WO2000051268A1 - Systeme de transmission a mode spatial d'ordre eleve - Google Patents

Systeme de transmission a mode spatial d'ordre eleve Download PDF

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Publication number
WO2000051268A1
WO2000051268A1 PCT/US2000/004528 US0004528W WO0051268A1 WO 2000051268 A1 WO2000051268 A1 WO 2000051268A1 US 0004528 W US0004528 W US 0004528W WO 0051268 A1 WO0051268 A1 WO 0051268A1
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WO
WIPO (PCT)
Prior art keywords
optical
spatial mode
dispersion
transmission system
energy
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PCT/US2000/004528
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English (en)
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WO2000051268B1 (fr
Inventor
Yochay Danziger
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Lasercomm, Inc.
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Publication date
Priority claimed from US09/510,027 external-priority patent/US6418256B1/en
Priority claimed from US09/507,001 external-priority patent/US6360045B1/en
Application filed by Lasercomm, Inc. filed Critical Lasercomm, Inc.
Priority to AU32401/00A priority Critical patent/AU3240100A/en
Publication of WO2000051268A1 publication Critical patent/WO2000051268A1/fr
Publication of WO2000051268B1 publication Critical patent/WO2000051268B1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
    • G02B6/03638—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 3 layers only
    • G02B6/03644—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 3 layers only arranged - + -
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02004—Optical fibres with cladding with or without a coating characterised by the core effective area or mode field radius
    • G02B6/02009—Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres
    • G02B6/02023—Based on higher order modes, i.e. propagating modes other than the LP01 or HE11 fundamental mode
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02214—Optical fibres with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219—Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02228—Dispersion flattened fibres, i.e. having a low dispersion variation over an extended wavelength range
    • G02B6/02238—Low dispersion slope fibres
    • G02B6/02242—Low dispersion slope fibres having a dispersion slope <0.06 ps/km/nm2
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03605—Highest refractive index not on central axis
    • G02B6/03611—Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/14—Mode converters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2581—Multimode transmission
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02214—Optical fibres with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219—Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02252—Negative dispersion fibres at 1550 nm
    • G02B6/02257—Non-zero dispersion shifted fibres, i.e. having a small negative dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between - 1.0 to - 10 ps/nm.km for avoiding nonlinear effects
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02214—Optical fibres with cladding with or without a coating tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
    • G02B6/02219—Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm
    • G02B6/02266—Positive dispersion fibres at 1550 nm
    • G02B6/02271—Non-zero dispersion shifted fibres, i.e. having a small positive dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between 1.0 to 10 ps/nm.km for avoiding nonlinear effects

Definitions

  • the invention relates to optical communication systems, and more specifically to methods and apparatus for utilizing optical transmission fibers which support higher order spatial modes.
  • Multimode fibers which typically support hundreds of optical modes are subject to modal dispersion.
  • Single-mode optical fibers which exclusively support a single optical spatial mode, namely the LPoi spatial mode also known as the fundamental mode, are typically used today in optical communication systems.
  • the transmission loss in these SMFs is generally minimized for wavelengths in the range of 1300 and 1550nm typically utilized for long-distance communications.
  • Single mode fibers are typically utilized because they exhibit virtually no signal quality degradation as a result of modal dispersion.
  • the pulses in this range propagate through an SMF, their waveforms tend to spread because of chromatic dispersion resulting in limitations on the bit rate and the transmission distance.
  • the total chromatic dispersion experienced is a combination of material dispersion and waveguide dispersion, which may be of opposite sign.
  • the total dispersion is approximately 17ps/nm-km. This primarily results from material dispersion.
  • S/N signal-to-noise ratio
  • Dispersion slope is defined as the rate of change of the total chromatic dispersion of the fiber as the wavelength changes. In a conventional non-shifted SMF used for the communication wavelength band of 1550nm the dispersion slope is about 0.06ps/nm 2 -km.
  • Compensating for positive dispersion by using dispersion compensating fibers which have low attenuation and high negative dispersion values is well known in the art (See, for example, US Patent 5,185,827, US Patent 5,261,016 and US Patent 5,361,319). However, compensating for negative dispersion may require long lengths of fiber (See, for example, US Patent 4,261,639). Most systems utilize some method of compensating for dispersion, so that the received signal is not substantially dispersed or spread.
  • high dispersion is desired locally throughout the system and dispersion close to zero is desired for the overall system or repeating block.
