JP2002504777A - Dense wavelength division multiplexing method and system in 1310 nm band - Google Patents

Abstract

(57) Abstract Dense wavelength division multiplexing within the 1310 nm band is achieved on single mode fiber. The carrier wavelength is selected from within two regions: a low subband (140) and a high subband (160) on either side of the guard band (120). The guard band has a zero-dispersion wavelength λ ₀ of the monomodal fiber in the optical communication link and separates the low and high sub-bands within the 1310 nm band. Dispersion compensation is provided for the carrier signal in each dense WDM channel in the low and high subbands.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to fiber optic networks and multi-channel communication systems.

[0002]

[Prior art]

Modern communication systems increasingly rely on fiber optic networks to carry an increasing amount of data between sites. The use of multiple optical carriers (also called channels) on the same optical fiber increases capacity. Wavelength division multiplexing (WDM) allows multiple channels to be carried on fiber at various carrier wavelengths. Attenuation and dispersion in an optical fiber limits the distance an optical signal can travel without amplification and / or dispersion compensation.

In commercially available optical fibers, there are two infrared wavelength regions or bands where the fiber material exhibits minimal attenuation. One region is generally referred to as the "1310 nm (nanometer) region" and has a wavelength band of about 1120-1385 nm with a minimum loss of about 0.4 dB / km (decibel / km). The other region has a longer wavelength band in the range of about 1500-1600 nm,
And it has a minimum attenuation of about 0.2 dB / km. The region between 1520 and 1560 nm is often amplified by erbium-doped material and is thus referred to as the “erbium band” or “erbium region”.

[0004] Due to the low loss and corresponding reduction in required line amplication, the telecommunications industry has found that the telecommunications industry, particularly in multi-channel and WDM applications, has one problem.
Attention has been focused on devices and fibers that support operation around 550 nm. In the 1310 nm band, new fibers, semiconductor lasers and receivers
As it was developed to support WDM operation at 0 nm, it was essentially obsolete. Until now, off-the-shelf systems have mainly used 13 channels for single channel communication.
A 10 nm region has been used.

[0005] To increase the use of optical communication fibers, wavelength division multiplexing (WDM) is used to transmit multiple optical carriers along a fiber, each at a different wavelength. Engineers put as many wavelengths as possible into a single fiber,
Efforts are made to maximize the capacity of the erbium band in communication networks. While two- or four-wavelength systems are fairly common, the telecommunications industry has established that in narrow erbium bands, 8 or 16 at 100 GHz or 50 GHz intervals.
You are planning how to pack your channel. This includes transmitter stability, receiver selectivity, ease of line amplification and equalization, and four-wave mixing.
ng: FWM) represents a significant challenge in avoiding non-linear interference effects. Therefore, only a few WDM channels,
In the erbium band of fiber optic networks, it cannot be supported efficiently without sacrificing reliable, high-quality communications.

For example, according to one International Telecommunication Union (ITU) standard, 100 gigahertz (GHz) spacing is provided between channels to maintain signal separation and quality. This 100 GHz spacing translates into a wavelength range of about 0.8 nm, meaning that only 40 WDM channels can fit within one erbium band. However, if each optical carrier is modulated at a high data bit rate, such as 10 Gbit / s (Gb / s), a 200 GHz spacing is preferably used between channels to prevent crosstalk. As a result, 2
Only 16 channels with 00 GHz spacing can be used efficiently in the operating range within the erbium band of about 1530-1561 nm.

Further, group velocity dispersion complicates WDM placement in the erbium band. The reason is that a given fiber is slanted (sl
oped) to show the dispersion characteristics as a function of wavelength. Therefore, the fiber
Only on a subset of the wavelengths valid in the erbium band small dispersion values can be shown. For a distance of the carrier wavelength from the zero dispersion wavelength (λ ₀ ), the dispersion effect needs to be compensated for somewhere along the fiber to ensure reliable signal reception. This further limits the number of channels that can be used in the erbium band for reliable high quality communication.

[0008] One of the earliest forms of single-mode fiber that has been widely used has in the past been known as Non-Dispersion Shifted Fiber (ND).
SF). For example, such a fiber has a zero dispersion wavelength (λ ₀ ) around 1312 nm and a zero dispersion slope S ₀ of about 0.090 ps / nm ² -km. For example, CORNING (R) SMF-28 ^TM CPC6 single-mode optical f
See iber, Product Information, 1997, pages 1 and 3. In addition, NDSF fibers may have a positive average dispersion over the erbium band. In practice, designers have been able to compensate for this by placing negative-slope fibers in places on the optical link.

A more recent fiber, Dispersion Shifted Fib
er: DSF) is formulated such that λ ₀ is 1550 nm, which makes it ideal for transmission at this wavelength. The drawback, however, is that if several WDM carriers are packed around this wavelength and launched into a common fiber with sufficient optical power density, the carriers will be subject to four-wave mixing (FWM) due to the nonlinearity of the fiber material. ).

[0010] The capacity of fiber and fiber networks needs to increase. Multiple channels need to be added without sacrificing the reliability and quality of voice and data communications. The entire band of monomodal fiber, such as NDSF fiber and / or DSF fiber, needs to be optimized. There is a need for a dense WDM window that can use multiple channels to support multi-channel communication over a single mode fiber.

