

FIG. 12 is a diagram for explaining the operation of an MZ type optical intensity modulator in a conventional optical duobinary transmission system.

FIG. 13 is a diagram showing a configuration example of a conventional optical pre-chirp transmission system using an MZ type optical intensity modulator.

FIG. 14 is a diagram showing an amplitude and a phase of a modulator drive signal and a modulated signal light in a conventional optical prechirp transmission system.

FIG. 15 is a diagram showing transmission characteristics of a conventional optical transmission system based only on chromatic dispersion.

FIG. 16 is a diagram showing transmission characteristics of a conventional optical duobinary transmission system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Chirp provision part 11 Optical phase modulator 12 Delay adjustment circuit 13, 21 Amplitude adjustment circuit 14 Optical coupler 15 Optical detection circuit 16, 75 Low-pass filter (LPF) 22, 23 Adder 31 Optical transmitter 32, 87 Optical fiber Transmission path 33 Optical receiving device 70 Duo-binary encoding circuit 71, 73 1-bit delay (T) 72 Exclusive OR circuit (EXOR) 74 Adder 76 Low-pass filter for duo-binary signal generation 80 Inverting circuit 81 Amplitude adjustment Circuit 82 Bias adjustment circuit 83 MZ type light intensity modulator 84 Electrode 85 Termination circuit 86 Semiconductor laser (LD) 88 Optical detection circuit 89 Discriminator 90 Inverting circuit

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H04B 10/142 10/152 10/26 10/28 (56) References JP-A-7-58698 (JP, A) JP-A 2-269309 (JP, A) Yonnega, S.M. Kuwano, S.M. Norimatsu, N .; Shibuta, Optical duo binary transmission system with no receiver sensitivity degradation, Electronics Letters, February 16, 1995, vol. 31 No. 4, 302-304 (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/00-1/125 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. An optical transmission system comprising: a light source that outputs an optical carrier; and an optical modulator that receives a binary data signal and outputs a modulated signal light obtained by modulating the optical carrier according to the binary data signal. In the apparatus, the light modulating means converts a binary data signal into a duobinary signal.
Conversion means, and the phase is inverted from the duo-binary signal with the same amplitude.
Drive signal generation for generating a pair of modulator drive signals
Means for inputting said pair of modulator drive signals and split into two
The optical intensity is modulated by changing the phase of the optical carrier.
Single Mach-Zehnder interferometer-type optical power that outputs modulated signal light
Degree modulator, shift only the median of the pair of modulator drive signals,
The intensity of the modulated signal light becomes minimum with respect to the median value.
Therefore, the intensity of the modulated signal light becomes maximum with respect to the other two values.
Optical phase shifter for setting the pair of modulator drive signals so that
Optical transmitter is characterized in that a regulating means. 2. An optical phase modulator, comprising: a means for receiving a binary data signal and adjusting the amplitude thereof; and a means for adding the amplitude-adjusted binary data signal to a pair of modulator drive signals. The optical transmission device according to claim 1 , further comprising: 3. A modulation modulator drive signal generation means and an optical phase modulation means, comprising: a means for inputting a binary data signal and adjusting the amplitude thereof; a duobinary signal output from a code conversion means; to add and subtract the binary data signal adjusted to the claim 1, characterized in that the amplitude is equal phase is inverted and median and means for generating a pair of modulator drive signals shifted The optical transmission device as described in the above. Wavelength value of 4. The optical carrier is an optical transmission device according to any one of claims 1 to 3, wherein the greater than the zero dispersion wavelength value of the optical fiber-modulated optical signal is transmitted. 5. The optical transmission device according to claim 1 , wherein the optical transmission device receives the modulated signal light output from the optical transmission device and demodulates the modulated signal light; and the optical transmission device and the optical reception device. An optical transmission system, comprising: an optical transmission line that couples with an apparatus. 6. The optical transmission system according to claim 5 , wherein the optical receiving device is configured to perform direct optical detection.