CN101273557A - Monitoring optical transmission method for wavelength division multiplexing transmission system and wavelength division multiplexing transmission apparatus - Google Patents
Monitoring optical transmission method for wavelength division multiplexing transmission system and wavelength division multiplexing transmission apparatus Download PDFInfo
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- CN101273557A CN101273557A CNA2005800516480A CN200580051648A CN101273557A CN 101273557 A CN101273557 A CN 101273557A CN A2005800516480 A CNA2005800516480 A CN A2005800516480A CN 200580051648 A CN200580051648 A CN 200580051648A CN 101273557 A CN101273557 A CN 101273557A
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Abstract
In a wavelength multiplex transmission system having transmission paths (5a, 5b) for transmitting a wavelength multiplex light as a main signal light, a monitoring control light is transmitted in the direction reverse to the transmission direction of the main signal light in the light transmission paths (5a, 5b). This suppresses attenuation of the monitoring control light by the Raman scattering phenomenon and increases the relay distance.
Description
Technical field
The present invention relates to monitor optical transmission method and Wavelength division multiplexing transmission apparatus in the wave division multiplexing transmission system, particularly be suitable in the main signal light of a plurality of wavelength by the technology of the long distanceization of the transmission range of the monitor optical of wavelength division multiplexing.
Background technology
In recent years, follow the high capacity of communication, wavelength division multiplexing (WDM:Wavelength DivisionMultiplexing) transmission system (hereinafter referred to as the WDM transmission system) is popularized.In this WDM transmission system, flashlight for the long a plurality of wavelength of Distance Transmission (channel), the loss that needs the adequate compensation flashlight in transmitting, to be subjected to optical fiber, therefore, not only dispose post amplifier and the such amplifier of preamplifier in forwarding office and the office of acceptance, also with the relaying of the arranged spaced tandem office about tens km～over one hundred km with image intensifer [for example EDFA (Erbium DopedFiber Amplifier: erbium-doped fiber amplifier) or raman amplifier etc.], carry out the amplification of flashlight repeatedly, realize long Distance Transmission thus.
And, recently, (Optical Add/Drop Multiplexer: optical add/drop multiplexer) node is also in continuous increase for the OADM of any wavelength (channel) of branch/insertion (Drop/Add) in tandem office, under this situation, except relaying with the image intensifer, also dispose the such function element of optical switch or multiplexer/demultiplexer (below be sometimes referred to as the unit).
In these unit for example is under the situation of amplifier, during at the initial start of system, when the channel increase and decrease is set or the situation of the circuit broken string that in system employs, produces, control signal such as need suitably give starting, gain controlling from the outside, open circuit is controlled to be optimum state with system.
Therefore, in the WDM transmission system, be independent of main signal light and come transmitting, monitoring signal [below be sometimes referred to as SV (Supervisory) light or SV signal], by this SV light, for example with each tandem office interval as a unit, carry out each interval condition monitoring, and from the tandem office of upstream side (or downstream) tandem office's conveyer system information of side (or upstream side) downstream, according to these information, above-mentioned each unit of optimal control.The transmission means of this SV light has variety of way, as general structure example, for example as shown in Figure 7, has the Wavelength Assignment SV light different with main signal light is carried out transmission manner.
When being conceived between certain relay area, for example this existing WDM transmission system shown in Figure 7 constitutes and has: a plurality of 10h of tandem office, 10i, 10j ... (tandem office beyond the 10h of tandem office, 10i, the 10j omits diagram, below, be designated as " tandem office 10 " in the situation following table of not distinguishing them); And, the office that can continue in these is connected light transmission path (optical fiber) 50a of up (the paper right of Fig. 7) usefulness between each tandem office 10 and the light transmission path 50b of descending (the paper left of Fig. 7 to) usefulness for carrying out bidirectional optical between 10.
And each tandem office 10 has: the image intensifer 20b that is used to amplify the image intensifer 20a of up main signal light and is used to amplify descending main signal light; Be used for the SV light partial wave that carried out partial wave by the SV light of wavelength division multiplexing with up main signal light at up WDM light with coupler 40a be used for being carried out the SV light partial wave coupler 40b of partial wave by the SV light of wavelength division multiplexing with descending main signal light at descending WDM light; And be used for the photosynthetic ripple of SV of the photosynthetic ripple SV of descending main signal light with coupler 70a be used for the photosynthetic ripple of SV coupler 70b the photosynthetic ripple SV of up main signal light.
And each tandem office 10 also has: will utilize SV light partial wave to be converted to light/electricity (O/E) transducer 100a of the signal of telecommunication with coupler 40a up SV light of partial wave from up WDM light; The SV light that utilizes SV light partial wave with coupler 40b partial wave from descending WDM light is converted to light/electricity (O/E) transducer 100b of the signal of telecommunication; Will from aftermentioned handling part 90a descending with the SV conversion of signals be suitable for utilizing the photosynthetic ripple of SV with coupler 70a in descending main signal light by electricity/light (E/O) transducer 80a of the flashlight of wavelength division multiplexing (SV light); And will from aftermentioned handling part 90b up with the SV conversion of signals be suitable for utilizing the photosynthetic ripple of SV with coupler 70b in up main signal light by electricity/light (E/O) transducer 80b of the flashlight of wavelength division multiplexing (SV light).
And then each tandem office 10 also has: being used to carry out various processing serves as handling part 90a, the 90b that the form of usefulness was used and controlled in transmission with for example SV conversion of signals of the signal of telecommunication; And be used for these handling parts 90a, 90b communicates by letter and according to the unit controls portion 130 that receives each unit of SV signal controlling (being image intensifer 20a, 20b here).
In the existing system that constitutes as mentioned above, for example, control is configured in the needed control information in unit ( image intensifer 20a, 20b) among the 10i of tandem office, utilize handling part 90a, 90b to be converted to the SV signal from unit controls portion 130, and then, utilize E/ O transducer 80a, 80b that this SV conversion of signals is the SV light as light signal, pass out to optical fiber 50a, 50b with coupler 70a, 70b via the photosynthetic ripple of the SV of downlink side and upstream side.
