JP2006186407A - Optical cross-connect apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of transient response of the optical amplifier due to switching of an optical signal, and to enable high-speed switching in an optical cross-connect apparatus used in an optical network system including the optical amplifier. <P>SOLUTION: The optical cross-connect apparatus is provided on the optical network system for transmitting a wavelength multiplexed optical signal via an optical fiber transmission path and the optical amplifier, and switches the route of an optical signal of each wavelength of the wavelength multiplexed signal. This optical cross-connect apparatus is provided with a control means for controlling at least either the switching start timing of an optical signal of each wavelength or a time required for switching depending on the wavelength distance with an existing optical signal in switching for increasing/decreasing the optical signals of a plurality of wavelengths for the existing optical signal connected to a predetermined route. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical cross-connect device that switches wavelength-division multiplexed optical signals that are inserted into a plurality of optical fiber transmission lines including optical amplifiers and input / output to / from each optical fiber transmission line for each wavelength. The optical cross-connect device here may be any device that switches a wavelength multiplexed optical signal for each wavelength, and includes, for example, an optical add / drop device.

  In an optical network system using an optical wavelength path, an optical cross-connect device is used to connect a plurality of paths arbitrarily and realize a flexible configuration with respect to changes in line demand and ground.

  FIG. 12 shows a configuration example of a conventional optical cross-connect device (Patent Document 1). In FIG. 12 (1), an optical switch module 10 has N input ports and N output ports. Input optical signals 1 to N input from the input ports and output optical signals output from the output ports. 1 to N are connected one to one.

  In the optical cross-connect device shown in FIG. 12 (2), wavelength multiplexed optical signals are respectively input to M input ports, and are split into optical signals of respective wavelengths by the optical demultiplexer 11 and input to the optical switch module 10. Is done. The optical signals of each wavelength output from the optical switch module 10 are multiplexed by the optical multiplexers 12 corresponding to the M output ports, respectively, and wavelength multiplexed optical signals are output to the respective output ports. When the wavelength multiplexing number of each input / output port is T, the number N of input / output ports of the optical switch module 10 is M × T.

Here, as the optical switch module 10, for example, a three-dimensional MEMS (Micro Electro Mechanical Systems) optical switch shown in FIG. 13 is known. The three-dimensional MEMS optical switch is configured to be capable of N × N switching by driving and controlling the angle of the MEMS mirror using a pair of MEMS mirrors and an optical fiber array.
JP-A-6-292246

  By the way, in an optical network system including such an optical cross-connect device, an optical amplifier 14 for compensating for signal power attenuation due to loss in the optical fiber transmission line 13 is generally used as shown in FIG. is there. The optical amplifier 14 can amplify a plurality of single or wavelength multiplexed optical signals within the optical amplification band. However, it is known that a transient response occurs due to the presence or absence of input light or a change in optical power, and a gain change occurs with respect to an optical signal passing therethrough.

  Such a transient response of the optical amplifier becomes more prominent as the speed of fluctuation of the input signal power is closer to the gain relaxation time of the optical amplifier. This gain relaxation time is, for example, about several ms in the case of the most commonly used erbium-doped optical fiber amplifier, and generally varies depending on the type of optical amplifier used or operating conditions such as saturation intensity.

  On the other hand, the switching time of a general optical switch such as the above-described three-dimensional MEMS switch is about several ms or more. Therefore, in an optical switch, it is common to avoid the influence of the transient response of the optical amplifier by switching at a speed sufficiently slower than the gain relaxation time of the optical amplifier.

  In an optical cross-connect device used in an optical network system including an optical amplifier, the present invention reduces the influence of the transient response of the optical amplifier accompanying optical signal switching and enables high-speed switching. An object of the present invention is to provide an optical cross-connect device capable of ensuring high performance and high reliability and improving operability.

  A first invention is an optical cross-connect device that is arranged in an optical network system that transmits a wavelength-multiplexed optical signal via an optical fiber transmission line and an optical amplifier, and switches the optical signal path of each wavelength of the wavelength-multiplexed optical signal. When switching to increase / decrease the optical signal of multiple wavelengths with respect to the existing optical signal connected to the predetermined path, the optical signal of each wavelength is changed according to the wavelength interval with the existing optical signal. Control means for controlling at least one of the switching start timing and the switching required time is provided.

  When the control means in the optical cross-connect device of the second invention performs switching to increase / decrease optical signals of a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path, In this configuration, switching is performed by sequentially delaying the switching start timing in order of increasing wavelength interval.

  When the control means in the optical cross-connect device of the second invention performs switching to increase / decrease optical signals of a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path, In this configuration, switching is performed such that the required switching time becomes longer in order of increasing wavelength interval.

