WO2001037460A1

WO2001037460A1 - Optical communication method and optical component used in the method, and optical communication device comprising the component

Info

Publication number: WO2001037460A1
Application number: PCT/JP2000/008023
Authority: WO
Inventors: Kazuro Kikuchi; Yuichi Takushima; Mark Kenneth Jablonski; Yuichi Tanaka; Haruki Kataoka; Noboru Higashi; Kenji Furuki; Shiro Yamashita
Original assignee: Oyokoden Lab Co., Ltd.
Priority date: 1999-11-16
Filing date: 2000-11-14
Publication date: 2001-05-25

Abstract

In the field of optical communication using an optical fiber for communication transmission line, it has been conventionally difficult to use an optical fiber practically put in use for high-speed long-distance communication at, e.g. 40 Gbps mainly because of dispersion in an optical signal transmitted through the optical fiber, and the security has been not effective. An optical communication method for transmitting an optical signal through an optical fiber after imparting dispersion to the signal using an optical dispersion imparting element comprising a multilayer film or a compensating element and compensating for the imparted dispersion or the dispersion produced in transmission so as to allow the signal to be received accurately even in high-speed long-distance optical communication, an optical component, and an optical communication device comprising the component are disclosed. Especially, the third-order dispersion is significantly effectively suppressed and compensated for. Before an optical signal is inputted to a transmission line, the signal is subjected to dispersion appropriately to enhance its security.

Description

Description: Optical communication method, optical component used in the method, and optical communication device using the component

The present invention reduces second-order or higher chromatic dispersion (hereinafter, also simply referred to as dispersion) that occurs in optical communication using an optical fiber (hereinafter, simply referred to as fiber) in a transmission path. The present invention relates to an optical communication method, an optical component and an optical communication device that can be used in the method.

Here, the optical component is a component that can be used for optical communication, and is at least an element capable of compensating for a second-order or higher dispersion, in particular, a third-order dispersion (hereinafter referred to as a second-order or An element capable of compensating for the second- or higher-order dispersion is also called an element capable of changing the second-order dispersion, or a second-order optical dispersion compensating element. Similarly, an element capable of compensating for third-order or higher-order dispersion can also be used as an element capable of changing third-order dispersion or a third-order dispersion compensating element. ) Or a component having an element capable of performing dispersion (hereinafter, also referred to as a dispersion compensation element), and includes the case of a single dispersion compensation element or a single dispersion generation element.

Further, the optical communication device is a device that can be used for optical communication, wherein dispersion compensation and dispersion generation are performed using the optical component.

The optical communication method is a method of performing accurate communication by performing dispersion using the optical component or the optical communication device or compensating for dispersion generated in signal light or the like.

Hereinafter, the term “chirp” used in the present invention is mainly used to mean “group velocity delay” or “wavelength dispersion”.

The dispersion compensating element of the present invention may be only the second or third-order dispersion compensating element described above, or may include a unit for changing an incident position of incident light in an incident plane, and the like. In some cases, not only third-order or higher-order dispersion compensation but also second-order dispersion compensation is possible, and it may be implemented in a case. There is a case where the device is not mounted on a chip, that is, a so-called chip shape or wafer shape. The same applies to the dispersion generating element.

The dispersion compensating element and the dispersion generating element of the present invention include all of these forms, and can take various forms according to the usage status, the purpose of sale, and the like. In the present invention, the second-order dispersion compensation means "compensating the slope of the wavelength-time characteristic curve described later with reference to FIG. 9 (A)", and the third-order dispersion compensation is " A) to compensate for the bending of the wavelength-time characteristic curve described later. " Background art

In optical communication using optical fiber, long-distance transmission is performed like a communication transmission line typified by a submarine cable. A rate of 2.5 Gbps (2.5 gigabits per second) is not sufficient, and signals with bit rates as high as 40 Gbps, 80 Gbps, and 160 Gbps The use of light has been attempted.

In such an environment, since the refractive index and speed vary depending on the spectrum component and the rate of change of the intensity of the signal light, it is known that the pulse spreads and changes such as distortion, cracking and sub-pulses occur. Have been.

As the pulse width of the signal light input to the transmission path decreases and the rate of change of the pulse intensity increases, nonlinear phenomena become more pronounced, and the change of the signal light pulse increases. In high-speed and long-distance communication, changes in optical pulses due to linear phenomena and nonlinear phenomena hinder communication, and are major issues to be solved. That is, in the case of high-speed communication in which the pulse width of the signal light is reduced and the rate of change of the pulse intensity is increased, the change in the waveform of the signal light becomes large and normal communication cannot be performed.

Fig. 11 is a diagram for explaining changes in signal light when long-distance transmission is performed by a conventional communication method. The communication bit rate is (A) is 2.5 Gbps, and (B) is 10A and 10B are diagrams illustrating optical communication at 10 Gbps and FIG. 10C illustrates optical communication at 40 Gbps.

In FIG. 11, reference numerals 7a, 7b, and 7c denote spectrums of signal light having communication bit rates of 2.5 Gbps, 10 Gbps, and 40 Gbps, respectively. The intensity and the horizontal axis are wavelength. Symbols 71 a, 72 a, and 73 a are communication bit rate powers.Sending waveform when transmitting at 2.5 Gbps, 71 b, 72 b, and 73 b are communication bit rates. Is the transmission waveform when transmitting at 10 Gbps, 71 c, 72 c, and 73 c are the transmission waveforms when transmitting at a communication bit rate of 40 Gbps. al, 73 al, 71 b1, 72 bl, 73 bl, 71 cl, 72 cl, 73 cl are the transmission waveforms 71 a, 72 a, 73 a, 71 b, respectively , 72b, 73b, 71c, 72c, 73c f In each of the above communication bit rates, an optical fiber or an optical fiber transmission system (Also referred to as fiber) after being transmitted over long distances, the vertical axis is the light intensity, and the horizontal axis is the time. In each case, the waveform on the left side of the figure is the first. Sent or received.

In the case of communication bit rates of 2, 5 Gbps and 1 OG bps, the signal light emitted from the optical fiber enters the optical fiber as shown in Figs. 11 (A) and (B). The left and right sides are almost symmetric with respect to the almost symmetrical waveform of the previous signal light, and the pulse width is slightly widened.

In the case of a communication bit rate of 40 Gbps, as shown in Fig. 11 (C), the signal light emitted from the optical fiber has a substantially symmetrical waveform before entering the optical fiber. As a result, the right side of the figure is greatly deformed, and it is difficult to distinguish one signal light from the next.

In conventional 2.5 Gbps and 10 Gbps optical communications, the signal light input to the optical fiber (hereinafter also referred to as incident) has a gradual change in pulse intensity and a wide panoramic width. The effect of nonlinear phenomena is small and can be treated as almost linear phenomena. The intensity and wavelength of signal light incident on the optical fiber during long-distance transmission vary as shown in Figs. 11 (A) and (B), but two or more Even when transmitting light, the signal light does not change so much as to affect the discrimination of each signal light, and the signal light transmitted by the optical fiber can be accurately received.

However, in high-speed communication at 40 Gbps, the signal light entering the optical fiber has a narrow pulse width and a sudden change in pulse intensity, so it enters the optical fiber during long-distance transmission. The signal light intensity and wavelength greatly change as shown in Fig. 11 (C), and therefore the signal light incident on the optical fiber is almost completely changed. There was a big problem that it was not possible to receive accurately.

There is a strong demand for higher optical communication bit rates than currently used, and various studies have been conducted to realize high-speed communication at 40 Gbps, 80 Gbps, and 160 Gbps. Has been done.

Using conventional fiber optic communication systems, for example, to transmit 10,000 km at 40 Gbps, or to transmit a long distance such as 100 Okm at 80 Gbps, the tertiary It is said that the effect of dispersion of the optical fiber is so great that accurate communication cannot be performed, and as a solution to this, a proposal has been made to change the optical fiber itself.