This SV light is via optical fiber 50a, 50b, be transferred to the 10h of tandem office (being seen as main signal light downlink side) and the 10j of tandem office (being seen as main signal light upstream side) of hypomere from the 10i of tandem office from the 10i of tandem office, in the 10h of each tandem office, 10j, utilizing SV light partial wave is SV light and main signal light with coupler 40b, 40a partial wave, main signal light utilizes image intensifer 20b, 20a to amplify, and SV light is output to O/E transducer 100b, 100a.
Then, SV light is converted into the SV signal as the signal of telecommunication in O/E transducer 100b, 100a, output to handling part 90b, 90a then, and then, output to the unit controls portion 130 that is used for controlling the unit ( image intensifer 20a, 20b) that is configured in the 10h of tandem office, 10j.
As mentioned above, by transmitting SV light with main signal light in optical fiber 50a, 50b, the information relevant with the status transmission between each tandem office 10 is shared between each tandem office 10.
For example, above-mentioned this method was applied between each tandem office 10 in the past, when the initial start of system, by pass on above-mentioned SV light successively from the tandem office 10 of upstream side, from the tandem office 10 of upstream side starting unit successively, perhaps, when optical fiber 50a, 50b break, for safety, by SV light from the tandem office 10 that detects broken string upstream the tandem office 10 of side notify this meaning, the output (output of image intensifer 20a, 20b) of the tandem office 10 of upstream side is opened circuit, and thus, is optimization with each unit controls.
But in recent years, the increase along with the channel quantity of WDM signal causes harmful effect to this SV light.Particularly, the power transfer of SV light is in main signal light in light transmission path 50a, 50b, and the link budget of SV light (difference of transmission level and incoming level) becomes problem, has the problem that the distance between each tandem office 10 is restricted.This problem is to be that the Raman scattering phenomenon causes by one of non-linear phenomena that produces in optical fiber 50a, 50b.
Here, use Fig. 8 that Raman scattering phenomenon (Raman gain) is described briefly.
In this curve chart shown in Figure 8, the longitudinal axis is represented the power of optical fiber input light and based on the Raman gain of Raman scattering phenomenon, transverse axis is represented wavelength, and this curve chart is the power of expression optical fiber input light (Raman exciting light) and based on the curve chart of the wavelength characteristic of the Raman gain of Raman scattering phenomenon.
By this Fig. 8 as can be known, in optical fiber during the powerful coherent light of incident, at the illustrated Raman gain band of region generating of wavelength to about long wavelength side skew 100nm from optical fiber input light (Raman exciting light).Under the little situation of the power of optical fiber input light, the level of this Raman gain band is little of negligible degree, and still, along with the power change of incident light is big, it is big that the influence of non-linear phenomena becomes, and the level of this Raman gain band is big to the degree that can't ignore.
And when there were other powerful light (being exaggerated light) in this Raman gain band, this was exaggerated light and amplifies from incident light predation power.That is, incident light is replaced into SV light, will be exaggerated the main signal light time that light is replaced into WDM light, during propagating in optical fiber 50a, 50b, the power transfer of SV light is to main signal light, so assignable loss value reduces appropriate section in loss of transmission paths.
Here, the power of main signal light is maximum near the transmission output of tandem office 10, then, along with the propagation in optical fiber 50a (50b), because the influence of loss of transmission paths, power reduces, so, near the above-mentioned transmission output that the main signal luminous power is big, the SV luminous power is many more to the power that main signal light shifts, and the SV luminous power significantly reduces.
That is, in WDM transmission system for example shown in Figure 9, near the output of the transmission shown in the label 101, significantly produce reduction based on the SV luminous power of Raman scattering phenomenon.In addition, in this Fig. 9, the parts of the label identical have been marked with label shown in Figure 7, be respectively and the identical or the same parts of the described parts of Fig. 7, SV optical transmitter 60 among the 10h of tandem office (10i) is equivalent to the piece by the handling part 90b of Fig. 7 and E/O transducer 80b (handling part 90a and E/O transducer 80a) formation, and the SV optical receiver 30 among the 10i of tandem office is equivalent to the piece by handling part 90a and O/E transducer 100a (handling part 90b and O/E transducer 100b) formation equally.
Use the range performance figure of the variable power of expression main signal light shown in Figure 10 and SV light that this situation is described.
In this curve chart shown in Figure 10, the longitudinal axis is represented the power of main signal light and SV light, and transverse axis is represented the lengthwise location of light transmission path 50a (50b), in above-mentioned example, the left end of transverse axis is represented the 10h of tandem office (10i), and the right-hand member of transverse axis is represented the 10i of tandem office (10j).Main signal light when in addition, the dotted line among this Figure 10 is represented not produce the Raman scattering phenomenon and the variable power of SV light.
By this curve chart as can be known, the Raman scattering phenomenon mainly is created near the also smaller 10h of tandem office (10i) (forwarding office) of the transmission loss of light transmission path 50a (50b), near this, the power transfer of SV light is to main signal light, the power of main signal light (based on the mean value of channel quantity) is exaggerated, on the other hand, the power of SV light reduces.Its result, the power of the SV light among the 10i of tandem office (10j) (office of acceptance) is subjected to the influence of the transmission loss of light transmission path 50a (50b), compares with main signal light significantly and reduces.
Therefore, for example as shown in figure 11, even in certain tandem office 10, generate each the channel signal light and the SV light (with reference to the left side of Figure 11) of main signal light respectively with identical level, in the tandem office 10 of hypomere (receiver side), be subjected to the influence of the Raman scattering phenomenon among the light transmission path 50a (50b), the power of main signal light increases, and on the other hand, the power of SV light significantly reduces (with reference to the right side of Figure 11).In addition, dotted line and Figure 10 in the tandem office 10 of receiver side (right side of Figure 11) are same, the main signal light when expression does not produce the Raman scattering phenomenon and the power (incoming level) of SV light.And in the tandem office 10 (right side of Figure 11) of receiver side, the power increase of the channel signal light that wavelength is long more is many more, and this is because as shown in Figure 8, the Raman gain band has the distribution character of wavelength dependency.