[0011]

Problems to be Solved by the Invention and Means for Solving the Problems

The present invention provides a method and system for dense wavelength division multiplexing (WDM) that supports multi-channel communication in the 1310 nm band over a fiber link. In one example, high-density WDM supports multi-channel communication in the 1310 nm band on single mode fiber. Thus, according to the present invention,
A greater number of channels can be added within the 1310 nm region, which is relatively wider than the erbium band, which increases the capacity of monomodal optical fibers in a fiber optic network. This eliminates the need for more expensive options to increase the capacity of the fiber optic network, such as placing additional fibers in the network or adding channels to the crowded erbium band.

[0012] The present invention provides that a single mode fiber link can be used instead of the erbium band or
In addition, it provides a multi-channel optical communication link that carries high-density WDM optical signals within the 1310 nm band. Specifically, the carrier wavelength is determined by the protection frequency band (
guardband) on both sides (low subband and high subband). Guard band encompasses a zero dispersion wavelength lambda _0, the zero dispersion wavelength lambda ₀ is for a large number of arranged fibers and new single style fiber in an optical fiber network, is about 1312 ± 3 nm .

[0013] The width of the guard frequency band can be set to minimize four-wave mixing (FWM). In one embodiment of the invention, the guard band around λ _{0 is such} that the absolute value of the variance in both the low and high subbands is approximately equal to 0.5 ps / nm-km, or , Having a greater width. In another embodiment, a guard band around 17 nm centered at λ ₀ is used to separate the low and high sub-bands. In each of these embodiments, the width of the guard band is such that closely spaced carriers co-propagate in a dispersive environment.
Avoids four-wave mixing (FWM) by ensuring that
It "washes out" the phase coherence required for efficient mixing over the length of the fiber. Thus, the density of the modulated carrier can occupy the lower and / or higher subbands without causing significant interference. The presence of guard bands is particularly important for reducing FWM on non-dispersion shifted fibers where the magnitude of the dispersion is not as great as in dispersion shifted fibers.

By straddling the zero dispersion wavelength λ ₀ , the two subbands or regions can further know different dispersion values. For NDSF, the lower subband or shorter wavelength region knows negative dispersion, and the higher subband or longer wavelength region knows positive dispersion. Positive dispersion in the high subband can be easily compensated for using conventional DSF or recently introduced LS fiber. The reason is that they are optimized for 1550 nm and 1310
This is because it has a substantially negative dispersion in the nm band. In addition, positive dispersion in the high sub-band is corrected and improved by a chirped fiber Bragg grating set to carry negative dispersion, as is known in the prior art. be able to. Similarly, regions of lower sub-bands or shorter wavelengths can be compensated for negative dispersion by a chirped fiber Bragg grating set to carry positive dispersion.

[0015] For DSF, both the low and high subbands know a negative variance. Thus, such negative dispersion in the low and high sub-bands is due to the chirped fiber Bragg grating set to carry positive dispersion.
Can compensate. In addition, single mode fibers (NDSF and DSF) introduce positive slope dispersion over the 1310 nm region in both the low and high subbands. Such a positive dispersion slope can be corrected and improved with a chirped fiber Bragg grating, as is known in the prior art.

The 1310 nm band is relatively wide, and the absorption peaks of silica and water (absorpti)
on peak) sets the limit on the long end. In addition, there is a minimum wavelength limit imposed by the geometry of the fiber to ensure single mode propagation. In one example, the present invention relates to
It provides low and high subbands ranging from 0 nm and 1320-1365 nm, which allow for a much larger number of channels than would be expected for a common but narrow erbium band.

In one embodiment of the present invention, a multi-channel optical communication system and method are provided. Multi-channel optical communication systems and methods require multiple carrier signals transmitted over a single mode fiber. Monomodal fibers have a zero dispersion wavelength λ ₀ . The carrier signal has a wavelength in at least one of the low subband and the high subband in the 1310 nm band. The low and high subbands are separated by a guard band that includes the zero dispersion wavelength λ ₀ of the monomodal fiber. In a preferred example, the zero-dispersion wavelength λ ₀ is in the range of about 1309-1315 nm. According to a further feature, the guard band has a width of at least 2 nm, preferably 17 nm.

In a preferred example, the guard band has a range of about 1300 to 1320 nm. The low sub-band has a range of about 1270-1300 nm and the high sub-band has a range of about 1320-1365 nm. A plurality of carrier signals carry data in respective high-density WDM channels within the low and high subbands. The high-density WDM channel is at least about 100 GHz
At a channel spacing of

In another preferred example, the guard band has a range of about 1300 to 1320 nm, the low subband has a range of about 1295 to 1300 nm, and the high subband has a range of about 1320 to 1365 nm. Having. The carrier signal is transmitted on any one of about nine high-density WDM channels in the low sub-band and about 76 high-density WDM channels in the high sub-band. Each of these dense WDM channels within the low and high subbands is separated by a channel spacing of at least about 100 GHz.

According to a further feature of the present invention, there is provided a system and method for high density WDM dispersion compensation. In one example, the high-density WDM unit compensates for negative and / or positive dispersion in multiple carrier signals transmitted over monomodal fiber in each high-density WDM channel. Single-mode fiber is N
If it is a DSF, the high-density WDM dispersion compensation unit has a positive dispersion compensation unit (DCM) and a negative dispersion compensation unit (DCM).