The present invention has been made to solve such a conventional problem. However, in order to clarify the present invention, the following description will be made with reference to FIG. 9 and FIG. Will be described.

FIG. 10 is a diagram illustrating the dispersion-wavelength characteristics of a single mode optical fiber (hereinafter, also referred to as SMF), a dispersion compensation fiber, and a dispersion shift fiber (hereinafter, also referred to as DSF). In FIG. 10, reference numeral 8001 denotes a graph showing the dispersion-wavelength characteristics of the SMF, reference numeral 802 denotes a graph showing the dispersion-wavelength characteristics of the dispersion compensating fiber, and reference numeral 803 denotes a graph showing the dispersion-wavelength characteristics of the DSF. The vertical axis is dispersion and the horizontal axis is wavelength.

As can be seen from Fig. 10, in the SMF, the dispersion increases as the wavelength of the light input to the fiber increases from 1.3 / im to 1.8 μπι. The dispersion decreases as the wavelength increases from 1.3 μπι to 1.8 μηι. In the DSF, the dispersion decreases as the wavelength of the input light increases from 1.2 / im to around 1.55 / zm, and the wavelength of the input light increases from around 1.55 / zm to 1.8. The variance increases with increasing length to μπι. In optical communication at 2.5 Gbps (2.5 gigabits per second) using DSF when the wavelength of the input light is around 1.55 μπι, dispersion does not cause a problem in optical communication.

Fig. 9 is a diagram for explaining the dispersion compensation method. (A) shows the wavelength-time characteristic and the optical intensity-time characteristic of the signal light, and (B) shows the results using SMF and dispersion compensation fiber. (C) is a diagram for explaining an example of transmission on a transmission line configured only with SMF. In FIG. 9, reference numerals 70 1 and 71 1 denote graphs showing characteristics of signal light before being input to the transmission line, reference numeral 730 denotes a transmission line configured by SMF 731, and reference numeral 70 2 And 7 1 2 are graphs showing the signal light characteristics when the signal light having the characteristics shown in the graphs 7 0 1 and 7 1 1 is transmitted through the transmission line 7 30 and output from the transmission line 7 30 Where 720 is the transmission path composed of the dispersion compensating fiber 72 1 and SMF 72 2, and 70 3 and 71 3 are the signal light with the characteristics indicated by the graphs 70 1 and 71 1 Is a rough graph showing the characteristics of signal light in a state where the signal light is transmitted through the transmission path 720 and output from the transmission path 720. Reference numerals 704 and 714 indicate that the signal light having the characteristics shown in the graphs 701 and 711 is transmitted through the transmission path 720 and output from the transmission path 720, and then the receiver Is a graph showing characteristics of signal light when desirable third-order dispersion compensation described later is performed by the optical dispersion compensating element used in the present invention arranged in FIG. 7, which almost agrees with the graphs 70 1 and 71 1 . The graphs 7 0 1 7 0 2 7 0 3 7 4 are graphs with the vertical axis representing wavelength and the horizontal axis representing time (or time), respectively. The graph 7 1 1 7 1 2 7 1 3 7 1 4 is a graph in which the vertical axis represents light intensity and the horizontal axis represents time (or time). Reference numerals 72 4 and 7 34 denote transmitters, and reference numerals 7 25 and 7 35 denote receivers.

As described above, the conventional SMF increases the dispersion as the wavelength of the signal light increases from 1.3 μπι to 18 μιη, so that in high-speed communication and long-distance transmission, the group due to dispersion increases. This causes a speed delay. In the transmission path 730 constituted by the SMF, the signal light is significantly delayed on the long wavelength side compared to the short wavelength side during transmission, as shown in graphs 702 and 712. For example, in high-speed communication and long-distance transmission, the signal light that has changed in this way has a large degree of change, and may not be received as an accurate signal because it overlaps with the preceding and following signal lights.

Conventionally, in order to solve such a problem, dispersion is compensated (hereinafter, also referred to as correction) by using a dispersion compensating fiber as shown in FIG. The conventional dispersion compensating fiber, to solve the problems of the SMF of dispersion as minute wavelength 1. the longer of 3 _M m to 1. 8 mu m increases, the aforementioned good urchin, wavelength 1.3 The dispersion is designed to decrease as the length increases from / m to 1.8 μπι. The dispersion compensating fiber can be used, for example, by connecting a dispersion compensating fiber 721 to SΜF 722 as shown by a transmission line 720 in FIG. The transmission line At 720, the signal light is plotted between the SMF 722 and the dispersion compensating fiber 721, because the tendency of the delay on the short wavelength side and the long wavelength side is reversed. As shown in Fig. 3, the amount of change is smaller than the changes shown in graphs 702 and 712.

However, in the conventional method of compensating for the second-order chromatic dispersion using the dispersion compensating fiber, the chromatic dispersion of the signal light transmitted through the transmission line is represented by the state of the signal light before being input to the transmission line, that is, as shown in FIG. The dispersion cannot be compensated for up to the shape of 0 1, and the limit is to compensate for the shape of graph 70 3. As shown in graph 703, in the conventional so-called second-order chromatic dispersion compensation method using a dispersion compensation fiber, the light of the central wavelength of the signal light is converted into light of the short wavelength side and light of the long wavelength side. In comparison, only the light of the shorter wavelength side and the longer wavelength side of the light of the central wavelength component of the signal light is delayed. Then, as shown in the left end of the graph 7 13, a ripple may be generated in a part of the graph. If an attempt is made to reduce the occurrence of dispersion by using the above-described method, the cost of parts will increase, the single mode cannot be maintained due to the expansion of the core area, or light will be emitted from the bent fiber. In addition to problems such as increased light loss in the communication transmission line due to leakage, etc., depending on the communication conditions, the problem also arises when communication becomes impossible.

However, at present, no practical solution has been found, and as a countermeasure, second- or third-order dispersion compensation has been attempted, but a low-loss and effective method applicable to optical communication. It has also been predicted that, as described above, the fiber itself must be changed to accommodate this. As a result, the fiber and related components of optical communication accumulated up to now will require major changes, which may render conventional methods and equipment unusable, resulting in large social and economic losses. Is expected.

The present invention has been made in view of such a point, and an object of the present invention is to consider the optical communication wavelength band called L band, C band, S band, etc. A communication method that can solve the above-mentioned problems in high-speed and long-distance communication in the optical communication wavelength band including the wavelength band of 146 to 160 nm and other wavelengths. And providing optical components and optical communication devices Disclosure of the invention

In order to achieve the object of the present invention, a communication method according to the present invention comprises an optical fiber and an optical dispersion compensator at least as a communication transmission line (hereinafter referred to simply as an optical dispersion compensator). In the following, compensation for dispersion caused by transmission through a fiber or the like is performed, and as described later, dispersion of signal light transmitted in advance by applying dispersion to signal light is restored. That is, in the present invention, a device having one or both functions of restoring dispersion is collectively referred to as a dispersion compensator, and especially when it is necessary to distinguish or limit the dispersion compensator in a narrow sense. To compensate for the dispersion generated in the signal light during transmission of the signal light until it can be correctly received as the signal light. That you can Features.

Furthermore, examples of the optical communication method of the present invention include at least an optical fiber and an optical dispersion generator used for a communication transmission line (hereinafter, the optical dispersion generator is also simply referred to as a dispersion generator). )) And the dispersion compensator is used to transmit the signal light subjected to dispersion by the dispersion generator, transmit the optical fiber, and restore to the correct signal light by the dispersion compensator capable of applying inverse dispersion. It is characterized by the ability to

The example of the optical communication method of the present invention is characterized in that signal light is dispersed and then transmitted in a fiber, and such a method is used for security measures such as preventing eavesdropping. Not only can reduce the nonlinear phenomena caused by transmission through the fiber.