As mentioned above, in the WDM transmission system, when there is main signal light (being exaggerated light) in Raman gain band shown in Figure 8, during in light transmission path 50a, 50b, propagating, the power transfer of SV light is to main signal light, so assignable loss value reduces appropriate section in loss of transmission paths.That is, the link budget of SV light becomes problem, and the maximum loss between the admissible tandem office of system is restricted.In big capacity WDM transmission system in recent years, the channel quantity of main signal light reaches more than 100 channels sometimes, has the also many more problems of power reduction of channel quantity many more (quantity that is exaggerated light is many more) SV light.
At this problem, can consider following method: the SV light wavelength is set at the wavelength that SV light and main signal light are not subjected to the influence of Raman scattering phenomenon.For example can consider to select to depart from wavelength more than the 100nm as the SV light wavelength, perhaps, set SV light wavelength etc. at the long wavelength side of main signal light from the wave band of main signal light.
And, also have following technology: in order to compensate the power reduction of SV light, be prerequisite, increase the power of transmitter side in advance as far as possible, transmit then to produce the Raman scattering phenomenon.
And,, also can consider SV light not to be distributed special-purpose wavelength and the mode (for example with reference to following patent documentation 1,2) of the SV light that superposes in main signal light as additive method.
In addition,, also can consider following technology: in the light transmission path of transmission main signal light, append channel, with the two-way communication (for example with reference to following patent documentation 3) of carrying out SV light as the technology of transmitted in both directions SV light.
Patent documentation 1: TOHKEMY 2003-114453 communique
Patent documentation 2: TOHKEMY 2003-32193 communique
Patent documentation 3: TOHKEMY 2001-358665 communique
But, for example as shown in figure 12, light transmission path (optical fiber) 50a, 50b generally have the loss characteristic of following wavelength dependency: promptly, near transmission loss minimum 1560～1580nm, in addition, it is big more to depart from transmission loss from this wave band more, considers this characteristic, in the described also existing problems that the SV light wavelength are set in the method for wavelength of influence that SV light and main signal light is not subjected to the Raman scattering phenomenon.
Promptly, the wave band of main signal light mainly utilizes the minimum and C-band that can be easily the light of this wave band be amplified of loss (1530nm～1565nm) and L-band (1565nm～1625nm), so, when wanting under this condition, to select the SV light wavelength, the preferred wavelength of selecting the wave band loss minimum in addition of main signal light, so, the short wavelength side that inevitable choice and C-band are adjacent.Therefore, as mentioned above, selecting to depart from wavelength more than the 100nm as the SV light wavelength from the wave band of main signal light, perhaps, set in the such method of SV light wavelength, at the long wavelength side of main signal light even remove the influence of Raman scattering phenomenon, the loss that is subjected in transmission path also has more appropriate section, so the link budget that still has SV light becomes problem, the problem that the distance between the tandem office is restricted.
And then, shown in above-mentioned method, in order to compensate the power reduction of SV light, to produce the Raman scattering phenomenon is prerequisite, increases the power of transmitter side in advance, under the situation about transmitting then as far as possible, not only Raman scattering phenomenon, other non-linear phenomenas are that the influence of stimulated Brillouin scattering also becomes significantly, so SV trimmed book body possibly can't transmit.And, in order to produce high-power SV light, need the light-emitting component (LD) of the big high price of power output, so also undesirable aspect cost.
And, shown in patent documentation 1,2 methods of being put down in writing, under the situation that stack SV light transmits in main signal light, the transmission loss of main signal light and SV light equates, so, solved the problem of the link budget of SV light, but, in order to transmit the SV signal, must be with certain main signal light by being prerequisite, so, for example main signal light does not also pass through when the initial start of system, therefore, even remembering that moving cell also can't transmit becomes the SV of its triggering signal light, have can't starting unit problem.
And then, shown in the method that patent documentation 3 is put down in writing, even transmit under the situation of SV light in light transmission path, newly appending the channel that SV light uses for transmitted in both directions SV light, main signal light and SV light wavelength are also set above-mentioned wavelength usually for, so, still have the power that can't prevent between the main signal light of transmission in the same way and the SV light power transfer that produces and SV light and reduce the many problems of quantitative change.In addition, the also not open SV light wavelength of how selecting in patent documentation 3.
Summary of the invention
The present invention foundes in view of above problem just, its purpose is, have special-purpose monitor optical wavelength and the monitor optical wavelength that can select transmission loss to try one's best little, and, can reduce because Raman scattering phenomenon and the power of the monitor optical robbed by main signal light realizes that the relaying length of an interval is apart from change as far as possible.
In order to reach above-mentioned purpose, the invention provides the monitor optical transmission method in a kind of wave division multiplexing transmission system, it is the light transmission path of wavelength division multiplexed light that this wave division multiplexing transmission system has transmission main signal light, it is characterized in that, to the rightabout transmitting, monitoring light of the transmission direction of this main signal light, this monitor optical has the wavelength that can produce Raman gain at the wave band of this main signal light owing to the Raman scattering phenomenon in this light transmission path.
And this monitor optical can have the wavelength of short wavelength side of the wave band of this main signal light, and the wave band of this main signal light can be C-band or C-band and L-band.
And then, also can be at the receiver side of this monitor optical, monitor the power of this monitor optical, the result of this supervision is when detecting this light transmission path unusual, stop to send this main signal light to this light transmission path, perhaps, will be reduced to predetermined light level to the transmission level that this light transmission path sends this main signal light.