The positive DCM compensates for the positive dispersion in each carrier signal transmitted on the NDSF in each high density WDM channel in the high subband. For example, a positive DCM may be a dispersion-shifted fiber segment and / or a chirped fiber Bragg designed to carry a negative dispersion value that is large enough to improve the magnitude of the positive dispersion value of the NDSF. It may be a lattice. Thus, the dispersion-shifted fiber segment and / or the chirped fiber Bragg grating compensate for the magnitude of the positive dispersion in each carrier signal transmitted over the NDSF in the respective high-density WDM channel at high subbands.

The negative DCM compensates for the negative dispersion in each carrier signal transmitted on the NDSF in the respective high-density WDM channel in the low sub-band. For example, a negative DCM may have a higher density WDM in the lower subband.
It may be a chirped fiber Bragg grating to compensate for the magnitude of the negative dispersion in each carrier signal transmitted on the NDSF in the channel.

Similarly, for DSF, the dense WDM DCM needs to be a negative DCM that compensates for the negative dispersion in each carrier signal in each dense WDM channel in the low and high subbands. There is only. For example, such a negative DCM is a positive variance value that compensates for the magnitude of the negative variance in each carrier signal transmitted on the DSF in the respective high-density WDM channel in the low and high subbands. May be a chirped fiber Bragg grating.

Further, the high-density WDM DCM according to the present invention can also compensate for the dispersion of the positive slope carried by a single mode fiber. For example, a chirped fiber Bragg grating can be constructed with low density WDM
It can be used to finely compensate for the positive dispersion slope in each carrier signal transmitted over a single mode fiber (NDSF or DSF) in the channel.

In one embodiment, the wavelength division multiplexing unit is optically coupled to a single mode fiber. This WDM unit multiplexes individual carrier signals (
multiplex) and outputs multiple carrier signals to a single mode fiber. For example, a wavelength division multiplexing unit may comprise at least one narrowband WDM unit and one or two directions (ie, unidirectional or bidirectional traffic).
May be multiplexed and / or demultiplexed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

Further embodiments, features, and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail with reference to the accompanying drawings.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the invention and, together with the description, explain the principles of the invention and enable those skilled in the art to utilize the invention. Help to be able to.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In these drawings, like reference numbers generally indicate identical or functionally similar elements. Further, the left-most number of a reference number typically identifies the drawing in which the reference number first appears.

The term “1310 nm band” is between about 1150 nanometers (nm) and 13
Refers to the wavelength band within the range of 85 nm.

FIG. 1 is a diagram illustrating dense wavelength division multiplexing (WDM) in the 1310 nm region 100 according to one embodiment of the present invention. According to one embodiment of the present invention, the optical communication link (not shown in FIG. 1) carries a high-density WDM optical signal at 100 in the 1310 nm band instead of or in addition to the erbium band. .
The optical communication link has at least one single-mode fiber, including but not limited to non-dispersion shifted fiber (NDSF) and dispersion shifted fiber (DSF). The DSF may have a linear tilt dispersion shifted fiber (LSF). An exemplary fiber link supporting high-density WDM according to the present invention is described in more detail in connection with FIGS.

As shown in FIG. 1, the carrier wavelength is selected from two regions (low sub-band 140 and high sub-band 160) on both sides of guard frequency band 120. Guard band 120 includes the zero dispersion wavelength λ ₀ of the monomodal fiber in the optical communication link, and separates low sub-band 140 and high sub-band 160.

In the embodiment shown in FIG. 1, the zero-dispersion wavelength λ ₀ is about 1312 ± 3 nm, as found in many placed fibers and new single-mode fibers in fiber optic networks. . The protection frequency band 120 is about 17
nm width and centered on λ ₀ . In particular, guard band 120 is approximately 130 to separate low sub-band 140 and high sub-band 160.
It covers the wavelength range of 3 to 1320 nm. The low sub-band 140 is approximately 1270-13
Covers the wavelength range of 03 nm. The high sub-band 160 is about 1320-1365 nm
Wavelength range.

Next, according to the present invention, one or more equally-spaced or non-equally-spaced channels (also referred to as carrier wavelengths) can be provided in low subband 140 and high subband 160. No channel is provided in the protection frequency band 120. Further, the width of the guard frequency band 120 can be set to minimize four-wave mixing (FWM). In one embodiment of the present invention, the guard frequency band centered on λ _{0 is such} that the absolute value of the variance in both the low and high sub-bands is
It has a width approximately equal to or greater than 0.5 ps / nm-km. In another embodiment, a guard band around 17 nm centered at λ ₀ is used to separate the low and high sub-bands. This means
Avoiding four-wave mixing by ensuring that closely spaced carriers co-propagate in a distributed environment, thereby reducing the phase required for efficient mixing over the length of the fiber "Wash out" coherence
. Thus, the density of the modulated carrier can occupy each subband 140, 160 without causing significant interference.

The wavelength values shown in FIG. 1 are exemplary and may vary.
The 1310 nm band is relatively wide and is bounded on the long end by the water absorption peak (about 1385 nm). In addition, the minimum wavelength limit imposed by the fiber geometry to guarantee single mode propagation (approximately 1150-127)
0 nm). Further, the protection frequency band 120, the sub-bands 140 and 160
May vary depending on the particular application as will be apparent to those skilled in the art given this description.