In order to achieve the object of the present invention, in the communication method, the optical component and the optical communication device of the present invention, at least one of a secondary dispersion compensating element and a tertiary dispersion compensating element is used as a dispersion compensating element. It is characterized by:

Further, the example of the present invention is characterized in that at least one of a secondary dispersion generating element and a tertiary or higher dispersion generating element is used as the dispersion generating element.

In order to further enhance the effect of the present invention, the dispersion compensating element used in the present invention is composed of, for example, a multilayer film such as a dielectric multilayer film. It is characterized in that the reflective layer is formed so as to form at least two cavities that cause a resonance phenomenon.

Further, in order to enhance the effect of the present invention, the dispersion compensating element used in the present invention is characterized by having at least two cavities having different resonance (resonance) wavelengths.

The example of the dispersion compensating element used in the present invention is characterized in that each of the reflective layers of the multilayer film has a different reflectance.

In order to enhance the effect of the present invention, the multilayer film, when considered as the optical path length of incident light, has a thickness (hereinafter, referred to as “thickness”) corresponding to a quarter of the central wavelength of the incident light. (Also referred to as a quarter wavelength) as a unit layer, and the reflectivity of each of the reflective layers is calculated as R 1 in order from the side where incident light is incident. , R 2, R 3, ·· ', the reflectance of each reflective layer is R 1 ≤ R 2 ≤ R 3 · ·' (where i = 1, 2, 3,, · · , The number of reflective layers is the upper limit).

Each layer of the multilayer film has a quarter wavelength and a relatively high reflectance (hereinafter, also referred to as a layer H), and a layer having a quarter wavelength and a relatively low reflectance. (Hereinafter, also referred to as a layer L). In order to enhance the effect of the present invention, the third-order dispersion compensating element used in the present invention includes, in order from the side where the incident light is incident, at least a first having a reflectivity of 84 to 88%. Reflective layer, first light-transmitting layer, second reflective layer with reflectivity of 99.5 to 99.8%, third light-transmissive layer, third with reflectivity of 99.9% or more It is characterized by having a reflective layer.

The relatively high reflectivity and the relatively low reflectivity mean that the reflectivity is relatively high or relatively low between the unit layers forming the reflective layers constituting the multilayer film. Means

An example of the third-order dispersion compensating element used in the present invention includes, in order from the side where the incident light is incident, three sets of the combined layers of the layers H and L, and 10 sets of the combined layers of the layers H and H. Set, one set of layer L, 9 sets of combined layers of layer H and layer L, 7 sets of combined layers of layer H and layer H, one set of layer L, and one set of layer H and layer L 1 3 sets It is characterized by having a formed multilayer film.

Their to, for occupying become large the effect of the present invention, the dispersion compensation element used in the present invention, as the main, T i O ₂ (titanium dioxide), T a ₂ 0 ₅ (tantalum pentoxide), N b ₂ 0 that has a layer and S i 〇 ₂ multilayer film is composed of a laminated film of a combination of one or both of layer mainly containing (silicon dioxide) containing either (niobium pentoxide) It is a feature.

In order to enhance the effect of the present invention, a preferable example of the dispersion compensating element used in the present invention is that the layer H is mainly composed of any one of TiO ₂ , TaO, and ΝbΟ. It is characterized in that the layer L is mainly formed of a layer composed of SiO ₂ .

In order to enhance the effect of the present invention, an example of the dispersion generating element used in the present invention is an element in which the dispersion generating element has a multilayer film, and the multilayer film has at least two reflections. It is characterized by having layers.

In order to enhance the effects of the present invention, examples of the dispersion generating element used in the present invention include at least three reflective layers, and each of the reflective layers has a refractive index at a quarter wavelength. A layer having a relatively high refractive index (hereinafter, also referred to as layer H) and a layer having a quarter wavelength and a relatively low refractive index (hereinafter, also referred to as layer L). It is characterized by

In the communication method of the present invention, the dispersion compensator and the dispersion generator as described above can be arranged at any necessary place in a communication system using an optical fiber. For example, the optical component or optical communication device of the present invention is appropriately arranged as necessary in a receiver, a transmitter, a wavelength multiplexer, a wavelength demultiplexer, an amplifier or other various repeaters, or an optical fiber transmission line. can do. Such an optical component or optical communication device has a small number of dispersion compensators (also referred to as dispersion restoration units and chip restoration units, depending on the contents) and dispersion generators (also referred to as chirp generators). Both are arranged.

The dispersion compensator included in the optical communication device of the present invention has the dispersion compensation element as described above, and the dispersion generator has the dispersion generation element as described above. ing. An example of the dispersion generating element used in the present invention is such that each of the reflective layers has a thickness of one quarter wavelength and a relatively high refractive index (hereinafter also referred to as a layer H) and a thickness of four quarters. It is characterized by being composed of a plurality of combinations of layers each having a relatively low refractive index at one wavelength (hereinafter, also referred to as layer L).

An example of the optical communication apparatus according to the present invention is characterized in that it has at least one of a plurality of dispersion compensating elements and a plurality of dispersion generating elements.

An example of the optical communication apparatus according to the present invention includes means for displaying information on dispersion such as dispersion to be applied to the signal light and types of dispersion or values of dispersion applied or generated to the signal light, and performing dispersion or compensation. Or at least one of means for inputting the shared information for performing the operation.

An example of the optical communication apparatus according to the present invention is such that when the communication bit rate of the input light to the optical fiber is 40 Gbps or more, the dispersion applied to the input light is the optical fiber or the optical fiber. When the dispersion received during the transmission of the transmission system has the same peak value of the input light without dispersion and the communication bit rate is 2.5 Gbps, the dispersion is applied to the input light. The characteristic is that the distortion is not greater than the dispersion-based deformation experienced when the same optical fiber or optical fiber transmission system is transmitted the same distance without using the same distance.

According to the present invention, the signal light dispersed by the dispersion generator can be used for high-speed communication with a communication bit rate of 40 Gbps or more and communication over a long-distance transmission path having a large peak. However, the occurrence of dispersion can be suppressed to the extent that accurate communication is possible, and the signal light output from the transmission line can be converted to the original signal light by the dispersion restoration device. When the received signal light is restored by the dispersion restoration unit, for example, information from the dispersion measurement unit is used, or transmission is performed in advance in consideration of the dispersion occurrence state of the transmission system. The signal light can be restored by compensating for the dispersion including the dispersion generated during the signal transmission. Also, the signal light transmitted after being appropriately dispersed by the dispersion generator is observed as a flow of CW noise (continuous wave noise) even if it is extracted by any means in any optical fiber of the transmission line. Therefore, it is not possible to count the pulses, and it is not possible to implement with high reliability the prevention of eavesdropping that could not be realized in optical communication until now, which was regarded as a problem. Any security problem can be solved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating, using a model, a dielectric multilayer filter used in a third-order dispersion compensator according to the present invention.

FIG. 2 is a diagram illustrating reflected light from the filter in FIG.

FIG. 3 is a diagram illustrating a dielectric multilayer filter used in an example of the present invention. FIG. 4 is a graph illustrating measured values of light reflected by the dielectric multilayer film filter of the present invention.

FIG. 5 is a diagram illustrating an embodiment of a cap control of the present invention.

FIG. 6 is a diagram illustrating signal light during long-distance transmission in an optical fiber to which the present invention is applied.

FIG. 7 is a diagram illustrating an example in which the present invention is applied to an optical communication system.

FIG. 8 is a diagram illustrating wavelength-multiplexed signal light.