  The control means in the optical cross-connect device according to the fourth aspect of the present invention is configured to switch from an existing optical signal when switching to increase or decrease an optical signal having a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path. In this configuration, the switching start timing is sequentially delayed in order of increasing wavelength intervals, and the switching is performed so that the required switching time becomes longer.

  The fifth invention has a function of receiving and notifying information such as the number of optical amplifiers connected to the optical network system, the characteristics of each optical amplifier, and operating conditions as a control means, and holding and updating the information. A configuration is adopted in which switching control of optical signals of a plurality of wavelengths is performed based on information.

  The optical cross-connect device of the present invention performs switching to increase / decrease optical signals of a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path in order of increasing wavelength interval from the existing optical signal. By sequentially delaying the switching start timing and switching, the influence of the transient response on the existing optical signal of the optical amplifier connected to the optical cross-connect device can be minimized.

  In addition, when switching to increase / decrease optical signals of multiple wavelengths with respect to an existing optical signal connected to a predetermined path, the required switching time becomes longer in order of increasing wavelength interval from the existing optical signal. By switching in such a manner, it is possible to minimize the influence of the transient response on the existing optical signal of the optical amplifier connected to the optical cross-connect device, and to shorten the time required for switching.

  In addition, by performing switching based on information such as the number of optical amplifiers connected to the optical network system, the characteristics and operating conditions of each optical amplifier, optimal control is performed for the effects of transient responses on the existing optical signals of the optical amplifier. Can do.

(First embodiment)
FIG. 1 shows a first embodiment of the optical cross-connect device of the present invention. In the figure, wavelength multiplexed optical signals are respectively input to M (here, M = 2) input ports, and are demultiplexed into optical signals of respective wavelengths by optical demultiplexers 11-1 and 11-2. 10 is input. The optical signals of each wavelength output from the optical switch module 10 are multiplexed by the optical multiplexers 12-1 and 12-2 respectively corresponding to the M output ports, and wavelength multiplexed optical signals are respectively output to the output ports. Is output. Each output port of the optical cross-connect device is connected to a terminal device (not shown) or the next optical cross-connect device (not shown) via optical fiber transmission lines 13-1 and 13-2 and optical amplifiers 14-1 and 14-2. (Not shown) is connected.

  In the present embodiment, the optical switch control unit 15 that controls the order and switching start timing when switching optical signals of a plurality of wavelengths at each output port of the optical switch module 10 is provided. Here, for ease of explanation, the wavelength-division multiplexed optical signal input to the optical demultiplexer 11-1 is assumed to be two waves, which are output as they are to the optical multiplexer 12-1, and then to the optical demultiplexer 11-2. The input wavelength-multiplexed optical signal is assumed to be four waves and is initially output to the optical multiplexer 12-2, but it is assumed that all four waves are switched to the optical multiplexer 12-1 thereafter. As shown in FIG. 2, the wavelengths of the wavelength multiplexed optical signals input to the optical demultiplexers 11-1 and 11-2 are λt1, λt2, and λs1, λs2, λs3, and λs4, respectively. Conventionally, four waves input to the optical demultiplexer 11-2 are simultaneously switched from the optical multiplexer 12-2 to the optical multiplexer 12-1, but in this embodiment, a time difference is provided for switching the four waves. Switch in order.

  Here, the transient response of the optical amplifier will be described. The transient response is due to the fact that the inversion distribution state of the optical amplifier changes depending on the state of the input signal. The spectral characteristics of this inversion distribution state are governed by two factors generally called uniform spread and non-uniform spread. The uniform spread is determined mainly by the excited state lifetime of the atoms involved in the light absorption and emission of the light amplification medium, and has a certain spectral shape. When an optical signal is incident on such an optical amplifier having only a uniform spread, an inductive transition that is determined only by the incident light intensity and the uniform spread spectral distribution occurs, and as shown in FIG. Gain saturation occurs as the distribution changes. Fig. 3 shows a uniform spread spectrum when no signal is input and a uniform spread spectrum when a signal is input. (1) and (2) are located at the center of the spectrum even if the input signal light intensity is the same. It shows that saturation intensity differs depending on whether or not. That is, when the input signal light wavelength deviates from the center of the gain spectrum (FIG. 3 (2)), the saturation intensity becomes small.

  On the other hand, the non-uniform spread of the spectral characteristics of the inversion distribution state is caused by the fact that the state of the atoms involved in the light absorption and emission of the optical amplifying medium becomes non-uniform due to distortion and the like, and the transition frequency has a certain distribution. Most optical amplification media generally have both this uniform spread and non-uniform spread, and as a result, the gain spectrum of the optical amplifier is determined by the combination of both as shown in FIG.