This high-density WDM multi-channel scheme according to the present invention allows for a much larger number of channels than would be expected for a general but narrower erbium band. Optical transducers and amplifiers for operating in the 1310 nm band are also relatively inexpensive.

As shown in FIGS. 2A and 2B, a relatively conservative high density W in accordance with the present invention
The DM design allows for a larger number of channels to be used than the erbium band WDM design. FIG. 2A is a diagram showing an example of 85 channels at 100 GHz intervals in the high-density WDM 1310 nm region of FIG.

FIG. 2B shows 100 channels at 100 GHz intervals, shown in FIG. 2A, having 85 channels in the low and high sub-bands and 15 channels in the guard band (which is not used). It is a table showing an example. Each channel is listed by a nominal frequency (f) (terahertz (THz)) and a center wavelength λ (nm).

In the example of FIG. 2A, the low sub-band 140 has nine channels at 100 GHz intervals between about 1295 and 1300 nm. High sub-band 160 is approximately 1
It has 76 channels between 320 and 1365 nm at 100 GHz intervals.
However, more channels can be reliably added to the lower sub-band 140 or the higher sub-band 160. For example, channels at wavelengths shorter than 1295 nm can be added. Depending on the particular design application and immunity, channels at wavelengths longer than 1365 nm, or channels in guard band 120 may also be used. Further, regarding the channel spacing, especially in order to add more channels at low bit rates, 100G
Hz. To further ensure signal separation, channel spacing greater than 100 GHz (or greater than 200 GHz) can be provided.

On the other hand, in the erbium band, the need for 100 GHz channel spacing translates into a wavelength range of about 0.8 nm. This means that only 40 WDM channels can be in the erbium fiber band. 1
If each optical carrier is modulated at a high data bit rate, such as 0 Gbit / s (Gb / s), a 200 GHz spacing is used between channels to prevent crosstalk. As a result, only 16 channels with 200 GHz spacing are about 15
It cannot be used efficiently in the operating range within the erbium band of 30-1561 nm. Thus, the conservative high-density WDM design of FIGS. 2A and 2B
100 channels 220% more than multiple channels in the erbium band
It is supported at GHz intervals.

By straddling the zero-dispersion wavelength λ ₀ , the two sub-bands 140 and 160 further know different dispersion values. As shown in FIGS. 3A to 3E, 131
Carriers in the low subband 140 and the high subband 160 in the 0 nm region know positive or negative dispersion along the monomodal fiber, depending on the type of fiber. Single mode fibers (NDSF and DSF) introduce positive tilt dispersion over the 1310 nm region.

FIG. 3A shows the dispersion for NDSF and DSF monomodal fibers in the 1310 nm region. NDSF fiber is in the 1310 nm region (about 12
CORN having a dispersion value of about -6.0 to 6.0 within 70 to 1374 nm).
ING® SMF-28 fiber. FIG. 3B shows about 1295-13
NDSF monomodal fiber in 80 channels in the 1310 nm region of 74 nm (
It is a figure which shows the dispersion | distribution range (about -1.595-5.329) regarding SMF-28). Thus, carriers in the lower subband 140 will see a negative variance along the NDSF. The carrier in the high sub-band 160 is an NDSF such as SMF-28.
Know the positive variance along.

However, as shown in FIGS. 3A and 3C to 3E, TRUEWAVE
DSF monomodal fibers, including RTM and linearly graded (LS) fibers, provide about -10-3 in the 1310 nm region (about 1270-1374 nm).
It has a negative variance value of zero. Next, the carriers in the low subband 140 and the carriers in the high subband 160 are along the DSF (at different negative variances)
Know the negative variance. FIG. 3C shows the dispersion for a DSF monomodal fiber in 80 channels in the 1310 nm region. For DSF fiber, the dispersion value is about −24.65 in the 1310 nm region (about 1295 to 1374 nm).
3 to -15.425.

FIG. 3D is a diagram illustrating dispersion for DSF TRUEWAVE® single mode fiber in 80 channels in the 1310 nm region. TRUEWAVE
For the ® fiber, the dispersion value is in the 1310 nm region (about 1295-1
374 nm) within the range of about −21.201 to 12.317.

FIG. 3E shows the DSF linear slope (linear-s) in 80 channels in the 1310 nm region.
FIG. 2 shows dispersion for a loped (LS) monomodal fiber. For the LS fiber, the dispersion value is about -278.81 to -17.876 in the 1310 nm region (about 1295 to 1374 nm).

The carriers in the low subband 140 know a negative variance along the NDSF. Carriers in the high subband 160 know the positive variance along the NDSF. The latter (positive dispersion) can be easily compensated for using one or more segments of conventional DSF or recently introduced LS fiber. The reason is that these are 1550 nm
Because it has a substantially negative dispersion in the 1310 nm band. Further, positive dispersion over the high sub-band 160 can be corrected and improved by one or more chirped fiber Bragg gratings, as is known in the art. Similarly, low subband 140 (and / or
Alternatively, the negative dispersion in the high sub-band 160) can be compensated by the chirped fiber Bragg grating. Such dispersion compensation will be described in more detail later with reference to FIG.