  • Nine spans of negative dispersion fiber are used, and are compensated by a single span of positive dispersion fiber. This method is well known to those skilled in the art and is referred to as concatenation.
  • a span is defined as the length of fiber between amplifiers, or between the transmitter or receiver and the nearest amplifier.
  • a single mode fiber (SMF) with negative slope typically has a small effective area (A eff ), which leads to increased undesired non-linear effects in high power systems.
  • a eff effective area
  • the solution requires the use of a subspan of a large effective area fiber, which has a large dispersion slope at the beginning of the span for the effective length of nonlinear interactions, followed by a subspan of a different fiber profile for the balance of the span.
  • U.S. Patent 5,781,673 describes another solution for resolving the dispersion slope by utilizing an additional span of dispersion slope compensation fiber.
  • this solution adds complexity to the system, and may enhance undesirable losses as well.
  • the invention relates, in one embodiment, to an optical transmission system for transmitting an optical signal having optical energy.
  • the system in another embodiment, includes at least one transmission span including an optical waveguide.
  • the transmission span transmits substantially all of the optical energy in a single high order spatial mode.
  • the single high order spatial mode is the LP 0 2 spatial mode.
  • the optical transmission system in yet another embodiment, further includes at least one additional transmission span.
  • the transmission span in another embodiment, includes an optical fiber.
  • the optical waveguide in one embodiment, has a dispersion and a dispersion slope for a given transmission bandwidth.
  • the dispersion includes at least material dispersion, and the absolute value of the dispersion is substantially between zero and the material dispersion.
  • the dispersion of the optical waveguide is negative over the transmission bandwidth.
  • the dispersion of the optical waveguide is positive over the transmission bandwidth.
  • the dispersion slope of the optical waveguide is positive, negative, or nominally zero.
  • the invention further relates to an optical transmission system which includes a spatial mode transformer positioned to receive an optical signal.
  • the spatial mode transformer transforms the optical energy of the optical signal from a low order spatial mode to a high order spatial mode.
  • the system further includes an optical transmission waveguide in optical communication with a spatial mode transformer, and the optical transmission waveguide transmits substantially all of the optical energy in the high order spatial mode.
  • the high order spatial mode is the LP02 spatial mode.
  • the low order spatial mode is the fundamental spatial mode.
  • the system includes a second spatial mode transformer in optical communication with the optical waveguide, and the second spatial mode transformer transforms the optical energy in the high order spatial mode to a low order spatial mode.
  • the invention further relates to a method for transmitting an optical signal having optical energy substantially in a single high order spatial mode.
  • the method includes the steps of receiving the optical signal having optical energy in the single high order spatial mode, and transmitting the optical signal having optical energy in the single high order spatial mode through a transmission span.
  • the transmission span includes an optical waveguide.
  • Another aspect of the invention includes a method for transmitting an optical signal having optical energy in a first spatial mode.
  • the method includes the steps of receiving an optical signal having optical energy in the first spatial mode, transforming the optical energy in the first spatial mode to optical energy in a second spatial mode, and transmitting the optical energy in the second spatial mode through an optical transmission waveguide.
  • the method further includes the step of transforming the optical energy in the second spatial mode to optical energy in a third spatial mode.
  • the first spatial mode is the LP 01 spatial mode.
  • the second spatial mode is the LP 02 spatial mode.
  • the third spatial mode is the LP 01 spatial mode.
  • Fig. 1 illustrates an embodiment of a refractive index profile of a fiber constructed according to the present invention.
  • Fig. 2 illustrates the chromatic dispersion and dispersion slope of the refractive index profile shown in Fig. 1.
  • Fig. 3 illustrates the waveform of the LP 0 ⁇ spatial mode for the refractive index profile shown in Fig. 1.
  • Fig. 4 illustrates the waveform of the LPo spatial mode for the refractive index profile shown in Fig. 1.
  • Fig. 5 illustrates the waveform of the LP 2 ⁇ spatial mode for the refractive index profile shown in Fig. 1.
  • Fig. 6 illustrates the waveform of the LPn spatial mode for the refractive index profile shown in Fig. 1.
  • Fig. 7a illustrates another embodiment of a manufactured refractive index profile of a fiber constructed according to the present invention.
  • Fig. 7b illustrates the chromatic dispersion and dispersion slope of the refractive index profile shown in Fig. 7a.