And, Wavelength division multiplexing transmission apparatus of the present invention and transmission main signal light are that the light transmission path of wavelength division multiplexed light is connected and constitutes wave division multiplexing transmission system, it is characterized in that, this Wavelength division multiplexing transmission apparatus has: receiving element, and it is received in this main signal light that transmission comes in this light transmission path; The monitor optical generation unit, it generates monitor optical, and this monitor optical has the wavelength that can produce Raman gain at the wave band of this main signal light owing to the Raman scattering phenomenon; And the monitor optical coupling unit, the monitor optical that it is generated by this monitor optical generation unit to this light transmission path coupling at the rightabout of this main signal light is also transmitted.
And, Wavelength division multiplexing transmission apparatus of the present invention and transmission main signal light are that the light transmission path of wavelength division multiplexed light is connected and constitutes wave division multiplexing transmission system, it is characterized in that this Wavelength division multiplexing transmission apparatus has: transmitting element, it sends this main signal light to this light transmission path; The monitor optical separative element, it is monitoring of separation light from this light transmission path, this monitor optical has can be at the wave band of this main signal light owing to the Raman scattering phenomenon produces the wavelength of Raman gain, and the rightabout transmission from this main signal light comes in this light transmission path; And the monitor optical receiving element, it receives the monitor optical of being separated by this monitor optical separative element.
And then, this monitor optical receiving element also can have: monitoring unit, it monitors the power of this monitor optical, and control part, its supervision result in this monitoring unit when detecting this light transmission path unusual, stops this transmitting element and sends this main signal light to this light transmission path, perhaps, this transmitting element is reduced to predetermined light level to the transmission level that this light transmission path sends this main signal light, and this monitor optical can have the wavelength of short wavelength side of the wave band of this main signal light.
And the wave band of this main signal light can be C-band or C-band and L-band.
According to the invention described above, because in light transmission path to the rightabout transmitting, monitoring light of the transmission direction of main signal light, this monitor optical has the wavelength that can produce Raman gain at the wave band of main signal light owing to the Raman scattering phenomenon, so, high-power zone at main signal light, for example near the transmitter side of main signal light, the power of monitor optical is owing to the transmission loss of light transmission path reduces, on the contrary, at the power of main signal light owing to the transmission loss of light transmission path reduces to a certain degree zone, be near the receiver side of main signal light, become the very big state of power of monitor optical.Therefore, with in light transmission path, compare to the situation of same direction transmission main signal light and monitor optical, near the transmitter side of main signal light, monitor optical is few to the power transfer quantitative change of main signal light, the degree of decay that can suppress the monitor optical that the Raman scattering phenomenon causes, its result has solved the problem of the link budget of monitor optical, can realize that the relaying length of an interval is apart from change.
And, because rightabout transmitting, monitoring light to main signal light, so, transmitter side at main signal light, can't normally receive monitor optical and when detecting light transmission path unusual, can carry out opening circuit or transmission power control of main signal light immediately, so, can shorten the reply time that produces when unusual, improve fail safe.
Description of drawings
Fig. 1 is the block diagram of the structure of wavelength division multiplexing (WDM) transmission system that an embodiment of the invention are shown.
Fig. 2 is a block diagram of simplifying the WDM transmission system that an embodiment of the invention are shown.
Fig. 3 is the figure of an example that the power delivery range performance of the main signal light of WDM transmission system of an embodiment of the invention and SV light is shown.
Fig. 4 is the figure of an example that the power spectrum of main signal light in each tandem office of WDM transmission system of an embodiment of the invention and SV light schematically is shown.
Fig. 5 is the figure of an example of analog result that the WDM transmission system of an embodiment of the invention is shown.
Fig. 6 is the block diagram of the control of opening circuit that is used to illustrate the WDM transmission system of an embodiment of the invention.
Fig. 7 is the block diagram that the structure of existing WDM transmission system is shown.
Fig. 8 is the figure that the wavelength characteristic example of Raman scattering phenomenon schematically is shown.
Fig. 9 is used for illustrating the figure that significantly produces the position of Raman scattering phenomenon in existing WDM transmission system.
Figure 10 is the figure that the power delivery range performance of main signal light in the existing WDM transmission system and SV light is shown.
Figure 11 is the figure that the power spectrum before and after the transmission of main signal light in the existing WDM transmission system and SV light is shown.
Figure 12 is the figure that the wavelength characteristic of the transmission loss in the general optical fiber is shown.
Label declaration
1c, 1d, 1e: tandem office's (Wavelength division multiplexing transmission apparatus)
2a, 2b: image intensifer
The 3:SV optical receiver
4a, 4b:SV light partial wave coupler
5a, 5b: transmission optical fiber
The 6:SV optical transmitter
The photosynthetic ripple coupler of 7a, 7b:SV
8a, 8b:E/O transducer
9a, 9b: handling part
10a, 10b:O/E transducer
11: unit controls portion
12a, 12b: power monitor portion
Embodiment
Below, with reference to description of drawings an embodiment of the invention.
Fig. 1 is the block diagram of the structure of wavelength division multiplexing (WDM) transmission system that an embodiment of the invention are shown.
As shown in Figure 1, this WDM transmission system constitutes to be had: as a plurality of 1c of tandem office of wavelength division multiplexing (WDM) transmitting device, 1d, 1e ... (tandem office beyond 1c, 1d, the 1e omits diagram, below, be designated as " tandem office 1 " in the situation following table of not distinguishing them); And be connected for the office that can continue in these carries out bidirectional optical between 1 light transmission path (optical fiber) 5a of up (the paper right of Fig. 1) usefulness between each tandem office 1 and light transmission path (optical fiber) 5b of descending (the paper left of Fig. 1 to) usefulness (below, sometimes souvenir for transmission with optical fiber 5a, 5b).