The high-density WDM in the 1310 nm band according to the present invention is described below with reference to the exemplary fiber link segments in FIGS. An exemplary high density WDM dispersion compensation module (DCM) is also described with reference to FIG.

FIG. 4 is a diagram illustrating an exemplary fiber link segment 400 supporting WDM in the 1310 nm region according to the present invention. The fiber link 400 is
A narrow wavelength division multiplexer (WDM) 410, a single mode fiber 415,
It has a two-way optical amplifier 420 and a high-density WDM dispersion compensation module (DCM) 440. WDM 410 may be any type of wavelength division multiplexer and / or demultiplexer, or combination of wavelength division multiplexer / demultiplexer. The single mode fiber 415 is a NDSF fiber (COR).
NING® SMF-28) and DSF fiber (TRUEWAW
® and LS) may be any type of monomodal fiber. The two-way optical amplifier 420 has a wavelength of 1310 nm.
It may be any type of two-way optical amplifier that amplifies the band wavelength. High density WDM
DCM 440 is further described with reference to FIG. Other optical components that can be used, such as combiners, splitters, etc., are known in WDM communications. Optical emitters and receivers (not shown) are also provided for generating and detecting carrier signals on the respective high-density WDM channels (ie, low and high sub-band channels).

In the example of FIG. 4, fiber link segment 400 is two-way carrying traffic in two directions along the same fiber. In a long haul fiber network, for example, three directions may be east and west between two cities. Accordingly, WDM 410 receives carriers for dense WDM channels traveling in one direction (ie, west) and multiplexes these carriers onto monomodal fiber 415. On the other hand, WDM 410 receives carriers for dense WDM channels traveling in the other direction (ie, east) and demultiplexes these carriers from monomodal fiber 415.

In general, any combination of high density WDM channels at 1310 nm can be allocated to carry signals in one or two directions over fiber link 400. However, in one embodiment shown in FIG. 4, carriers traveling in one direction (west) are assigned channels in the low sub-band 140. Carriers traveling in the other direction (east) are assigned channels in the high sub-band 160. Further, the fiber link 400 can be modified to be two unidirectional links.

FIG. 5 is a diagram illustrating another example of a fiber link segment 400 that supports WDM in the 1310 nm region according to the present invention. In FIG. 5, W
DM 410 is replaced by four narrow WDMs 504-507 and a WDM 503, which can be a narrow, coarse, or wideband WDM. In FIG. 5, to minimize the possibility of crosstalk or other interference, the four carriers in each of the four low subband channels traveling in one direction (west) are multiplexed and W
Received at WDM 504 for transmission to DM 503. One direction (west)
The other four carriers in each of the four low subband channels traveling to the WDM 503 are received at WDM 506 for multiplexing and transmission to WDM 503. Next, WDM 503 multiplexes the eight low sub-band channels for transmission on monomodal fiber 415.

Considering the other direction (east), WDM 503 is a single-mode fiber 41
Demultiplex the eight high sub-band channels received into two groups of five to four high sub-band channels. Next, one group of four respective high sub-band channels traveling in one direction (east) is received at WDM 505 for further demultiplexing and transmission to the optical receiver. The other group of four carriers in each of the four high sub-band channels traveling in one direction (east) is received at WDM 507 for demultiplexing and transmitting to the optical receiver.

For clarity, only one end of fiber link segment 400 is shown in FIGS. 4 and 5, but the other end will be readily apparent to one of ordinary skill in the art given this description. Is similar. Further, for clarity, WDM41
For 0, only one low subband and one high subband are shown. However, as described above, any number of channels may be provided in low subband 140 and / or high subband 160. Similarly, FIG.
For illustrative purposes, 16 channels are shown in four groups. The invention is not so limited. The reason is that, as described above, in the low subband 140 and / or the high subband 160, an arbitrary number of channels can be allocated between the WDMs 504 to 507 in the high-density WDM in the 1310 nm region. To further reduce the likelihood of crosstalk or other interference, different groups of channels within the low subband 140 can be assigned to move in different directions. (Similarly, high subband 1
Different groups of channels within 60 can be assigned to move in different directions. )

FIG. 6 illustrates an exemplary high density WDM dispersion compensation module (DCM) 440 for use with NDSF fiber in more detail. The high-density WDM DCM 440 has two wavelength splitters / combiners 620,640. A negative dispersion compensation unit (negative DCM) 660 and a positive dispersion compensation unit (positive DCM) 680 are provided in parallel between the wavelength splitters / combiners 620 and 640. High-density WDM DCM 440 is particularly important for distributed fiber media and long-haul fiber links.

As described above in connection with FIGS. 3A and 3B, the carriers in the high subband 160 know the positive dispersion along the NDSF, and are thus passed through the wavelength splitter / combiners 620, 640, Passed to positive DCM 680. Positive DCM 680 compensates (in magnitude and / or slope) for positive dispersion along the NDSF. For example, positive DCM 680 may have one or more segments of conventional DSF or recently introduced LS fiber. The reason is,
This is because they are optimized for 1550 nm and can transmit substantially negative dispersion in the 1310 nm band. Further, positive DCM 680 may include a chirped fiber Bragg grating to compensate for positive dispersion, as is known in the art. For example, Agrawal, "Fiber-Optic Communicat
ion Systems "Second Ed. (John Wiley & Sons: New York 1997), section 9.6.
See chapter 2, chapter 9, pp. 425-466.