  • Fig 8 illustrates the total dispersion for three different fibers including an embodiment of a fiber constructed according to the present invention.
  • Fig. 9 illustrates another embodiment of a refractive index profile of a fiber constructed according to the present invention.
  • Fig. 10 illustrates the chromatic dispersion and dispersion slope of the refractive index profile shown in Fig. 9.
  • Fig. 1 la illustrates another embodiment of a refractive index profile of a fiber constructed according to the present invention.
  • Fig. 1 lb illustrates the chromatic dispersion and dispersion slope of the refractive index profile shown in Fig. 11a.
  • Fig. 12 illustrates a block diagram of a conventional transmission system known to the prior art.
  • Fig. 13 illustrates a block diagram of one embodiment of a transmission system constructed according to the present invention.
  • Fig. 14 illustrates a block diagram of another embodiment of a transmission system constructed according to the present invention.
  • Fig. 15 illustrates a block diagram of another embodiment of a transmission system utilizing a dispersion-compensating device constructed according to the present invention.
  • Fig. 16 illustrates the resultant effective dispersion in ps/nm over the length of an example transmission system constructed according to the present invention.
  • the present invention in one embodiment typically utilizes a few mode optical transmission waveguide.
  • This is an optical waveguide which typically supports only a few spatial modes.
  • the waveguide is an optical fiber.
  • the fiber design is optimized for the transmission of substantially a single higher order spatial mode. In higher order spatial modes the energy is less concentrated in a given region of the waveguide and, therefore a larger effective area (A ef r) may be achieved. Consequently, non-linear effects which are proportional to the energy concentration in the fiber will be suppressed.
  • Another advantage of using a high order spatial mode in the transmission fiber is the ability to control the chromatic dispersion and the dispersion slope of the high order spatial modes.
  • fibers which support higher order spatial modes may be designed by adjusting their refractive index profile so that they will have the desired dispersion and dispersion slope.
  • an extremely low dispersion slope on the order of 0.02ps/nm 2 -km or lower may be achieved, and fibers with either positive or negative dispersion and positive or negative dispersion slope may be designed according to one aspect of the invention.
  • the following description specifies a higher order spatial mode being the LP 02 spatial mode, however this is not meant to be limiting in any way, and can be applied to other high order spatial modes as well, which will be apparent to those skilled in the art.
  • Fig. 1 illustrates one embodiment of a refractive index profile 10 according to the present invention.
  • the area 12 at the center of the core of the fiber is an area of depressed refractive index. Minimizing the germanium dopant in area 12 of the fiber creates this depressed index.
  • This area of depressed index 12 functions to increase the effective area (A eff ) of the fiber, and helps to differentiate the propagation constants of the spatial modes. This reduces mode coupling and the resultant Multi-Path Interference (MPI).
  • MPI Multi-Path Interference
  • the increased effective area (A eff ) results in reduced non-linear effects.
  • the increase in refractive index at region 14 guides the
  • the refractive index in region 12 is substantially the same as the refractive index in region 16 and the cladding region 20, although other embodiments can be designed by introducing different dopants.
  • the refractive index increase at region 18 is allowed to vary substantially, and functions to limit the expansion of the LP 0 2 spatial mode into the cladding and thus to limit macrobending losses.
  • the profile supports at least three spatial modes in the transmission bandwidth centered approximately in the region of 1550nm, including the LPoi, LPo 2 , LPi i and LP 21 spatial modes.
  • the calculated characteristics of the fiber determined for the LP 02 spatial mode for this profile are:
  • a ef for the LP 02 spatial mode is approximately 230 ⁇ m 2 .
  • Attenuation is about 0.2 - 0.4dB/km.
  • Cut off for the LP 02 spatial mode is greater than 1900nm.
  • Dispersion is approximately 3.7ps/nnvkm at 1550nm.
  • Dispersion slope is approximately 0.0216ps/nm -km.
  • Dispersion zero is adjustable between 1450 to 1520nm.
  • the calculated macrobending loss is acceptable with an n eff of 1.4454 for the LP 02 spatial mode.
  • Fig. 2 illustrates the total chromatic dispersion and dispersion slope of the refractive index profile 10 shown in Fig. 1 for a signal in the LP02 spatial mode.
  • the total chromatic dispersion 24 is the sum of the material dispersion 22 and the waveguide dispersion 26.
  • the waveguide dispersion 26 can be modified so as to arrive at the desired dispersion slope and zero dispersion point.