FIG. 9 is a diagram for explaining the chromatic dispersion compensation method. (A) shows the wavelength-time characteristic and the light intensity-time characteristic, (B) shows the second-order chromatic dispersion compensation by the dispersion compensation fiber, and (C) () Is a diagram illustrating a single-mode optical fiber transmission line.

FIG. 10 is a diagram showing dispersion-wavelength characteristics of various fibers.

Fig. 11 is a diagram for explaining changes in signal light intensity and wavelength when long-distance transmission is performed by a conventional communication method. The communication bit rate (A) is 2.5 Gbps. (B) is a graph at 10 Gbps, and (C) is a graph at 40 Gbps. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings used in the description schematically show the dimensions, shapes, arrangement relations, and the like of the components so that these inventions can be understood. Also, in each of the drawings, similar constituent components may be denoted by the same reference numerals, and redundant description may be omitted.

FIG. 1 shows a dielectric multilayer filter used in the third-order dispersion compensating element of the optical component of the present invention. FIG. 3 is a diagram illustrating a model using a model. In FIG. 1, reference numeral 100 represents a dielectric multilayer filter, 101 represents incident light, 102 represents reflected light, 103, 104, and 105 represent reflectances of less than 100%. Reflective layer (hereinafter also referred to as reflective film), 106 is a reflective layer with a reflectance of about 100%, 108, 109, 110 is a light-transmitting layer, 111, 11 2, 1 1 and 3 are cavities. Reference numeral 107 denotes a substrate, for example, using BK-7 glass (trade name of Shott, Germany).

The reflectance of each reflective layer 103, 104, 105, 106 in FIG. 1 is represented by R (103), R (104), R (105), R (104). 6), each reflectance has a relation of R (103) ≤ R (104) ≤ R (105) ≤ R (106). That is, the multilayer film is formed such that the reflectance of each reflection layer increases in the thickness direction of the multilayer film from the reflection layer on the side where the incident light is incident. The formation positions of the respective reflective layers are selected so that the intervals when considered as the optical path lengths between the respective reflective layers are different from each other. By doing so, the design accuracy of the reflectance of each reflective layer can be relaxed, and a combination of unit films having a thickness of a quarter wavelength is used for the third-order dispersion compensating element of the present invention. A multilayer film can be formed, and a highly reliable and inexpensive tertiary dispersion compensating element can be provided at low cost.

FIG. 2 illustrates the reflected light 102 output from the multilayer film filter 100 shown in FIG. 1 after the incident light 101 incident on the dielectric multilayer filter 100 is appropriately reflected or transmitted by each reflection layer and subjected to dispersion compensation. The vertical axis is the group velocity delay time (unit: ps, picoseconds), and the horizontal axis is the difference between each wavelength and the central wavelength of the incident light.

In FIG. 2, the reference numeral 200 denotes a cavity 111, and the incident light 101 enters a dielectric multilayer filter in which the cavities 111, 112, and 113 are formed as the reference numeral 100 in FIG. FIG. 4 is a graph showing the group velocity delay of the reflected light 102, in which a cavity having the same effect as the cavity 111 is formed singly on the substrate, and the incident light 101 enters the substrate. In the same way, the light reflected by the substrate is formed by forming a cavity having the same effect as that of the cavity on the substrate, and the incident light is reflected by the incident light. , 203 are graphs showing the group velocity delays of the light formed by forming a cavity having the same effect as the cavity 113 on the substrate alone, making incident light 101 incident and reflected. . The reflected light resonated only by the cavities 111 has a short group velocity delay maximum and a gradual change in group velocity delay for each wavelength, as shown by the graph 201 in FIG. The reflected light resonated only by the cavities 1 and 2 has a maximum group velocity delay time longer than that of the graph 201 as shown by the graph 202 of FIG. The change is big. The reflected light resonated only by the cavities 113 has a longer group velocity delay time as shown by the graph 203 in FIG. 2, and the change in the group velocity delay time for each wavelength is even greater. If the wavelength width (wavelength band) that causes a change in the group velocity delay to a certain extent or more is called the bandwidth, the bandwidth becomes narrower in the order of graphs 201, 202, and 203. The incident light 101 incident on the dielectric multilayer filter 100 having the cavities 1 1 1, 1 1 2 and 1 1 3 having the above-described characteristics in the configuration as shown in FIG. 1 is converted into the cavities 1 1 1 Then, the cavities 1 1 and 2 resonate at the cavities 1 1 and 3 respectively, and are reflected. As a result, the reflected light 102 becomes as shown by the graph 200 in FIG. As shown in graph 200, in the case of the reflected light that is incident on and output from the dielectric multilayer filter 100, the delay time at the center wavelength of the graph is the largest, and the maximum delay time is 0 1 is longer and shorter than in graphs 202 and 203, but the bandwidth is narrower than in graph 201 and is lower than in graphs 202 and 203. In addition, the group velocity delay time-wavelength characteristic can be obtained. By appropriately selecting the maximum delay time and the bandwidth in accordance with the state of dispersion desired to be compensated in optical communication, compensation of third-order or higher dispersion (hereinafter also referred to as third-order dispersion compensation) is performed effectively. I can do it.

Then, by appropriately changing the configuration of the dielectric multilayer film, for example, by changing the film thickness, a dielectric multilayer filter that obtains a group velocity delay time-wavelength characteristic curve capable of compensating secondary dispersion is manufactured. You can also.

FIG. 3 is a diagram illustrating a dielectric multilayer filter used in an example of the present invention. In FIG. 3, reference numeral 300 denotes a dielectric multilayer film filter, 301 denotes BK-7 glass as a substrate, and 302 denotes a reflective layer (a reflective layer together with an intermediate layer 303 described later). 13 sets of a combined layer of layer H and layer L (hereafter, also referred to as HL film) with the reflective layer 302 and the intermediate layer 303 forming a third reflective layer. Multilayer film (hereinafter also referred to as HL multilayer film), 303 and 303 are films of layer L as an intermediate layer, 304 H is a second light transmitting layer, a multilayer film having 7 sets of a combined layer of layer H and layer H (hereinafter also referred to as HH film) (hereinafter also referred to as HH multilayer film), Is a reflective layer (which acts as a reflective layer together with the intermediate layer 306, and the reflective layer 305 and the intermediate layer 306 form a second reflective layer), and is composed of 9 sets of HL films. HL multilayer film, 307 is the first light transmission layer, has 10 sets of HH films, HH multilayer film, 308 is the first reflection layer, has 3 sets of HL films HL multilayer film, 311 is a first cavity (resonator) between the first reflective layer 310 and the second reflective layer, 312 is a second reflective layer and the second reflective layer The second cavity between the three reflective layers. The reflective layer is formed by stacking a plurality of layers having different refractive indices, in which light is scattered, interferes (multiplexes), and is reflected. Details of what it is are omitted here.

Film of the HL, the film thickness is created by Ion'ashisu preparative deposition of T i 〇 ₂ quarter wavelengths (hereinafter also referred to as Ion'ashisu preparative layer) and the layer H formed in a thickness of one quarter A layer L formed of an ion-assist film having a wavelength of S i 〇 ₂ , and one layer of the ion-assist film (layer H) having the T i 〇 _{2 and} an ion-assist film of S i O ₂ (layer). ) One set of HL film is composed of one combined layer. The HH film is a set of two combined layers of a layer H composed of an ion-assist film having a thickness of T i 0 _{2 having} a quarter wavelength. The films 303 and 306 of the layer L are each composed of one layer of an ion assist film of SiO _{2 having} a thickness of a quarter wavelength.

The reflectivity of the first, second, and third reflective layers is increased in the order of the first reflective layer, the second reflective layer, and the third reflective layer. The reflectance is about 100%, the reflectance of the second reflective layer is about 99.8%, and the reflectance of the HL multilayer film 308 as the first reflective layer is about 86%. In addition, it is preferable that each of the reflectances is within 3% of the above value, more preferably within 0.5% depending on required specifications. The reflectivity of the first reflective layer is set to 84 to 8.8%, the reflectivity of the second reflective layer is set to 99.5 to 99.8%, and the reflectivity of the third reflective layer is set to 99.9. % Is preferable.