And then each tandem office 1 constitutes respectively to have: image intensifer 2a, 2b; SV light partial wave coupler 4a, 4b; The photosynthetic ripple of SV coupler 7a, 7b; Electricity/light (E/O) transducer 8a, 8b; Handling part 9a, 9b; Light/electricity (O/E) transducer 10a, 10b; And unit controls portion 11.In addition, below, when not needing to distinguish image intensifer 2a, 2b, recording and narrating sometimes is image intensifer 2.And other structural elements are recorded and narrated too sometimes.
Here, in each tandem office 1, image intensifer 2a is respectively applied for and is amplified in the up main signal light of propagating in this WDM transmission system, and image intensifer 2b is respectively applied for and amplifies descending main signal light, and they can use for example EDFA or raman amplifier etc.These image intensifers 2a, 2b are subjected to the control from unit controls described later portion 11, can start, gain controlling, action such as open circuit.
And, SV light partial wave has as the function of transmission with the monitor optical separative element of optical fiber 5b with coupler 4a, be used for the SV light that comes from the transmission of the rightabout (up direction) of descending main signal light with optical fiber 5b in transmission is carried out partial wave and taking-up, and, have function concurrently as the transmitting element of the descending main signal light after tandem office's 1 transmission of side is amplified by image intensifer 2b downstream with optical fiber 5b via transmission.
Equally, SV light partial wave has as the function of transmission with the monitor optical separative element of optical fiber 5a with coupler 4b, be used for the SV light that comes from the transmission of the rightabout (down direction) of up main signal light with optical fiber 5a in transmission is carried out partial wave and taking-up, and, have function concurrently as the transmitting element of the up main signal light after upstream tandem office's 1 transmission of side is amplified by image intensifer 2a with optical fiber 5a via transmission.
And then, the photosynthetic ripple of SV has as the function of transmission with the monitor optical coupling unit of optical fiber 5a with coupler 7a, be used for to the up transmission SV light of optical fiber 5a coupling from the descending usefulness of E/O transducer 8a, the rightabout of the main signal light that transmission comes in transmitting with optical fiber 5a transmits this SV light.That is, the photosynthetic ripple of SV has concurrently as being received in the function of transmission with the receiving element of the next up main signal light of transmission among the optical fiber 5a with image intensifer 2a with coupler 7a.
Equally, the photosynthetic ripple of SV has as the function of transmission with the monitor optical coupling unit of optical fiber 5b with coupler 7b, be used for to the descending transmission SV light of optical fiber 5b coupling from the up usefulness of E/O transducer 8b, the rightabout of the main signal light that transmission comes in transmitting with optical fiber 5b transmits this SV light.That is, the photosynthetic ripple of SV has concurrently as being received in the function of transmission with the receiving element of the next descending main signal light of transmission among the optical fiber 5b with image intensifer 2b with coupler 7b.
E/O transducer 8a brings into play function as the monitor optical generation unit with unit controls portion 11 and handling part 9a, to be light signal (SV light) and output to the photosynthetic ripple of SV coupler 7a from the SV conversion of signals of handling part 9a as the descending usefulness of the signal of telecommunication, E/O transducer 8b brings into play function as the monitor optical generation unit with unit controls portion 11 and handling part 9b, will be light signal (SV light) and output to the photosynthetic ripple of SV coupler 7b from the SV conversion of signals as the up usefulness of the signal of telecommunication of handling part 9b.In addition, these E/ O transducers 8a, 8b use for example formation such as laser diode.
And, O/E transducer 10a brings into play function as the monitor optical receiving element with handling part 9a and unit controls portion 11, to import light (here for by the up SV light of SV light partial wave after with coupler 4a partial wave) is converted to the signal of telecommunication and outputs to handling part 9a, equally, O/E transducer 10b will import light (here for by the descending SV light of SV light partial wave after with coupler 4b partial wave) and be converted to the signal of telecommunication and output to handling part 9b.These O/ E transducers 10a, 10b use for example formation such as photodiode.
And then, handling part 9a has following function: promptly, to be transferred to unit controls portion 11 from the up SV signal of the reception of O/E transducer 10a as the signal of telecommunication, on the other hand, acceptance is from the indication of unit controls portion 11, generate necessary descending SV signal and also be transferred to E/O transducer 8a, can also be suitable for the mutual format conversion etc. of the transmitting-receiving of the SV signal between these O/E transducers 10a, E/O transducer 8a and the unit controls portion 11.
Equally, handling part 9b has following function: promptly, to be transferred to unit controls portion 11 from the descending SV signal of the reception of O/E transducer 10b as the signal of telecommunication, on the other hand, acceptance is from the indication of unit controls portion 11, generate necessary up SV signal and also be transferred to E/O transducer 8b, can also be suitable for the mutual format conversion etc. of the transmitting-receiving of the SV signal between these O/E transducers 10b, E/O transducer 8b and the unit controls portion 11.
Promptly, as the monitor optical generation unit performance function that generates up SV light, O/E transducer 10a (10b) uses the monitor optical receiving element of the descending SV light behind coupler 4 partial waves to bring into play function with handling part 9b (9a) and unit controls portion 11 as receiving by SV light partial wave to E/O transducer 8a (8b) with handling part 9a (9b) and unit controls portion 11.
And, unit controls portion 11 carries out the integral body control of tandem office 1, can be according to the SV signal that receives from above-mentioned handling part 9a, 9b, send the control signal that is used for control unit (being image intensifer 2 here) to the unit, perhaps, the 9a of control and treatment portion, 9b are to generate the SV signal that be transferred to upstream or downstream.
In addition, the prerequisite of the wave band of the main signal light of native system is, as described by Figure 12, consider in the easiness that fiber loss is suppressed increase the transmission amount of information and amplify simultaneously, use C-band (1530nm～1565nm) or C-band and L-band (these both sides of 1565nm～1625nm) for minimal.And,,, select the short wavelength side (short wavelength side of C-band) of the wave band of main signal light, near the wavelength for example 1510nm in order to make the fiber loss minimum about the SV light wavelength.Under this situation, as described by Fig. 8, at the wave band of main signal light owing to the Raman scattering phenomenon produces Raman gain.In other words, this routine SV light has the wavelength that produces Raman gain at the wave band of main signal light owing to the Raman scattering phenomenon.