  • a unique feature of the fiber profile 10 of Fig. 1 is the extremely low slope of the total chromatic dispersion 24, which is approximately 0.02ps/nm -km.
  • Fig 3 illustrates the waveform 28 for the LP 0 ⁇ spatial mode in the refractive index profile 10 of Fig. 1.
  • the X-axis represents radius in microns from the core center, and the Y-axis represents the energy intensity in arbitrary units. Due to the depression 12 in the fiber profile, a depressed area 30 appears in the waveform, which serves to spread the energy away from the center of the core. Region 32 indicates the energy intensity at a point approximately 3 ⁇ m from the core center.
  • Fig. 4 illustrates the waveform 34 for the LP 02 spatial mode in the refractive index profile
  • Depression 12 in the fiber profile (Fig. 1) forms well 36 in the waveform of the LP 0 2 spatial mode which is minimal in comparison to well 30 of the waveform for the LPoi spatial mode shown in Fig. 3.
  • the LP 02 spatial mode has minimal energy at point 38, approximately 3 ⁇ m from the core center. Note that region 38 of the LP 02 spatial mode corresponds to region 32 of the LPoi spatial mode shown in Fig. 3. Thus at the point where the LP 02 spatial mode has minimal energy, the LPoi spatial mode contains significant energy. It should also be noted by comparing waveform 34 with fiber profile 10 of Fig. 1, that the modal energy is substantially contained within the core area 14 and area 18 of increased refractive index.
  • Fig. 5 illustrates the waveform 40 for the LP 21 spatial mode in the refractive index profile
  • Fig. 6 illustrates the waveform 44 for the LP* 1 spatial mode in the refractive index profile
  • a further method known to the art for removing higher order modes other than the desired high order mode involves curving a length of the waveguide to a smaller radius. Higher order modes will then escape from the cladding. The radius of the curvature is chosen to be small enough to attenuate higher order modes, but to maintain the desired high order mode. This procedure may, in one embodiment, be utilized in defining the radius of a dispersion compensation fiber reel.
  • Fig. 7a illustrates a fiber profile similar to that of Fig. 1 without the core dip 12, and with the smoother transitions generally seen in actual fabrication.
  • the fiber is designed with a single central core area 52 which is used to guide the LP 02 spatial mode, while the depression in index at region 54 is used to control the dispersion slope.
  • the dip near the core center is primarily a result of the manufacturing process and is not caused by a planned dopant.
  • the refractive index in region 54 is less than that of the cladding 58, although other embodiments can have different refractive index profile designs. Changing the height and width of regions 52, 54 and 56 will substantially alter the resultant characteristics of the fiber.
  • the increase in refractive index at region 56 functions to limit the expansion of the LP 02 spatial mode into the cladding.
  • the characteristics are similar to the characteristics of fiber profile 10, with an A eff of 270 ⁇ m 2 , but with increased mode coupling.
  • Fig. 7b illustrates the total chromatic dispersion and dispersion slope of the refractive index profile 50 shown in Fig. 7a for a signal in the LP 0 2 spatial mode.
  • the total chromatic dispersion 62 is the sum of the material dispersion 60 and the waveguide dispersion 64.
  • the waveguide dispersion can be modified so as to arrive at the desired dispersion slope and zero dispersion point.
  • a unique feature of the fiber profile 50 of Fig. 7a is the low slope of the total chromatic dispersion 62, which is approximately 0.042ps/nm 2 -km, with a dispersion at 1550nm of 5.2ps/nn ⁇ km.
  • Fig. 8 illustrates the total dispersion for three different fibers including a fiber manufactured according to the present invention.
  • Line 70 represents a typical single mode fiber such as SMF-28TM produced by Corning Incorporated, Corning, New York.
  • SMF-28TM produced by Corning Incorporated, Corning, New York.
  • Such a fiber typically has a dispersion of between about 12ps/nm-km to about 18ps/nn ⁇ km depending on wavelength. For example, at approximately 1550nm this fiber can achieve a dispersion of
  • Line 72 is a single mode fiber (SMF) with low dispersion, from approximately 2.0 to
  • Line 74 represents a high order mode transmission optical fiber (THOM) according to the present invention.
  • the present fiber exhibits relatively low dispersion on the order of between 2 and 4ps/nm/km across a broad wavelength range and an extremely low dispersion slope of approximately 0.02ps/nm 2 -km.