The carriers in the low sub-band 140 know the negative dispersion along the NDSF and are thus passed through the wavelength splitters / combiners 620, 640 and have a negative DC
Passed to M660. Negative DCM 660 compensates for negative dispersion along the NDSF. For example, the negative DCM 660 may be a chirped fiber Bragg grating set to compensate for negative dispersion, as is known in the art.

Further, as described above in connection with FIGS. 3A and 3C-3E, if the monomodal fiber 415 is a DSF (DS, TRUEWAVE®, or LS) fiber, the negative dispersion Is the lower subband 140 and the higher subband 16
It can occur at both zero. In this case, the dense WDM DCM 440 only needs to have a negative DCM 660. Next, all channels in low subband 140 and high subband 160 are negative DCM6
60 compensates for the negative dispersion. In other words, carriers in the dense WDM channel in the low and high subbands pass through one or more chirped fiber Bragg gratings to compensate for negative dispersion along the DSF.

Further, the high density WDM DCM 440 according to the present invention can also compensate for the positive slope dispersion carried by single mode fiber. For example, for a chirped fiber Bragg grating, a single-mode fiber (NDSF or DSF) in each high-density WDM channel in the low and high subbands
) Can be used to finely compensate for the slope of the positive dispersion in each carrier signal transmitted above. For such a chirped fiber Bragg grating, it can be separately coupled to the high density DCM 440 or the negative DCM 66
It can have either or both of zero and positive DCM680.

High-speed fiber optic networks or links using high-density WDM in the 1310 nm region according to the present invention can have, but are not limited to, OC-48 or OC-192 bit rates. For an OC-48 bit rate of about 2.5 Gb / s, the fiber type (SMF-28, SMF-
DS, SMF-LS, and TRUEWAVE (registered trademark)) can be used. For an OC-192 bit rate of about 10 Gb / s, NDSF (SM
F-28) Fiber is preferred (with such high bit rates, the spacing between channels for channel planning for low subband 140 and high subband 160 may need to be larger).

FIG. 7 is a graph illustrating an example of a dispersion limited distance in a typical and optimal case for OC-48 optical communications carried on DSF monomodal fiber. In a normal case, the distance over which the OC-48 carrier signal can move is -10 ps / nm-km.
Is limited to about 1750 km, and -30 ps / nm-k
For high dispersion values of m, it is limited to about 198 km. When optimal, OC-4
The distance that an 8-carrier signal can travel is limited to about 2900 km for a low dispersion value of -10 ps / nm-km, and about 300 km for a high dispersion value of -30 ps / nm-km. You.

FIG. 8 is a graph illustrating an example of the loss in transmitted power versus distance. The distance over which the OC-48 carrier signal can move and be detected satisfactorily is limited by the power of the transmitter. As shown in FIG. 8, the distance ranges from 1 to 21.
For an OC-48 signal transmitted by a transmitter having a transmitter power of dBm, it varies between about 60-100 km. The plot in FIG. 8 assumes a minimum receiver level during normal operation of about -26 dBm. As is known in the prior art, the unit "dBm" is a unit derived to represent power and is defined as power (dBm) = ₁₀ log ₁₀ (power / 1 mW). See Agrawal, "Decibel Units", Appendix B, pp. 535-536. The examples in FIGS. 7 and 8 are not intended to limit the scope of the present invention. One of ordinary skill in the art, given this description, will be aware of the various link and network designs and components (eg, higher transmitter power, low dispersion fiber, optical amplifier or regenerator frequency spacing, and It is understood that various dispersion compensation modules (DCMs) can be used to achieve long-distance fiber optic communications using high-density WDM in the 1310 nm band according to the present invention.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only. It will be understood by those skilled in the art that various changes may be made in the form and details herein without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, the scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[Brief description of the drawings]

FIG. 1 illustrates dense wavelength division multiplexing (WDM) in the 1310 nm region, according to one embodiment of the present invention.

FIG. 2A shows 100 GHz within the high-density WDM 1310 nm region of FIG. 1;
FIG. 2B shows an example of 85 channels in the interval, where 2B shows 85 channels in the low and high sub-bands and 1 in the guard frequency band as shown in 2A.
It is a table | surface which shows the example of 100 channels of 100 GHz space | interval which has 5 channels.

3A shows dispersion for NDSF and DSF monomodal fiber in the 1310 nm region, 3B shows dispersion for NDSF monomodal fiber in 80 channels in the 1310 nm region, and 3C shows , 1
3D shows the dispersion for a DSF single-mode fiber in 80 channels in the 310 nm region, and 3D shows the dispersion for a DSF TRUE WAVE® single-mode fiber in 80 channels in the 1310 nm region. Is
FIG. 3 shows the dispersion for a DSF linear-sloped (LS) single-mode fiber in 80 channels in the 1310 nm region.

FIG. 4 illustrates an exemplary fiber link segment supporting WDM in the 1310 nm region, according to the present invention.

FIG. 5 illustrates another exemplary fiber link segment supporting WDM in the 1310 nm region according to the present invention.

FIG. 6 shows an example of the high-density WDM dispersion compensation module of FIGS. 4 and 5 in more detail.