Below, the action of the WDM transmission system of the present embodiment that constitutes as mentioned above is described.
At first, to transmit main signal light with identical in the past method.Promptly, at main signal light up direction, the main signal light that sends from forwarding office (omitting diagram) is input to image intensifer 2a via the photosynthetic ripple of the SV of the 1c of tandem office with coupler 7a, after image intensifer 2a amplifies, sends to transmission optical fiber 5a via SV light partial wave with coupler 4b.Carry out this transmission repeatedly, thus, main signal light is finally received by office of acceptance's (omitting diagram) successively via the 1d of tandem office, transmission optical fiber 5a, the 1e of tandem office.
Equally, at main signal light down direction, the main signal light that sends from forwarding office is input to image intensifer 2b via the photosynthetic ripple of the SV of the 1e of tandem office with coupler 7b, after image intensifer 2b amplifies, send to transmission optical fiber 5b via SV light partial wave with coupler 4a, via the 1d of tandem office, transmission optical fiber 5b, the 1c of tandem office, finally receive successively by office of acceptance.
Relative therewith, in the present embodiment, SV light transmits with the rightabout to main signal light in the optical fiber 5 in the transmission that main signal light transmits.That is, as mentioned above, send the main signal light time to up direction, SV light identical transmission with optical fiber 5 in to the rightabout of the transmission direction of main signal light, be that down direction transmits.For example, receive the 1e of tandem office of up main signal light with optical fiber 5a via transmission from the 1d of tandem office, utilize the photosynthetic ripple of SV with coupler 7a identical transmission with optical fiber 5a in the descending SV light of coupling, thus, at the rightabout of main signal light towards the 1d of tandem office transmission SV light.
In the 1d of tandem office, utilize SV light partial wave the above-mentioned descending SV light that transmission in transmitting with optical fiber 5a to be carried out partial wave, be input to O/E transducer 10b, in O/E transducer 10b with coupler 4b, light/electricity is converted to the SV signal as the signal of telecommunication, is transferred to handling part 9b.
And then the SV signal is transferred to unit controls portion 11, and when this SV signal mail to the 1d of this tandem office, unit controls portion 11 was according to the content of this SV signal, and performance element is controlled (transmission power control of image intensifer 2a, 2b etc.).In addition, can discern the SV signal by the node identifying information of in the SV signal, setting and whether mail to the 1d of this tandem office.And, receiving the SV signal is not to mail under the situation of the 1d of this tandem office, unit controls portion 11 does not handle especially to the 1d of this tandem office, but, when mailing to other tandem offices 1 (for example 1c of tandem office), by handling part 9a, E/O transducer 8a and the photosynthetic ripple of the SV coupler 7a of opposite side, be transferred to the 1c of tandem office of hypomere (downstream) with optical fiber 5a via transmission.
At this moment, in handling part 9a, 9b, situation according to transmitting device (being transmitting device and transmission path) is upgraded the SV signal, then, send to the SV light of transmission by the photosynthetic ripple of SV with coupler 7a, in the 1c of tandem office with optical fiber 5a, with action among the above-mentioned 1d of tandem office similarly, utilize SV light partial wave with coupler 4b partial wave, be transferred to unit controls portion 11, carry out the processing of passing on of necessary unit controls, SV light according to this reception SV signal via O/E transducer 10b and handling part 9b.In addition, the transmission of the SV light of up direction is also similarly carried out with above-mentioned down direction.
As mentioned above, by transmission SV light between tandem office 1, can carry out the condition monitoring between each tandem office 1, perhaps, the information of tandem office 1 of upstream side (or downstream) is passed on by the tandem office of side (or upstream side) downstream, according to these information, can make said units control optimization.
Then, use the influence of the Raman scattering phenomenon of Fig. 2～5 explanation present embodiments.
Fig. 2 is a block diagram of simplifying the WDM transmission system that present embodiment is shown, and the structure of a direction between a relay area that is conceived to above-mentioned WDM transmission system is shown.In this Fig. 2, marked the structure of the label identical with described label, unless otherwise specified, be exactly the structure identical or the same with described structure.And, SV optical receiver 3 is equivalent to the piece by O/E transducer 10b among Fig. 1 and handling part 9b (or O/E transducer 10a and handling part 9a) formation, and SV optical transmitter 6 is equivalent to the piece by handling part 9a among Fig. 1 and E/O transducer 8a (or handling part 9b and E/O transducer 8b) formation equally.
In this Fig. 2, at first, as mentioned above, main signal light is transferred to tandem office 1d (or 1e) via transmission with optical fiber 5a (or 5b) from the 1c of tandem office (or 1d).Relative therewith, the SV optical transmitter 6 that SV light passes through the 1d of tandem office (or 1e) sends, and the rightabout to main signal light in transmitting with optical fiber 5a (or 5b) transmits, by SV optical receiver 3 receptions of the 1c of tandem office (or 1d).
Fig. 3 illustrates an example of the transmission range characteristic of the main signal light of this moment and the power of SV light.
By this Fig. 3 as can be known, transmitter side at main signal light is among the 1c of tandem office (or 1d), the power of main signal light (channel mean) is before being subjected to the transmission loss of transmission with optical fiber 5a (or 5b), so it is maximum, relative therewith, the power of SV light has been subjected to the transmission loss of transmission with optical fiber 5a (or 5b), so minimum.
Relative therewith, be among the 1d of tandem office (or 1e) at the receiver side of main signal light, the power of main signal light has been subjected to the transmission loss of transmission with optical fiber 5a (or 5b), so it is minimum, on the contrary, the power of SV light is before being subjected to the transmission loss of transmission with optical fiber 5a (or 5b), so maximum.
That is, this be because, main signal light and SV light respectively in identical transmission with transmission in the optical fiber 5, they are subjected to transmitting the decay comparably with the transmission loss of optical fiber 5.