  • Fig. 9 illustrates another embodiment of a refractive index profile 80 of a fiber constructed according to the present invention.
  • the area 82 at the center of the core of the fiber is an area of depressed index. Minimizing the germanium dopant in area 82 creates this depressed refractive index.
  • this area of depressed index 82 functions to increase the effective area (A e ff) of the fiber, and helps to differentiate the propagation constants of the spatial modes, and thus reduce mode coupling and the resultant multi-path interference (MPI).
  • the increased effective area (A e ff) translates to reduced non-linear effects.
  • the increase in refractive index at region 84 to 1.4605 is used to guide the LP 0 2 spatial mode, while the depression in index at region 86 is used to control the dispersion slope.
  • the refractive index in region 82 is substantially the same as the refractive index in region 86, and the cladding region 90, although other embodiments can be designed in which they are not substantially the same.
  • the refractive index at region 88 functions to limit the expansion of the LP0 2 spatial mode into the cladding.
  • the profile supports between three and six spatial modes in the transmission bandwidth of approximately 1520 to 1570nm, including the LPoi, LP 02 , P ⁇ and LP21 spatial modes. The calculated characteristics for this profile are:
  • a eff for the LP 02 spatial mode is approximately 94 ⁇ m . Attenuation is about 0.2 - 0.4dB/km.
  • Cut off for the LP 0 2 spatial mode is greater than 1900nm.
  • Dispersion is approximately -2.6ps/nn ⁇ km at 1550nm.
  • Dispersion slope is approximately -0.07ps/nm 2 -km.
  • Dispersion zero is adjustable between 1470 to 1515nm.
  • the calculated bending loss is acceptable with a calculated n eff of 1.4469 for the LP 02 spatial mode.
  • Fig. 10 illustrates the total chromatic dispersion and dispersion slope of the refractive index profile 80 shown in Fig. 9 for a signal in the LP02 spatial mode.
  • the total chromatic dispersion 94 is the sum of the material dispersion 92 and the waveguide dispersion 96.
  • the waveguide dispersion can be modified so as to arrive at the desired dispersion slope and zero dispersion point.
  • a unique feature of the fiber profile 80 of Fig. 9 is the negative slope of the total chromatic dispersion 94, which is approximately -0.07ps/nm 2 -km. It should be appreciated that by adjusting the zero dispersion point, a positive or negative dispersion can be experienced over the transmission wavelength.
  • depression 82 in one embodiment, can be manipulated or dispensed with entirely causing some loss of effective area (A eff ), and increased mode coupling.
  • Fig. 1 la illustrates another fiber profile which exhibits extremely low dispersion slope, with a characteristic bending loss of 1.4452.
  • the area 95 represents a dip at the center which acts to increase the effective area (A e ff) and to reduce multi-path interference (MPI).
  • Area 97 of the fiber profile is an area of increased refractive index of approximately 1.460.
  • the decrease in refractive index at region 98 is used to guide the LP 0 2 spatial mode, while the rise in index at region 99 functions to limit the expansion of the LP 0 2 spatial mode into the cladding.
  • Fig. 1 la is the effective area (A e ff) for the LP0 2 spatial mode is 260 ⁇ m 2 , with a dispersion at 1550nm of 4.35ps/nm-km and a negligible slope of 0.00007ps/nm 2 -km.
  • the fiber profile exhibits an n e f f of 1.4452.
  • Fig. 1 lb illustrates the total chromatic dispersion and dispersion slope of the refractive index profile shown in Fig. 1 la for a signal in the LP02 spatial mode.
  • the total chromatic dispersion 107 is the sum of the material dispersion 105 and the waveguide dispersion 109.
  • the waveguide dispersion can be modified so as to arrive at the desired dispersion slope and zero dispersion point.
  • a unique feature of the fiber profile of Fig. 1 la is the low slope of the total chromatic dispersion 107, which is approximately
  • a fiber with the desired characteristics of dispersion, dispersion slope and effective area (A eff ), may be designed by utilizing a few mode fiber with appropriate characteristics for a desired specific higher order spatial mode, such as the LP 02 spatial mode. While four sample profiles have been shown, it is understood that one skilled in the art could produce a large range of profiles having the desired characteristics based on the principles of the invention. Suitable fibers with positive dispersion or negative dispersion, positive dispersion slope and negative dispersion slope may all be designed for higher order spatial modes without departing from the spirit and scope of the invention.