Here, an example in which an ion assist film is used for a multilayer film is described. However, if the film is formed of an ion assist film, a durable and uniform film can be formed. Although it has the advantage of good film quality, film formation is not limited to ion-assist deposition, and multi-layer films formed by deposition, sputtering, ion plating, or other methods commonly used widely are usually used. Even if it is used, the present invention provides a great effect. The case where the layer H is mainly formed of T i 〇 ₂ (titanium dioxide) has been described. However, the present invention is not limited to this, and Ta ₂ 〇 ₅ (tantalum pentoxide) and Nb ₂ 〇 ₅ ( It may be formed of niobium pentoxide). Even in this case, the present invention has a great effect.

In FIG. 3, the incident light incident on the dielectric multilayer filter 300 has a different group velocity delay depending on what resonance phenomenon occurs in the cavities 311 and 312. By properly selecting the conditions, the required group velocity delay can be obtained.

Further, the delay time-wavelength characteristic of the group velocity delay of each wavelength of the reflected light obtained by the resonance can be changed also by adjusting the film thickness of each layer. It can be adjusted by changing the angle of incidence of the incident light on the dielectric multilayer filter.

In addition, even if the dielectric multilayer filter 300 has two or more cavities, it can be designed and manufactured, and can be manufactured in accordance with a desired delay time of each target wavelength.

The dielectric multilayer filter as described above is an example of the optical dispersion compensating element used in the present invention.

In addition, the group velocity delay time-wavelength characteristic curve of the dielectric multilayer film filter as the optical dispersion compensating element used in the present invention has a form capable of compensating for third-order dispersion as described later with reference to FIG. However, as described above, by changing the configuration of the multilayer film and the like, it is possible to make the form capable of compensating the second-order dispersion.

FIG. 4 is a graph showing the measured values of the light reflected by the dielectric multilayer filter 300. Reference numeral 51 denotes a measured group velocity delay time-wavelength characteristic curve, and the vertical axis represents the group velocity delay time. The horizontal axis is the wavelength. As can be seen from Fig. 4, this dielectric multilayer film 300 can obtain a maximum delay time of about 10 ps (picosecond) at a center wavelength of 1550 nm, and compensates for the third-order fraction. The bandwidth is about 0.4 nm. The multilayer filter used in the present invention transmits all the wavelengths in the wavelength band to be used (reflects when expressed as a multilayer film element), so that it has almost no power loss and is not shown. The insertion loss of the multilayer filter 300 shows a peak at the center wavelength, and its peak value is very low, less than 0.1 dB. Further, the multilayer filter used in the present invention does not generate dispersion ripple in a wavelength band for performing dispersion compensation. These are things that could not be expected with conventional dispersion compensation attempts.

As can be seen from the above example, the third-order or higher dispersion can be sufficiently compensated for by the third-order dispersion compensating element using the dielectric multilayer film of the present invention. In addition, it is possible to improve the characteristics of the signal light transmitted to the characteristics shown by the graphs 704 and 714 in FIG.

FIG. 5 is an explanatory diagram of a case where a chirp control is performed using a chirp generator 20 and a chirp reconstructor (that is, a dispersion compensator) 25. In FIG. 5, reference numeral 10 denotes an optical fiber or an optical fiber transmission system (hereinafter, also referred to as an optical fiber), 1 denotes a graph representing the amplitude characteristic of the signal light before being input to the chirp generator 20, and 2 denotes a graph. A graph showing the amplitude characteristics of the signal light being transmitted through the optical fiber 10, and 3 shows the amplitude characteristics of the signal light after being input to the chirp restorer 25 and subjected to chirp restoration (that is, dispersion compensation) and output. 11 is a graph showing the wavelength characteristic of the signal light before being input to the chirp generator 20, 12 is a graph showing the wavelength characteristic of the signal light being transmitted through the optical fiber 10, and 13 is a graph showing 15 is a graph showing the wavelength characteristics of signal light after being input to the chirp restoring unit 25, subjected to the chirp restoration and output. In graphs 1, 2, and 3, the vertical axis represents light intensity and the horizontal axis represents time. Graphs 11, 12, and 13 correspond to graphs 1, 2, and 3, respectively. The vertical axis shows the light intensity and the horizontal axis shows the wavelength. A communication system including an optical fiber 10 is connected between the chirp generator 20 and the chirp restoration unit 25 (not shown), and the signal light input to the chirp generator 20 is an optical signal. The chip is restored by the chip restoring unit 25 through the fiber 10 and output.

Hereinafter, embodiments of the present invention will be further described with reference to FIGS. 5 and 6. FIG. The signal light before input to the chirp generator 20 is As shown in 5 Daraf 1 and Daraf 11, the light intensity is high and the rate of change of the intensity is large. When such signal light is transmitted over a long distance, the intensity and wavelength of the light change and reception becomes impossible. However, the signal light input to the chirp generator 20 is chirped by the chirp generator 20, and the spectrum does not change as shown in graphs 2 and 12, but the light intensity is weak and the The rate of change of the intensity is also converted to a small signal light. Signal light having low light intensity and a small rate of change in intensity is not easily deformed, and has a small variation in light intensity and wavelength as in conventional low-speed communication. The signal light whose deformation is weak is converted by the chirp restoring unit 25 and output as almost the same signal light as the signal light input to the chirp generator 20.

From the above, by using the chirp generator 20 and the chirp decompressor 25 of the present invention for optical communication of long-distance transmission, the communication bit rate can be improved at the time of high-speed communication of 40 Gbps or more. Can communicate without any problem.

FIG. 6 is a diagram for explaining signal light during long-distance transmission in an optical fiber. The vertical axis represents the intensity of the signal light, and the horizontal axis represents time. Reference numerals 31, 32, and 33 denote signal light before being applied by the chirp generator, 41, 42, and 43 represent signal light that is applied by the chirp generator, and 40 denotes signal light 4. It is the graph which combined the intensity | strength of light of 1,42,43. In FIG. 6, the signal lights 31, 32, and 33 are sequentially and sequentially input to the chirp generator as shown. Then, the signal lights 31, 32, and 33 are capped by a cap generator, and change as shown by the signal lights 41, 42, and 43, respectively. The signal light 4 1, 4 2, and 4 3 in the optical fiber during long-distance transmission have a smaller temporal change rate of the light intensity than the signal light 3 1, 3 2, and 3 3. 1, 42, and 43 overlap the signal light before and after, and as shown in graph 40, the signal light appears to be almost constant in intensity. Therefore, even if the signal light is being transmitted through the optical fiber by some means, it looks like CW (continuous wave) noise as shown in Graph 40, and for example, a person trying to intercept the communication Even if you try to decode the signal, it is difficult to do so, and it has the highest security effects, such as preventing eavesdropping.

As described above, the configuration of FIG. 5 has been basically described. However, the present invention is not limited to this, and can also be applied to optical communication using wavelength multiplexing. For example, a signal light obtained by synthesizing a plurality of signal lights by a wavelength multiplexer is input to a chirp generator, and the signal light is input to a chirp generator. The signal light output from the transmission path is restored by a chirp restorer, input to the wavelength demultiplexer, and separated into a plurality of original signal lights. A system for transmitting light at high speed can be realized.