And, in the case of this example, the Raman scattering phenomenon is a non-linear phenomena, so, such shown in the label among Fig. 3 102, the forwarding office (office of acceptance of main signal light) that mainly is created in the bigger SV light of the power of SV light is near the 1d of tandem office (or 1e), but, near the 1d of this tandem office (or 1e), diminish as the power of the main signal light that is exaggerated light, so it is little that the amplification effect of Raman scattering phenomenon (transmits the situation of main signal light and SV light) in the same way also than in the past.That is, based on the SV light of Raman scattering phenomenon to the power transfer of main signal light also than lacked in the past, can suppress decay based on the SV light of Raman scattering phenomenon.
Here, Fig. 4 schematically illustrates an example of the power spectrum of each flashlight among 1c of tandem office (or 1d) and the 1d of tandem office (or 1e).The left side of Fig. 4 illustrates the 1c of tandem office (or 1d) (forwarding office of main signal light, the office of acceptance of SV light) the main signal light in and the power spectrum of SV light, the right side of Fig. 4 illustrates the main signal light among the opposed 1d of tandem office (or 1e) (office of acceptance of main signal light, the forwarding office of SV light) and the power spectrum of SV light.
Promptly, the left side of Fig. 4 is illustrated in the received power of the SV light that the 1c of tandem office (or 1d) receives and the transmitted power of the main signal light that sends from the 1c of this tandem office (or 1d), and the right side of Fig. 4 illustrates the transmitted power of the SV light that sends from the 1d of tandem office (or 1e) and the received power of the main signal light that receives in this tandem office 1d (or 1e).
By this Fig. 4 as can be known, (with reference to Figure 11) compares with existing power spectrum, and the Raman scattering phenomenon is little to the amplification effect of main signal light,, can suppress the power transfer amount of SV light to main signal light, the power attenuation that can alleviate SV light that is.
Use analog result shown in Figure 5 that this situation is described.In addition, in this simulation, use DSF (Dispersion Shifted Fiber: dispersion shifted optical fiber) as transmission optical fiber 5, about main signal light, if wave band is a C-band, channel quantity (wavelength division multiplexing quantity) is 40, sends output level to be+3dBm, and, about SV light, if wavelength is 1510nm, sending output level is+6dBm to calculate.And then the distance between the tandem office 1 herein is 120km (loss to the flashlight of wavelength 1550nm is 24dB).
So, by this Fig. 5 as can be known, as in the past, transmitting with transmitting under the situation of main signal light and SV light to same direction in the optical fiber 5, shown in solid line 103, in transmitting terminal, main signal light and SV light both sides' power height, so, at (about 0～20km) near the transmitting terminal, the power of SV light is robbed and big high attenuation by the wide amount of main signal, after transmission 120km, compare with the situation (only being subjected to the situation of transmission loss :) of the influence that is not subjected to the Raman scattering phenomenon with reference to dotted line 104, SV light reduces about 1.7dB, relative therewith, under the situation of the transmission method that uses present embodiment, that is, transmit round about under the situation of main signal light and SV light, shown in label 105 in optical fiber 5 in identical transmission, receiving terminal at the main signal light of the transmitted power maximum of SV light, the power of main signal light reduces, so, littler than in the past based on the SV luminous power of Raman scattering phenomenon to the transfer amount of main signal light, even after the transmission 120km, compare with the situation (with reference to dotted line 106) of the influence that is not subjected to the Raman scattering phenomenon, the reduction amount only is that the attenuation of SV light has been improved about 0.7dB about 1.0dB.
Therefore, according to as the monitor optical transmission method in the wave division multiplexing transmission system of the 1st execution mode of the present invention, can suppress the decay of the SV light that Raman scattering causes, so, can realize the long Distance Transmissionization of SV light, solved the problem of the link budget of SV light, can realize that the relaying length of an interval is apart from change.That is, can cut down the needed tandem office of WDM transmission system quantity, make huge contribution to reducing cost.
But, as mentioned above, transmit round about under the situation of main signal light and SV light in optical fiber 5 in same transmission, be the control in the tandem office 1 with in the past difference based on SV light.Promptly, successively under the situation of SV light is passed on by each tandem office 1, the transmission of only transmitting SV light is with optical fiber and different (switch up/descending) in the past, other controls are with identical in the past, but, need change to following control: promptly, by the transmission that produces obstacle to transmitter side with existing receiver side from SV light with optical fiber 5 different, to the transmission of transmitter side transmission main signal light with sending (feedback) SV light the optical fiber 5, opening circuit when producing transmission with obstacles such as optical fiber 5 broken strings controlled etc.
For example, under the situation of control that opens circuit, in the past, when in transmission usefulness optical fiber, producing broken string, in forwarding office, monitor the power of main signal reflection of light back light (from the reverberation of broken string position), when the power that detects this reflection back light surpasses a certain threshold value, the light transmission of forwarding office is opened circuit.But, in the method, can't open circuit or the wrong diagnosis road owing to reflect the power of back light sometimes.And as other control methods, also have following method: promptly, when producing broken string in the optical fiber, detect the situation that can't receive SV light in office of acceptance in transmission, additional this meaning and to the forwarding office feedback in the SV signal makes the light of forwarding office send thus and opens circuit.But, when opening circuit, need feed back SV light to forwarding office, so, the light transmission of forwarding office is opened circuit.
Therefore, with reference to Fig. 6 the control of opening circuit in this routine WDM transmission system is described.As shown in Figure 6, in the 1c of tandem office, 1d, the difference secondary power monitor 12a of portion, 12b.The 12a of these power monitor portions, 12b have the function as the monitoring unit of SV signal, for example, monitor that O/ E transducer 10a, 10b carry out the received power of the SV signal after light/electricity is changed, the interruption of transmitting thus with optical fiber 5a, 5b detects, carrying out under the situation of interrupting detecting, pass on this meaning via handling part 9a, 9b to unit controls portion 11, thus, can carry out the control (transmission power control) of opening circuit of image intensifer 2a, 2b.