  • S/N signal-to- noise ratio
  • Some of the noise in the fiber is generated in a different spatial distribution than that of the signal.
  • some of the non-linear noise generated by a signal propagating in the LP 02 spatial mode is distributed in the LPoi spatial mode.
  • this noise has a physical property that differentiates it from the signal. This property can be used to filter the noise out of the signal.
  • Transforming the high order spatial mode (LP02) of the signal into a lower order or fundamental spatial mode (LPoi), and simultaneously transforming any lower order spatial mode energy to a high order spatial mode has the effect of filtering out this noise, when the transformed signal is subsequently carried through a single mode fiber (SMF).
  • SMF single mode fiber
  • any noise which was in the lower order spatial mode is transformed into a higher order spatial mode (higher than the new spatial mode of the signal) and this higher order spatial mode is not supported by the subsequent single mode fiber (SMF).
  • SMF single mode fiber
  • only part of the noise is filtered out in this process and the non-linear noise generated in the same spatial mode as the signal, and other noise components remain. This reduction in the overall noise improves the signal-to-noise ratio, thereby enabling higher transmission capacity or increased bit rate.
  • Fig. 12 illustrates a block diagram of a conventional transmission system 100 known to the prior art.
  • Transmitter 102 is coupled to a span of single-mode fiber (SMF) 104, and SMF 104 is coupled to the input of amplifier 106.
  • the output of amplifier 106 is coupled to SMF 108, and SMF 108 is coupled to the input of amplifier 110.
  • the output of amplifier 110 is coupled to SMF 112, and SMF 112 is coupled to receiver 114.
  • Signal 1 propagates in SMF 104 and Noise 1 is generated during propagation of the signal. As it propagates, the signal intensity is attenuated making it necessary to re-amplify the signal.
  • SMF 104 is coupled to Amplifier 1 (106), which amplifies Signal 1.
  • Amplifier 1 (106) amplifies Noise 1 as well.
  • Signal2, which is the amplified Signall propagates through SMF 108 along with Noise2.
  • Noise2 is the amplified Noise 1 and additional noise generated during propagation.
  • Signal2 and Noise2 are then amplified by Amplified (110), whose output is coupled to SMF 112. SignaB and Noise3 then propagate in SMF 112 to Receiver 114.
  • Fig. 13 illustrates a block diagram of one embodiment of a transmission system 120 according to the present invention.
  • Transmitter 102 is coupled to SMF 104 and to an input of spatial mode transformer 126, and an output of spatial mode transformer 126 is connected to transmission high order mode fiber (THOM) 128.
  • THOM 128 is coupled to an input of spatial mode transformer 130, and an output of spatial mode transformer 130 is coupled to SMF 112, which is coupled to receiver 1 14.
  • Transmitter 102 transmits Signal4 into transformer 126, which may be connected directly to transmitter 102 (not shown), or connected to it by SMF 104 as shown.
  • Transformer 126 which may be of a type described in pending US application 09/248,969 filed on February 12, 1999, converts substantially all of the light to a single higher order spatial mode, such as the LP 02 spatial mode.
  • the output of transformer 126 containing Signal5 primarily in the LP 02 spatial mode and Noise5 which designates the noise component existing in the LPoi spatial mode, propagate into the transmission high-order mode fiber (THOM) 128 of the invention.
  • transmitter 102 may be designed to output the signal directly in the desired high order spatial mode, and thus may be directly coupled to (THOM) 128.
  • the fiber is optimized to support the LP02 spatial mode, and during transmission, noise is generated, some of which is generated in the LPoi spatial mode.
  • THOM 128 which is designed according to an embodiment of the current invention, contains a large effective area (A e ff) for signals in the LP 02 spatial modes, and thus can support a higher intensity signal without experiencing non-linear effects. This allows the propagation distance of Signal5 to be substantially greater before re-amplification is necessary. Note that Noise5 is propagating with Signal5.
  • THOM 128 is coupled to spatial mode transformer 130, which, in one embodiment, is a spatial mode transformer which transforms both the LPoi spatial mode to the LP 0 2 spatial mode, as well as any noise in the LPoi spatial mode to the LP 02 spatial mode.
  • Spatial mode transformer 130 converts substantially all of Signal5 from the LP 02 spatial mode to the fundamental LP 0 ⁇ spatial mode for transmission into SMF 112 as Signal ⁇ , while simultaneously converting any noise which was received in the LPoi spatial mode to a higher order spatial mode as Noise ⁇ .