As another method, for example, a plurality of signal lights are respectively applied to a plurality of chirp generators to be chirped, and the plurality of chirped signal lights are multiplexed by a wavelength multiplexer and transmitted. After demultiplexing the signal light output from the transmission line by the wavelength demultiplexer, the signal light is restored to the original multiple signal lights by the multiple chirp decompressors corresponding to the multiple signal lights. It is possible to realize a system that performs high-speed communication while individually addressing security issues for each. In this case, the sender transmits to the receiver information on the type of the chirp for restoring the chirp, that is, the chirp information, and the receiver can restore the chirp of the received signal based on the chirp information. As a result, the usability, reliability, and security effects of the optical communication method according to the present invention and the optical communication device used therein become particularly remarkable.

Hereinafter, a case where the chirp control of the present invention is applied to an optical communication system using the above-described wavelength multiplexer will be described with reference to FIGS. 7 and 8.

FIG. 7 illustrates an optical communication system using a wavelength multiplexer and a wavelength demultiplexer. In FIG. 7, reference numeral 400 denotes an optical communication system, reference numerals 401, 402, 403, 425, and 426 denote a light source and a switch as transmitting devices, and reference numeral 404 denotes a transmitting device. Wavelength multiplexer, 405 is a wavelength demultiplexer, 406, 407, 408, 427, 428 are receivers as receivers (hereinafter also referred to as receivers) , 4 11, 4 12, 4 13, 4 14, 4 15, 4 16, 4 17, 4 18, 4 19 are transmissions using optical fibers or optical fiber systems 421, 422 are EDFAs (erpium 'dop fiber' amplifiers or optical amplifiers), and 423, 424 are ADMs.

Transmission lines 4 11, 4 12, 4 13, 4 14, 4 15, 4 16, 4 17, 4 18, 4 19 are equipped with a chip generator and a chip restoration. A chip control using the present invention can be applied to the optical communication system 400 by disposing a device. In addition, signal light can be transmitted and received to each point on the way by using ADM424 or ADM424. FIG. 8 is a diagram for explaining the signal lights multiplexed by the wavelength multiplexer 404 of FIG. 7. The vertical axis of the graph is time, and the horizontal axis is wavelength. The time on the vertical axis means going from a predetermined time to the future from above to below. Symbols 510, 520, 530 are signals generated by “light source + switch” 401, 402, 403, and multiplexed by the wavelength multiplexer 404. Light, 511 0, 5120, 5130 are the signals before being multiplexed by the wavelength combiner 4104 with the signals 5100, 520, 530, respectively. Each of the signal lights, 5 2 0, 5 2 0, and 5 2 3 0, which were combined by the wavelength combiner 4 04 after being chirped by the chirp generator, respectively, were the above-mentioned signal lights 5 0 1 0, 5 After the signals 0 0, 0 3 0 3 0 are multiplexed by the wavelength multiplexer 4 0 4, the signal light 5 0 1 0, 5 0 2 0, 5 0 3 0 is chirped by a signal generator with a signal light. is there. The symbols 510 1, 5 0 1 2, 5 0 1 3, ··· 'are the respective parts of the signal light 5 10 0 at time t 1 (that is, each channel, the same applies hereinafter), 5 0 2 1, 5 0 Are the parts of the signal light 520 at time t 2, 503 1, 503 2, 503 3,... Are the time t 3 Of the signal light 530 in FIG. That is, the signal light is transmitted in the order of 510, 520, 530 (the same applies hereinafter). The symbols 5 1 1 1, 5 1 1 2, 5 1 1 3 ... are parts of the signal light 5 11 0, 5 2 1 1, 5 1 2 2, 5 1 2 3. Reference numerals 1 230, 5 131, 5 13 2, 5 13 3 ··· are the parts of the signal light 5 130. Symbols 5 2 1 1, 5 2 1 2, 5 2 1 3 · 'are signal light 5 2 10 parts, 5 2 2 1, 5 2 2 2, 5 2 2 3 · ·' are signal light 5 2 20, 5 231, 5 232, 5 2 3 3... ′ Are the components of the signal light 5 230.

In the optical communication system 400, the signal light 511 0, 51200, 5130 is placed before the wavelength multiplexer 404, that is, “light source + switch” 4101. , 402, 403 or the transmission lines 411, 412, 413 and a signal light which has been subjected to a capture by being provided with a capture generator. The chirp decompressor can be arranged after the wavelength demultiplexer 405, that is, on the transmission lines 416, 417, 418, or at the wavelength demultiplexer 405 or before it. They can also be placed.

In the optical communication system 400, the signal light 5210, 5220, and 5230 are provided with a wavelength multiplexer 404 or a subsequent stage, that is, a chirp generator in the transmission path 414. This is a signal light that has been distributed and capped. As shown in FIG. 8, the signal light 510 is divided into signal wavelengths for each wavelength band, as indicated by 501, 510, 512, 513,. And multiple signal lights are mixed at the same time. Also, as with the signal light 510, the signal lights 520 and 530 also have signal lights separated for each wavelength band, and a plurality of signal lights are mixed at the same time. I have. The signal light 511 0 is applied to each of the signal lights 5 0 1 1, 5 0 1 2, 5 0 13,..., By a chirp generator, and the signal light is wavelength-converted. The signal lights multiplexed by the multiplexer 404 are capped at the same time as indicated by 5111, 5112, 5113, A plurality of signal lights are mixed. Further, the signal lights 5120 and 5130 also have a plurality of signal lights mixed at the same time, similarly to the signal light 5110. The signal light 5210 is a signal light obtained by inputting a signal light obtained by combining a plurality of signal lights by the wavelength multiplexer 404 into a chirp generator and applying a chirp. 5 2 1 1, 5 2 1 ■ 2, 5 2 1 3, · · ' Also, the signal lights 5220 and 5230 are configured as shown in the figure, similarly to the signal light 5210.

In addition to the above-described transmission using the chirp generator, the present invention has a great effect on the chirp recovery of the transmitted signal without using the chirp generator or without sufficient generation of the chirp. It demonstrates.

Note that, as described in the technical field of the present invention, the cap generator is a dispersion generator, and the cap reconstructor is a dispersion reconstructor and is a kind of dispersion compensator. It is clear from the above description.

As described above, the present invention has been described by taking the dielectric multilayer filter as an example. However, as described above, the present invention is not limited to this, and all ranges based on the technical idea of the present invention are included. Needless to say, it is.

The dielectric multilayer filter of the present invention is used as a third-order dispersion compensating element of the present invention in a communication device, and is used in a communication system using a DSF at a communication bit rate of 40 Gbps. Experiments have shown that the third-order dispersion can be sufficiently compensated so that the reception error due to the third-order dispersion, which has been a problem in the past, does not become a problem at all, and extremely good communication results were obtained. In particular, according to the present invention, the loss due to dispersion compensation is extremely small because the multilayer film element is used as the dispersion compensation element. This has a great effect that it is possible to construct a system in which dispersion compensation for each channel at the receiver stage is performed at 0.1 ldB or less.

According to the above description, the signal light incident on the third-order dispersion compensating element of the present invention is resonated by, for example, the cavities formed in the dielectric multilayer film, so that the delay different depending on the wavelength component of the output light with respect to the incident light. By properly selecting the conditions of the multilayer film, it is possible to realize the required group velocity delay and its bandwidth.

In addition, the conventional method of compensating for the secondary dispersion mainly generated in the transmission line by using a dispersion compensating fiber and the like, and the third-order dispersion compensation of the present invention or the second-order dispersion of the present invention By using the following dispersion compensation together, the present invention exerts a greater effect.

In the above, the method of the third-order dispersion compensation and the method of the second-order dispersion compensation have been mainly described in the present invention, taking the dielectric multilayer filter as an example, but one of the most remarkable features of the present invention. Is to compensate for the dispersion that occurs in signal light when transmitting over optical fibers, etc. with extremely low loss by using an optical dispersion compensating element, especially a tertiary or secondary optical dispersion compensating element using a multilayer film. , High speed and long distance communication. Further, one of the salient features of the present invention is that a dispersion generator (a chirp generator) and a dispersion reconstructor (a chirp reconstructor) are arranged in a communication system so that a signal light transmitted to an optical fiber can be captured. This means that the receiving side recovers the chirp and receives the data. For example, it is possible to reduce the variance that occurs during transmission or to increase the security during transmission.