FIG. 7 is a graph showing dispersion limited distance in a near typical and optimal case for OC-48 optical communications carried on NDSF single mode fiber.

FIG. 8: OC-48 and OC carried on NDSF single mode fiber
FIG. 4 is a graph showing the loss limiting distance in a nearly typical and optimal case for -192 optical communications.

[Explanation of symbols]

 100 1310 nm region 120 guard frequency band 140 low subband 160 high subband 400 fiber link segment 410 wavelength division multiplexer (WDM) 415 single mode fiber 420 two-way optical amplifier 440 high density WDM dispersion compensation module (DCM) 503 wavelength division multiplexer (WDM) 504-507 Narrow wavelength division multiplexer (WDM) 620,640 Wavelength splitter / combiner 660 Negative dispersion compensation unit (negative DCM) 680 Positive dispersion compensation unit (positive DCM)

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), CA, JP, MX, SG F term (reference) 2H050 AC84 AD01 AD16 5K002 CA01 DA02 FA02

Claims (32)

[Claims] 1. A method for providing dense wavelength division multiplexing during optical communications, comprising: establishing a guard band having a zero dispersion wavelength λ ₀ of a monomodal fiber within a 1310 nm band. Transmitting a first signal on a single-mode fiber; transmitting a second signal on a single-mode fiber, wherein the guard frequency band comprises a low sub-band within a 1310 nm band; The method of claim 1 wherein the first signal has a wavelength in the low subband and the second signal has a wavelength in the high subband. 2. High-density wavelength division multiplexing (de) during multi-channel optical communication.
establishing a guard band having a zero-dispersion wavelength λ ₀ of the monomodal fiber in the 1310 nm band, and providing a respective high density on the monomodal fiber. Transmitting a plurality of carrier signals in a WDM channel, wherein the guard frequency band separates a low sub-band and a high sub-band in a 1310 nm band, and wherein the carrier signal is the low sub-band in a 1310 nm band. And having a wavelength in at least one of the high sub-bands. Wherein the establishing step, the guard band to have a zero-dispersion wavelength lambda ₀ of the single style fiber, a step of establishing within the 1310nm band, the zero-dispersion wavelength lambda ₀ is about 1309nm~1315nm The method of claim 2, wherein 4. The step of establishing a protection frequency band having a width having a zero-dispersion wavelength λ ₀ of a single-mode fiber within a band of 1310 nm, wherein the width of the protection frequency band is low. The absolute value of the variance in both the sub-band and the high sub-band is approximately equal to 0.5 ps / nm-km or 0.5 ps / n
Method according to claim 2, characterized in that it is set to be greater than m-km, so that four-wave mixing (FWM) is minimized. 5. The method according to claim 1, wherein the establishing step comprises establishing a protection frequency band having a width of at least 2 nm having a zero-dispersion wavelength λ ₀ of a monomodal fiber within a 1310 nm band. 3. The method according to 2. 6. The step of establishing a protection frequency band having a width of about 17 nm having a zero-dispersion wavelength λ ₀ of a monomodal fiber in a 1310 nm band. 3. The method according to 2. 7. The establishing step comprises establishing a guard frequency band having a range of about 1300 nm to 1320 nm within a 1310 nm band, wherein the guard frequency band has a low sub-band having a range of about 1270 nm to 1300 nm. And about 13
3. The method according to claim 2, further comprising separating the high sub-band having a range of 20 nm to 1365 nm. 8. The method of claim 2, wherein the establishing step further comprises the step of separating the high-density WDM channels in low and high subbands by a channel spacing. 9. The method of claim 8, wherein said spacing step comprises spacing said high density WDM channels in low and high subbands by a channel spacing of at least about 100 GHz. . 10. The step of establishing a protection frequency band having a range of about 1300 nm to 1320 nm in a 1310 nm band, wherein the protection frequency band has a low sub-band having a range of about 1295 nm to 1300 nm. And about 1
Separating a high sub-band having a range of 320 nm to 1365 nm, wherein the establishing comprises about nine of the high density WDM channels in the low sub-band and about nine of the high density WDM channels in the high sub-band. 3. The method of claim 2, further comprising the step of separating the 76 channels by a channel spacing of at least about 100 GHz. 11. The method further comprises compensating for at least one of a negative dispersion and a positive dispersion in a plurality of carrier signals transmitted over a single mode fiber in each high density WDM channel. 3. The method of claim 2, wherein: 12. The monomodal fiber is a non-dispersion shifted fiber,
And transmitting the plurality of carrier signals in each of the high-density WDM channels over a non-dispersion shift fiber,
Each of the carriers having wavelengths in the low and high sub-bands within a 310 nm band, and wherein the dispersion compensating step comprises transmitting each carrier transmitted over a non-dispersion shifted fiber in a respective high density WDM channel in a high sub-band Compensating for positive dispersion in the signal; and compensating for negative dispersion in each carrier signal transmitted over the non-dispersion shifted fiber in each high density WDM channel in the low sub-band. The method according to claim 11, wherein: 13. The monomodal fiber is a dispersion-shifted fiber, and the transmitting step transmits a plurality of carrier signals in respective high-density WDM channels over the dispersion-shifted fiber, wherein the carrier signal is , 131