  • Signal ⁇ and Noise ⁇ propagate into SMF 112 which is designed to support only the LP 0 ⁇ spatial mode, thus attenuating Noise6.
  • SMF 112 is connected to receiver 114 which will receive Signal ⁇ with reduced noise due to the absence of noise component Noise ⁇ , although other noise components (not shown) exist.
  • transformer 130 may be designed to attenuate or block any energy received in the LPoi spatial mode, and transformer 130 may output its signal directly to receiver 114 without requiring SMF 112 (not shown).
  • Fig. 14 illustrates a block diagram of another embodiment of a transmission system 140 according to the present invention.
  • Transmitter 102 is coupled to SMF 104, and SMF 104 is coupled to an input of spatial mode transformer 126.
  • An output of spatial mode transformer 126 is coupled to THOM 128, and THOM 128 is coupled to the input of amplifier 150.
  • the output of amplifier 150 is coupled to THOM 152, and THOM 152 is coupled to an input of spatial mode transformer 130.
  • An output of spatial mode transformer 130 is connected to SMF 112, and SMF 112 is connected to receiver 114.
  • Transmitter 102 injects a high intensity signal, designated as Signal7 into SMF 104 which is connected to spatial mode transformer 126.
  • transmitter 102 may be directly connected to spatial mode transformer 126.
  • transmitter 102 may be designed to output its signal directly in the desired high order spatial mode, and thus transmitter 102 may be directly connected to THOM 128.
  • the output of spatial mode transformer 126 which, as described above, converts substantially all of the signal to a single high order mode, is connected to THOM 128.
  • THOM 128 transmits Signal ⁇ in the LP 02 spatial mode as well as noise, some of which is in the LPoi spatial mode and is designated as Noise ⁇ .
  • THOM 128 is connected to amplifier 150, which may be an Erbium Doped Fiber Amplifier (EDFA) that is designed to support the LP 02 spatial mode.
  • amplifier 150 may contain a standard
  • EDFA which only supports the LPoi spatial mode, a spatial mode transformer at the input stage, and a spatial mode transformer at the output stage.
  • the signal can be converted to the fundamental spatial mode for amplification and then back to the higher order spatial mode prior to propagating into THOM 152.
  • Amplifier 150 may be a single or multiple stage amplifier, and may contain dispersion compensation, and/or add/drop components.
  • the amplified signal may be a high intensity signal due to the large effective area (A eff ) of THOM
  • the amplified signal designated Signal9 is in the LP02 spatial mode, and contains amplified Noise9 which is substantially in the LPoi spatial mode. These propagate in THOM 152.
  • THOM 152 is connected to spatial mode transformer 130, which simultaneously transforms both the LP 02 spatial mode of Signal9 to the LPoi spatial mode, and the LPoi spatial mode of Noise9 to the LP 02 spatial mode.
  • Spatial mode transformer 130 converts substantially all of Signal9 from the LP 02 spatial mode to the fundamental LPoi spatial mode for transmission into SMF 112, while simultaneously converting Noise9 which was received in the LPoi spatial mode to a higher order spatial mode.
  • SMF 112 which is designed to support only the LPoi spatial mode, thus attenuating Noise 10.
  • SMF 112 is connected to receiver 114 which receives Signal 10 with reduced noise due to the absence of noise component Noise 10.
  • spatial mode transformer 130 may be designed to attenuate or block any energy received in the LPoi spatial mode (not shown), and transformer 130 may output its signal directly to receiver 114 without requiring SMF 1 12 (not shown).
  • the total chromatic dispersion of THOM 152 may be designed to counterbalance the total chromatic dispersion experienced by the signal in THOM 128, such that the system 140 experiences minimal total dispersion without a dedicated dispersion compensating fiber.
  • the length of SMF 112 may be chosen so as to compensate for the dispersion introduced by THOM 128 and THOM 152.
  • Dashed line 159 indicates the repeating block that may be utilized to build a larger and more complex system, where the end of SMF 112 may be connected to another repeating block at input to spatial mode transformer 126.
  • Fig. 15 illustrates a system 160 which utilizes an inventive fiber of Fig. 9 to achieve a substantially dispersion free transmission system.
  • Transmitter 102 is coupled to SMF 104, and
  • SMF 104 is coupled to an input of spatial mode transformer 126.