The optical component of the present invention is an optical component having the above-described optical dispersion compensating element or optical dispersion generating element, or at least one of them.

The optical communication device according to the present invention is an optical communication device having a dispersion compensation function and a dispersion generation function by incorporating the optical components as described above, and includes, for example, a transmitter, an amplifier, a receiver, and various repeaters. Is one of them.

The optical communication method and the optical communication apparatus of the present invention can include a function of adding and decoding security information and a function of adding and decoding cap information. Include means to display and control information They can greatly improve optical communications over a wide range. Industrial applicability

INDUSTRIAL APPLICABILITY The communication method, the optical component, and the optical communication device according to the present invention can be widely used for optical communication, especially for high-speed, long-distance optical communication.

By using the element of the present invention that causes such a group velocity delay as a secondary or tertiary dispersion compensating element or a dispersion generating element in an optical communication system, the conventional dispersion compensation cannot compensate. The following chromatic dispersion can also be effectively compensated, and long-distance, high-speed optical communication can be realized without replacing all existing communication equipment such as optical fibers with new ones. In other words, the economic effect of the present invention is extremely large as compared with the method of replacing many communication facilities currently being considered with new ones.

Furthermore, the present invention significantly improves the security problem of optical communication, which has not been possible in the past, and encourages a new application field of optical communication.

Claims

The scope of the claims

1. In an optical communication method using an optical communication system using an optical fiber for a communication transmission line, the optical communication system includes at least one optical dispersion compensator (hereinafter, referred to as an optical dispersion compensator, It is simply called a dispersion compensator, which compensates for the dispersion caused by transmission through a fiber or the like, and based on the dispersion of the signal light transmitted after applying the dispersion to the signal light in advance as described later. In the present invention, a device having one or both of the functions of restoring, that is, restoring dispersion, is generically referred to as a dispersion compensator. An optical communication method, comprising: a dispersion compensator, a dispersion restoring device, etc.), wherein the dispersion of the output light from the optical fiber is compensated using the dispersion compensator.

2. The optical communication method according to claim 1, wherein the optical communication system has at least one optical dispersion generator (hereinafter, the optical dispersion generator is also simply referred to as a dispersion generator). An optical communication method, wherein the input light is subjected to dispersion using the dispersion generator and transmitted, and the dispersion of output light from the optical fiber is compensated using the dispersion compensator.

3. The optical communication method according to claim 1, wherein the optical communication system includes at least a signal light generator, a signal light output from the signal light generator, and a signal light transmitted from the signal light generator. A wavelength multiplexer for multiplexing the transmitted signal light, an optical fiber as an optical transmission line, an optical amplifier for amplifying the signal light being transmitted, and a signal light for transmitting the signal light transmitted through the optical fiber to each channel. A wavelength demultiplexer, which receives the signal light output from the wavelength demultiplexer, a dispersion generator, and the dispersion compensator. Input signal before input to optical fiber or optical fiber transmission system

An optical communication method, wherein (signal light) is dispersed by the dispersion generator.

4. The optical communication method according to claim 1, wherein a dispersion measuring device capable of measuring a dispersion value of the optical communication system is provided in the optical communication system.

5. The optical communication method according to claim 1, wherein the dispersion compensator is second-order or second-order or lower. It is necessary to have at least one of the above optical dispersion compensating element (hereinafter, the optical dispersion compensating element is also simply referred to as a dispersion compensating element) and at least one of the third- or higher-order dispersion compensating elements. Characteristic optical communication method.

6. The optical communication method according to claim 2, wherein the signal transmitted in the optical communication system includes dispersion information.

7. The optical communication method according to claim 2, wherein the dispersion generator and the dispersion compensator are manufactured based on the same principle, and the signal light output from the dispersion generator and transmitted through the optical fiber is the dispersion compensation. An optical communication method, wherein the optical signal is restored to the signal light before the dispersion input to the dispersion generator by the device.

8. The optical communication method according to claim 2, wherein the dispersion generator is a secondary or secondary or higher order light dispersion generating element (hereinafter, the light dispersion generating element is also simply referred to as a dispersion generating element. ) And at least one tertiary or third- or higher-order dispersion generating element.

9. In the optical communication method according to claim 3, when the communication bit rate of the input light to the optical fiber is 40 Gbps or more, the dispersion applied to the input light is such that the input light is an optical fiber or When the dispersion received in the process of transmitting the optical fiber transmission system is the same as the peak value of the input light without dispersion and the communication bit rate is 2.5 Gbps, the dispersion is applied to the input light. An optical communication method characterized in that the transmission is performed to a degree that is not greater than the deformation based on the dispersion received when the same optical fiber or optical fiber transmission system is transmitted over the same distance without using the same optical fiber or optical fiber transmission system.

10. The optical communication method according to claim 3, wherein the dispersion generator is provided between the signal light generator or the signal generator and the wavelength multiplexer.

11. The optical communication method according to claim 3, wherein the dispersion compensator is provided between the light receiver or the wavelength demultiplexer and the light receiver.

12. The optical communication method according to claim 3, wherein the dispersion generator is included in a wavelength multiplexer or an output-side transmission system of the wavelength multiplexer.

13. The optical communication method according to claim 3, wherein the dispersion compensator is included in a wavelength demultiplexer or an input side transmission system of the wavelength demultiplexer.

14. The optical communication method according to claim 3, wherein the dispersion is performed by the dispersion generator. An optical communication method, characterized in that the signal light contains information on security.

15. The optical communication method according to claim 4, wherein the dispersion generator and the dispersion compensator are manufactured based on different principles, and the dispersion compensation is performed in the dispersion compensator according to dispersion information. Characteristic optical communication method.

16. The optical communication method according to claim 5, wherein the dispersion compensating element is an element that performs dispersion compensation mainly using a multilayer film.

17. The optical communication method according to claim 8, wherein the dispersion generator includes an optical dispersion generation element formed of a multilayer film.

18. A component that can be used for optical communication using an optical fiber for the communication transmission line and that can change the chromatic dispersion of the secondary or higher order (hereinafter also referred to as dispersion) (hereinafter referred to as dispersion). In the following, the optical dispersion compensating element is also simply referred to as a dispersion compensating element, and the compensation of dispersion caused by transmission through a fiber or the like. According to the present invention, dispersion compensation is performed by dispersing the signal light in advance and returning the dispersion of the transmitted signal light, that is, restoring the dispersion, as described later. The elements are collectively referred to as elements, and when it is particularly necessary to distinguish or limit them, they are also referred to as dispersion compensation elements and dispersion restoration elements in a narrow sense.) Changing variance Optics least an optical component, characterized in that also have a one (hereinafter, also referred to as third-order dispersion compensation device).

19. The optical component according to claim 18, wherein at least one of the secondary dispersion compensating element and the tertiary dispersion compensating element is an element mainly composed of a multilayer film. Optical components.

20. The optical component according to claim 19, wherein the multilayer film is a dielectric multilayer film.

21. The optical component according to claim 19, wherein the thickness of each layer constituting the multilayer film is equivalent to a quarter of the central wavelength of the incident light when considered as the optical path length of the incident light. The optical component is characterized by being an integral multiple of the thickness (hereinafter, also referred to as “quarter wavelength”).