  When an optical signal having a single wavelength is input to an optical amplifier having such a gain spectrum, the optical amplifier gain causes a particularly strong inversion distribution change in the vicinity of the signal light wavelength. As a result, as shown by the broken line in FIG. 5, the gain spectrum has a strong saturation characteristic only around this wavelength and around it. In other words, optical signals within the uniform spread width of this gain spectrum are strongly affected by each other's gain saturation, while signals at distant wavelength positions are relatively less affected by each other's presence. I understand.

  Based on the above principle, in FIG. 1 and FIG. 2, in the situation where the optical signals of the wavelengths λt1 and λt2 are combined by the optical multiplexer 12-1 and input to the optical amplifier 14-1, the wavelengths λs1, λs2 , Λs3, λs4 will be described with reference to FIG. 6 in the case of increasing the number of wavelengths for switching the optical signals from the optical multiplexer 12-2 to the optical multiplexer 12-1. In the situation where the optical signals of wavelengths λt1, λt2, λs1, λs2, λs3, and λs4 are combined by the optical multiplexer 12-1 and input to the optical amplifier 14-1, the wavelengths λs1, λs2, λs3, The same applies to the case of decreasing the number of wavelengths for switching each optical signal of λs4 from the optical multiplexer 12-1 to the optical multiplexer 12-2. Here, among the optical signals input to the optical amplifier 14-1, the optical signals of the wavelengths λt1 and λt2 that are not changed by switching are referred to as “existing optical signals”.

  As shown in FIG. 6 (1), the optical signal having the wavelength λs1 is close to the existing optical signals having the wavelengths λt1 and λt2, and therefore these signals are present within the range of the uniform spread. Become. Therefore, when an optical signal having a wavelength λs1 is newly added to the optical amplifier 14-1, a transient response is caused by this change in signal power, and the existing optical signals having wavelengths λt1 and λt2 are strongly affected. On the other hand, as shown in FIG. 6 (2), since the optical signal of wavelength λs4 is separated from the existing optical signals of wavelengths λt1 and λt2, these signals must be outside the range of uniform spread of each other. become. Therefore, even if an optical signal having a wavelength λs4 is newly added to the optical amplifier 14-1, the transient response due to the change in signal power does not greatly affect the existing optical signals having the wavelengths λt1 and λt2. As described above, the influence of the increase or decrease in the number of input signal wavelengths to the optical amplifier on the existing optical signal is larger as the wavelengths are closer to each other.

  In general, the ratio increases as the ratio of the increasing / decreasing number of signals to the number of existing signals increases. For example, when one signal is added to a single wavelength signal when the number of existing signals is 100, the influence is greater than when one signal is added.

  From the above, it can be seen that when optical signals with a plurality of wavelengths are increased / decreased relative to an existing optical signal, it is better to switch the optical signals with a plurality of wavelengths one by one rather than simultaneously. At that time, it is necessary to consider that the influence of the optical signal to be switched first is the largest.

  Therefore, in the present embodiment, as shown in FIG. 7, the optical signal having the wavelength λs4 which is located farthest from the existing optical signals having the wavelengths λt1 and λt2 and has the least influence of the switching is switched first, and then the wavelength allocation Switching with a time difference in order of distance. Thereby, it is possible to minimize the influence on the existing optical signals of the wavelengths λt1 and λt2 due to the switching of the optical signals of the wavelengths λs1, λs2, λs3, and λs4.

(Second Embodiment)
In the first embodiment, the switching characteristics indicating the relationship between the switching time required for each wavelength and the optical output in the optical switch module 10 are the same, the switching start timing is provided with a time difference, and switching is performed in a predetermined wavelength order. .

  In the present embodiment, as the required switching time (switching rise time) becomes shorter, the influence of the transient response of the optical amplifier becomes larger. Therefore, a difference is provided in the required switching time corresponding to each wavelength, and the switching is performed in a predetermined wavelength order. And The configuration of the optical cross-connect device, the number of signal wavelengths, the wavelength arrangement, and the like are the same as those in the first embodiment, and the optical switch control unit 15 controls the required switching time and order for each wavelength.

As shown in FIG. 8, the switching of the signal light in the present embodiment is the time required for switching the optical signal of the wavelength λs4 which is in the wavelength arrangement farthest from the existing optical signals of the wavelengths λt1 and λt2 and has the least influence of the switching. The shortest trs4 is set, and the required switching time is lengthened in the order of increasing wavelength arrangement. That is, when the required switching times of the optical signals of wavelengths λs1, λs2, λs3, and λs4 are trs1, trs2, trs3, trs4,
trs1>trs2>trs3> trs4
Control to be As a result, the influence on the existing optical signals of the wavelengths λt1 and λt2 associated with the switching of the optical signals of the wavelengths λs1, λs2, λs3, and λs4 can be minimized, and the entire time required for switching can be shortened. It becomes possible.