In addition, the power-monitoring of SV light also can be at light level, be that the light that O/ E transducer 10a, 10b carry out before the conversion of light/electricity carries out.And Fig. 6 only illustrates between relay area between 1c of tandem office and the 1d of tandem office, still, between other relay area too.And then, in this Fig. 6, marked the structure of the label identical with described label, unless otherwise specified, be exactly the structure identical or the same with described label.
At first, as shown in Figure 6, suppose to have produced broken string in optical fiber 5a in the transmission of transmitting up main signal light (descending SV light).Under this situation, forwarding office at main signal light is among the SV light partial wave usefulness coupler 4b of the 1c of tandem office, do not receive before producing broken string at the transmission descending SV light of propagating to the rightabout of main signal light among the optical fiber 5a, so, in the 12b of power monitor portion of the 1c of tandem office, detect output interruption (interruption in power) from the SV signal of O/E transducer 10b.
So, the 12b of power monitor portion passes on the signal of notifying this meaning (line interruption) via handling part 9b to unit controls portion 11, thus, (image intensifer 2a or image intensifer 2a, 2b both sides) open circuit control [perhaps to 11 pairs of unit of unit controls portion, to be reduced to predetermined (safety) light level with the transmission level that optical fiber 5a sends main signal light to the transmission behind the broken string], thus, make the 1c of tandem office to transmission with the transmission of the light of optical fiber 5a open circuit (stop or power is reduced to safe level).Thus, can prevent to radiate high-power light from the broken string position.
In addition, during with optical fiber 5b broken string, the forwarding office that utilizes descending main signal light is that the 12a of power monitor portion of the 1d of tandem office interrupts detecting in opposed transmission, at least to the image intensifer 2b control (transmission power control) of opening circuit.
Like this, in the WDM of present embodiment transmission system, transmit SV light in transmission with the rightabout to main signal light in the optical fiber 5, so, forwarding office at main signal light is in the tandem office 1, can't normally receive SV light, thus, can detect transmission unusual with optical fiber 5, because still be OFF (power that the has or not SV light) control of opening circuit by SV light ON, so can suppress misoperation, and then, because can be immediately (unlike in the past, feed back the detection information of interrupting) by SV light carry out opening circuit or transmission power control of main signal light at the forwarding office 1 of main signal light, so, can shorten the reply time that produces when unusual, improve fail safe.
In addition, the invention is not restricted to above-mentioned execution mode, in the scope that does not break away from purport of the present invention, certainly carry out various distortion and implement.
Claims (9)
1. the monitor optical transmission method in the wave division multiplexing transmission system, it is the light transmission path of wavelength division multiplexed light that this wave division multiplexing transmission system has transmission main signal light, it is characterized in that,
To the rightabout transmitting, monitoring light of the transmission direction of this main signal light, this monitor optical has the wavelength that can produce Raman gain at the wave band of this main signal light owing to the Raman scattering phenomenon in this light transmission path.
2. the monitor optical transmission method in the wave division multiplexing transmission system according to claim 1 is characterized in that,
This monitor optical has the wavelength of short wavelength side of the wave band of this main signal light.
3. the monitor optical transmission method in the wave division multiplexing transmission system according to claim 2 is characterized in that,
The wave band of this main signal light is C-band or C-band and L-band.
4. according to the monitor optical transmission method in each the described wave division multiplexing transmission system in the claim 1～3, it is characterized in that,
At the receiver side of this monitor optical,
Monitor the power of this monitor optical,
The result of this supervision when detecting this light transmission path unusual, stops to send this main signal light to this light transmission path, perhaps, will be reduced to predetermined light level to the transmission level that this light transmission path sends this main signal light.
5. Wavelength division multiplexing transmission apparatus, this transmitting device and transmission main signal light are that the light transmission path of wavelength division multiplexed light is connected and constitutes wave division multiplexing transmission system, it is characterized in that this Wavelength division multiplexing transmission apparatus has:
Receiving element, it is received in this main signal light that transmission comes in this light transmission path;
The monitor optical generation unit, it generates monitor optical, and this monitor optical has the wavelength that can produce Raman gain at the wave band of this main signal light owing to the Raman scattering phenomenon; And
The monitor optical coupling unit, the monitor optical that it is generated by this monitor optical generation unit to this light transmission path coupling at the rightabout of this main signal light is also transmitted.
6. Wavelength division multiplexing transmission apparatus, this transmitting device and transmission main signal light are that the light transmission path of wavelength division multiplexed light is connected and constitutes wave division multiplexing transmission system, it is characterized in that this Wavelength division multiplexing transmission apparatus has:
Transmitting element, it sends this main signal light to this light transmission path;
The monitor optical separative element, it is monitoring of separation light from this light transmission path, this monitor optical has can be at the wave band of this main signal light owing to the Raman scattering phenomenon produces the wavelength of Raman gain, and the rightabout transmission from this main signal light comes in this light transmission path; And
The monitor optical receiving element, it receives the monitor optical of being separated by this monitor optical separative element.
7. Wavelength division multiplexing transmission apparatus according to claim 6 is characterized in that,
This monitor optical receiving element has:
Monitoring unit, it monitors the power of this monitor optical; And
Control part, its supervision result in this monitoring unit is when detecting this light transmission path unusual, stop this transmitting element and send this main signal light, perhaps, this transmitting element is reduced to predetermined light level to the transmission level that this light transmission path sends this main signal light to this light transmission path.
8. according to each the described Wavelength division multiplexing transmission apparatus in the claim 5～7, it is characterized in that,
This monitor optical has the wavelength of short wavelength side of the wave band of this main signal light.
9. Wavelength division multiplexing transmission apparatus according to claim 8 is characterized in that,
The wave band of this main signal light is C-band or C-band and L-band.
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