22. The optical component according to claim 19, wherein the multilayer film has at least three reflective layers having different reflectances, and each of the reflective layers has a refractive index at a quarter wavelength. Is composed of a plurality of sets of a combination of a relatively high layer (hereinafter also referred to as a layer H) and a layer having a quarter wavelength and a relatively low refractive index (hereinafter also referred to as a layer L). An optical component characterized in that:

23. The optical component according to claim 19, wherein the multilayer film has three or more reflective layers, and at least the first reflective layer and the second reflective layer are arranged in this order from the side where light is incident (input). An optical system, wherein a first cavity is formed between the second reflective layers, and a second cavity is formed between the second reflective layer and the third reflective layer. parts.

2 4. The optical component according to claim 19, wherein the multilayer film has at least three reflection layers, and is formed such that a distance as an optical path length between the reflection layers is different from each other. An optical component, characterized in that:

2 5. The optical component according to claim 19, wherein the multilayer film includes, in order from a light incident (input) side, at least a first reflective layer having a reflectance of 84 to 88%, 1 light transmission layer, having a second reflection layer with a reflectance of 99.5 to 99.8%, a second light transmission layer, and a third reflection layer with a reflectance of 99.9% or more An optical component, characterized in that:

2 6. The optical component according to claim 19, wherein the multilayer film includes at least three sets of a combination of layers H and L, and layers H and layers in order from the side where light is incident (input). 10 sets of combination layers of H, 1 layer of layer L, 9 sets of combination layers of layer H and layer L, 7 sets of combination layers of layer H and layer H, 1 layer of layer L, layer An optical component characterized in that a combination layer of H and layer L is formed in a set of 13 sets.

The optical component according to 2 7. Claim 2 0, the multilayer film is, T i 0 · (titanium dioxide) as the main, T a ₂ 〇 (tantalum pentoxide), N b O (niobium pentoxide) An optical component comprising: a layer containing at least one of the following; and a layer mainly containing Si ₂ (silicon dioxide).

2 8. The optical component according to claim 22, wherein the reflectance of each of the reflective layers is determined in the order of R 1, R, R 3, An optical component having a dispersion compensating element that satisfies R 1 ≤R 2 ≤R 3 where i of R i is an integer whose upper limit is the number of the reflective layers.)

29. The optical component according to claim 22, wherein the multilayer film is formed so as to have at least three reflective layers forming different cavities having different resonance wavelengths. parts.

30. A component used for optical communication that uses an optical fiber for the communication transmission line, and is an element (hereinafter referred to as secondary light) capable of providing secondary or secondary or higher chromatic dispersion (hereinafter also referred to as dispersion). Hereinafter, the light dispersion generating element is also simply referred to as a dispersion generating element) and an element capable of performing third- or higher-order dispersion (hereinafter, also referred to as a third-order dispersion generating element). An optical component characterized in that it has at least one of the functions described above, and has a function of a dispersion generator capable of dispersing signal light.

31. The optical component according to claim 30, wherein the function of the dispersion generator is exhibited by using a dispersion generating element having a multilayer film.

32. The optical component according to claim 31, wherein the multilayer film has at least two reflection layers.

33. The optical component according to claim 31, wherein the thickness of each layer constituting the multilayer film is equivalent to a quarter of the central wavelength of the incident light when considered as the optical path length of the incident light. An optical component characterized in that the thickness is an integral multiple of the thickness (hereinafter, also referred to as “quarter wavelength”).

34. The optical component according to claim 31, wherein the multilayer film has at least three reflective layers having different reflectances, and each of the reflective layers has a refractive index at a quarter wavelength. Is composed of a combination of a relatively high layer (hereinafter, also referred to as “layer H”) and a layer having a thickness of a quarter wavelength and a relatively low refractive index (hereinafter, also referred to as “layer L”). An optical component characterized in that:

3 5. An apparatus used for optical communication using an optical fiber as a communication transmission line, and an element (hereinafter referred to as secondary optical dispersion) capable of changing secondary or secondary or higher chromatic dispersion (hereinafter referred to as dispersion). In the following, the optical dispersion compensating element is simply referred to as a dispersion compensating element, and compensating for dispersion caused by being transmitted through a fiber or the like. In the present invention, a dispersion compensating element having one or both functions of restoring the dispersion of the transmitted signal light by applying dispersion to the signal light in advance, that is, restoring the dispersion, is collectively referred to in the present invention. And especially the ward When there is a need for another or limitation, they are also referred to as a dispersion compensating element and a dispersion restoring element in a narrow sense. An optical communication ia device comprising at least one of an element capable of changing the third-order or third- or higher-order dispersion (hereinafter, also referred to as a third-order dispersion compensating element).

36. The optical communication device according to claim 35, wherein the optical communication device has a plurality of dispersion compensation elements.

37. The optical communication device according to claim 35, wherein the optical communication device has at least one function of secondary dispersion compensation and tertiary or higher dispersion compensation. .

3 8. The optical communication device according to claim 35, further comprising at least one of a function of adding shared information and a function of reading shared information.

3 9. The optical communication device according to claim 35, wherein at least one of the dispersion compensating elements is an element mainly composed of a multilayer film.

40. The optical communication device according to claim 39, wherein the multilayer film has reflective layers having different reflectivities, and the reflectivities of the respective reflective layers are determined in order from a light incident (input) side. An optical communication device characterized by having a dispersion compensating element satisfying R 1 ≤R 2 ≤R 3 where R 1, R 2, R 3,.

41. The optical communication device according to claim 40, wherein each of the reflection layers has a thickness as an optical path length of a quarter wavelength of an input center wavelength (hereinafter, simply referred to as a quarter thickness). The layer having a higher refractive index (hereinafter also referred to as layer H) and the layer having a quarter wavelength and a lower refractive index (hereinafter also referred to as layer L). An optical communication device comprising a plurality of sets of combination layers.

4 2. The optical communication device according to claim 40, wherein the multilayer film has at least a first reflection layer having a reflectance of 84 to 88% in order from a side where light is incident (input), A first light transmitting layer, a second reflecting layer having a reflectivity of 99.5 to 99.8%, a second light transmitting layer, and a third reflecting layer having a reflectivity of 99.9% or more. An optical communication device comprising:

43. The optical communication device according to claim 40, wherein the multilayer film includes at least three sets of a combined layer of the layer H and the layer L and an order of at least three layers from the side where light is incident (input). layer 10 sets of combined layers of H, 1 layer of layer L, 9 sets of combined layers of layer H and layer L, 7 sets of combined layers of layer H and layer H, 1 layer of layer L, An optical communication device comprising a combination of layers H and L formed in a 13-set configuration.

4 4. A device used for optical communication using an optical fiber as a communication transmission line, and capable of providing secondary or secondary or higher chromatic dispersion (hereinafter also referred to as dispersion) (hereinafter referred to as secondary). Hereinafter, the light dispersion generating element is also simply referred to as a dispersion generating element) and an element capable of performing third- or higher-order dispersion (hereinafter, referred to as a third-order dispersion generating element). An optical communication device, comprising: a dispersion generator capable of dispersing signal light by using the dispersion generating element.

45. The optical communication device according to claim 44, wherein the function of the dispersion generator is exhibited by using a dispersion generator having a multilayer film.

46. The optical communication device according to claim 44, wherein the optical communication device has a plurality of dispersion generating elements.

47. The optical communication device according to claim 44, wherein the optical communication device can apply at least one of secondary or secondary and tertiary or tertiary or higher dispersion to the signal light. Special optical communication device.

4 8. The ability to apply chromatic dispersion (hereinafter simply referred to as “dispersion”) to the signal light transmitted through the optical fiber and the dispersion applied to the signal light and the dispersion generated in the process of transmitting the signal light. In an optical communication device having at least one of the functions that can be compensated for, information on dispersion such as dispersion to be applied to the signal light and the type of dispersion or the value of the dispersion applied or generated to the signal light. An optical communication device comprising: at least one of a means for displaying the information and a means for inputting the dispersion information for performing or compensating for the dispersion.