A carrier signal transmitted over a dispersion-shifted fiber in a respective high-density WDM channel in a high sub-band having wavelengths in the low and high sub-bands within a 0 nm band; Compensating for the negative dispersion in, and compensating for the negative dispersion in each carrier signal transmitted over the dispersion-shifted fiber in each high-density WDM channel in the low sub-band. The method according to claim 11. 14. The method of claim 11, further comprising, before the transmitting step, multiplexing a plurality of carrier signals. 15. A multi-channel optical communication system comprising: a single mode fiber having a zero dispersion wavelength λ _0; and a plurality of carrier signals traveling through the single mode fiber, wherein the carrier signal is , Having a wavelength in at least one of a low subband and a high subband within the 1310 nm band, wherein the low subband and the high subband have a zero dispersion wavelength λ ₀ of the monomodal fiber. A system characterized by being separated by a band. 16. The system according to claim 15, wherein the zero dispersion wavelength λ ₀ is in a range from about 1309 nm to 1315 nm. 17. The protection frequency band is a zero-dispersion wavelength λ of a single-mode fiber. ₀ And the width of the guard frequency band is such that the absolute value of the variance in both the low and high subbands is approximately equal to 0.5 ps / nm-km,
Or greater than 0.5 ps / nm-km, which results in four-wave mixing (F
16. The system according to claim 15, wherein WM) is set to be minimized.
Stem. 18. The system according to claim 15, wherein the guard band has a width of at least 2 nm. 19. The system of claim 15, wherein said guard band has a width of about 17 nm. 20. The protection frequency band having a range of about 1300 nm to 1320 nm, the low sub-band having a range of about 1270 nm to 1300 nm,
The system of claim 15, wherein the high sub-band has a range from about 1320nm to 1365nm. 21. The plurality of carrier signals transmit data on respective high-density WDM channels in the low sub-band and the high sub-band, wherein the high-density WDM channels are separated by a channel spacing. The system according to claim 15, characterized in that: 22. The system of claim 21, wherein said channel spacing is at least about 100 GHz. 23. The protection frequency band has a range of about 1300nm to 1320nm, the low subband has a range of about 1295nm to 1300nm, and the high subband has a range of about 1320nm to 1365nm. And wherein the plurality of carrier signals comprises about nine of the high density WDs in a low sub-band.
An M channel and one of the approximately 76 dense WDM channels in a high sub-band, each of the dense WDM channels in a low sub-band having a channel spacing of at least about 100 GHz. The system of claim 15, comprising: wherein each of the dense WDM channels in a high sub-band has a channel spacing of at least about 100 GHz. 24. A high-density WDM dispersion compensation unit that compensates for at least one of negative dispersion and positive dispersion in the plurality of carrier signals transmitted on a single mode fiber in each high-density WDM channel. The system of claim 15, further comprising: 25. The monomodal fiber is a non-dispersion shifted fiber,
And the high-density WDM dispersion compensation unit comprises: a positive dispersion compensation unit that compensates for positive dispersion in each carrier signal transmitted on the non-dispersion shifted fiber in each high-density WDM channel in the high subband. And a negative dispersion compensation unit for compensating for negative dispersion in each carrier signal transmitted on the non-dispersion shifted fiber in each high density WDM channel in the low subband. 25. The system according to 24. 26. The positive dispersion compensating unit comprises a dispersion shifted fiber segment and a positive dispersion of each carrier signal transmitted on the non-dispersion shifted fiber in a respective high density WDM channel in the high subband. At least one of: a chirped fiber Bragg grating to compensate for the magnitude; and the negative dispersion compensation unit comprises a respective high density W in the low sub-band.
26. The system of claim 25, comprising a chirped fiber Bragg grating to compensate for the magnitude of the negative dispersion in each carrier signal transmitted on a non-dispersion shifted fiber in a DM channel. 27. The monomodal fiber comprises a dispersion-shifted fiber, and the high-density WDM dispersion compensating unit is configured to control the dispersion shift in a high-density WDM channel in the high subband and the low subband. The system of claim 24, further comprising a negative dispersion compensation unit that compensates for negative dispersion in each carrier signal transmitted on the fiber. 28. The negative dispersion compensating unit, wherein the magnitude of the negative dispersion in each carrier signal transmitted on the dispersion-shifted fiber in the high-density WDM channel in the high sub-band and the low sub-band, respectively. 28. The system of claim 27, comprising a chirped fiber Bragg grating to compensate for: 29. A wavelength division multiplexing unit optically coupled to said monomodal fiber, said wavelength division multiplexing unit multiplexing individual carrier signals and combining said plurality of carrier signals. The system of claim 15, wherein output is to the single mode fiber. 30. The wavelength division multiplexing unit comprising at least one narrowband W
30. The system according to claim 29, comprising a DM unit. 31. The wavelength division multiplexing unit multiplexes a first group of individual carrier signals traveling in one direction, and multiplexes the first group of multiplexed carrier signals into the single mode fiber. And demultiplexes a second group of individual carrier signals traveling in the other direction, and
30. The system of claim 29, wherein outputting a second group of the demultiplexed carrier signals. 32. A method for providing multi-channel optical communication, comprising: establishing a guard band in a 1310 nm band that separates a low sub band and a high sub band in a 1310 nm band; Transmitting a plurality of carrier signals, the carrier signals having wavelengths in at least one of the low subband and the high subband within a 1310 nm band.