(Third embodiment)
FIG. 9 shows an example of signal light switching according to the third embodiment. In this embodiment, when combining the first embodiment and the second embodiment and increasing / decreasing an optical signal having a plurality of wavelengths with respect to an existing optical signal, in order from the farthest from the wavelength of the existing optical signal, Control is performed so that the switching start timing is delayed and the required switching time is lengthened. As a result, it is possible to reduce the overall time required for switching, rather than making the required switching time corresponding to each wavelength uniform as in the first embodiment.

(Fourth embodiment)
The transient response accompanying the fluctuation of the number of input signal wavelengths in the optical amplifier becomes more prominent as the number of connected optical amplifiers increases. In addition, the transient response time depends on parameters such as operating conditions such as characteristics of the optical amplifier used, the number of input signal wavelengths, input signal power, and gain.

  In this embodiment, as shown in FIG. 10, for example, information such as characteristics and operating conditions is transferred to the optical switch control unit 15 from each optical amplifier 14 connected to the output port of the optical cross-connect device using a control channel. . The optical switch control unit 15 has a function of holding the information and updating the information when there is a change. Based on the information, the order corresponding to each wavelength, the switching start timing, the required switching time, and the like are based on the above embodiment. Control is performed so that the influence of the transient response is minimized and the time required for switching is minimized.

  10 shows an example in which information is transferred from each optical amplifier 14 to the optical switch control unit 15 using a control channel. For example, the terminal device 16 collects information in each optical amplifier and controls the optical switch. When the information is transferred to the unit 15 or the information to be transferred is limited to the number of input signal wavelengths, it may be transferred from a part of the optical amplifier 14 or the terminal device 16 to the optical switch control unit 15. .

  Further, instead of using the control channel, as shown in FIG. 11, necessary information may be transferred to the optical switch control unit 15 using the opposite line.

The figure which shows 1st Embodiment of the optical cross-connect apparatus of this invention. The figure which shows the example of signal wavelength arrangement | positioning. The figure which shows the characteristic in case the gain spectrum of an optical amplifier has only uniform spread. The figure which shows the characteristic in case the gain spectrum of an optical amplifier has uniform spread and non-uniform spread. The figure which shows the characteristic of the optical amplifier at the time of the optical signal input of a single wavelength. The figure which shows the relationship of the uniform spread spectrum of the existing optical signal and a switching optical signal. The figure which shows the example of signal light switching of 1st Embodiment. The figure which shows the example of signal light switching of 2nd Embodiment. The figure which shows the example of signal light switching of 3rd Embodiment. The figure which shows the structural example of 4th Embodiment. The figure which shows the modification of 4th Embodiment. The figure which shows the structural example of the conventional optical cross-connect apparatus. The figure which shows the structural example of a three-dimensional MEMS optical switch. The figure which shows the structural example of an optical network system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical switch module 11 Optical demultiplexer 12 Optical multiplexer 13 Optical fiber transmission line 14 Optical amplifier 15 Optical switch control part 16 Terminal station apparatus

Claims (5)

In an optical cross-connect device that is arranged in an optical network system that transmits a wavelength-multiplexed optical signal via an optical fiber transmission line and an optical amplifier, and switches the path of the optical signal of each wavelength of the wavelength-multiplexed optical signal,
When switching to increase or decrease the optical signal of multiple wavelengths with respect to the existing optical signal connected to a predetermined path, switching of the optical signal of each wavelength according to the wavelength interval with the existing optical signal An optical cross-connect device comprising control means for controlling at least one of start timing and time required for switching. The optical cross-connect device according to claim 1,
When the control means performs switching to increase / decrease optical signals of a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path, the switching start timing in descending order of wavelength intervals from the existing optical signal. An optical cross-connect device characterized in that the switching is performed by sequentially delaying. The optical cross-connect device according to claim 1,
When the control means performs switching to increase or decrease an optical signal having a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path, the switching time is increased in order of increasing wavelength interval from the existing optical signal. The optical cross-connect device is characterized in that the switching is performed so that the length becomes longer sequentially. The optical cross-connect device according to claim 1,
When the control means performs switching to increase / decrease optical signals of a plurality of wavelengths with respect to an existing optical signal connected to a predetermined path, the switching start timing in descending order of wavelength intervals from the existing optical signal. The optical cross-connect device is characterized in that the switching is performed so that the switching time is sequentially delayed and the switching time is sequentially increased. In the optical cross-connect device according to any one of claims 1 to 4,
The control means receives a notification of information such as the number of optical amplifiers connected to the optical network system, the characteristics and operating conditions of each optical amplifier, and has a function of holding and updating the information based on the information. The optical cross-connect device is configured to perform switching control of the optical signals of the plurality of wavelengths.

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