  • An output of spatial mode transformer 126 is coupled to THOM 172, and THOM 172 is coupled to the input of spatial mode transformer 130.
  • An output of spatial mode transformer 130 is connected to SMF 112, and SMF 112 is connected to receiver 114.
  • Transmitter 102 injects a signal, designated as Signall 1 a short length of SMF 104 over which no substantial dispersion occurs, and which is connected to spatial mode transformer 126.
  • transmitter 102 may be directly connected to spatial mode transformer 126.
  • transmitter 102 may be designed to output its signal directly in the desired high order spatial mode, and thus transmitter 102 may be directly connected to THOM 172.
  • THOM 172 is designed according the principles explained above, and its profile is similar to that shown in Fig. 9, with a dispersion of -2.6ps/nm-km and a dispersion slope of -0.07ps/nm -km.
  • THOM 172 transmits the output of spatial mode transformer 126, designated Signal 12 which is substantially in the high order spatial mode.
  • THOM 172 is connected to spatial mode converter 130, which converts Signal 12 from the high order spatial mode to the fundamental LPoi spatial mode prior to outputting the signal as Signal 13 to SMF 112.
  • SMF 112 is designed to counterbalance the dispersion and dispersion slope of the signal encountered over THOM 172, prior to the arrival of Signal 13 at receiver 114.
  • Signal 13 is received with substantially zero chromatic dispersion, yet having experienced large local dispersion in each section of its travel.
  • Dashed line 180 indicates the repeating block that may be utilized to build a larger and more complex system, where the end of SMF 112 may be connected to another repeating block at input to spatial mode transformer 126.
  • THOM 172 may contain a 50 kilometer span of THOM, which has a characteristic dispersion of -2.6ps/nm-km, and slope of -0.07ps/nm km.
  • SMF 112 may contain a 50 kilometer length of standard SMF such as LEAF® by Corning Incorporated, Corning, New York, with dispersion of 2.6ps/nnrkm, and a slope of 0.07ps/nm 2 -km.
  • several lengths of THOM may be designed, such that the sum of the dispersion and slope experienced by a signal may be compensated by a single SMF span.
  • Fig. 16 illustrates the resultant effective dispersion in ps/nm over the length of the system 160 from transformer 126 to receiver 114.
  • THOM 128 and THOM 172 is exactly compensated by SMF 112.
  • spatial mode transformers 126 and 130 may contain amplifiers or other components not shown

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

L'invention concerne des procédés et des dispositifs permettant de transmettre un signal optique à énergie optique. Selon une variante, le système comprend au moins une liaison de transmission à guide d'ondes optique, cette liaison transmettant sensiblement l'ensemble de l'énergie optique suivant un mode spatial unique d'ordre élevé. Selon une variante, le guide d'ondes optique présente une certaine dispersion et une certaine pente de dispersion pour une largeur de bande de transmission donnée. Selon une autre variante, l'invention concerne un système de transmission optique qui comprend une unité de transformation de mode spatial positionnée pour recevoir un signal optique. Cette unité transforme l'énergie optique du signal optique d'un mode spatial d'ordre peu élevé en mode spatial d'ordre élevé. Le système comprend en outre un guide d'ondes de transmission optique relié optique à une unité de transformation de mode spatial, et ce guide d'ondes de transmission transmet sensiblement toute l'énergie optique dans le mode spatial d'ordre élevé. Selon un autre aspect, l'invention concerne un procédé de transmission de signal optique dont l'énergie est sensiblement en mode spatial unique d'ordre élevé. Le procédé consiste à recevoir le signal optique à énergie optique dans le mode spatial unique d'ordre élevé, et à transmettre ce signal sur une liaison de transmission, laquelle comprend un guide d'ondes optique.
PCT/US2000/004528 1999-02-23 2000-02-23 Systeme de transmission a mode spatial d'ordre eleve WO2000051268A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU32401/00A AU3240100A (en) 1999-02-23 2000-02-23 High order spatial mode transmission system

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US12132199P 1999-02-23 1999-02-23
US60/121,321 1999-02-23
US09/510,027 2000-02-22
US09/510,027 US6418256B1 (en) 1999-02-23 2000-02-22 High order spatial mode optical fiber
US09/507,001 2000-02-22
US09/507,001 US6360045B1 (en) 1999-02-23 2000-02-22 High order spatial mode transmission system

Publications (2)

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WO2000051268A1 true WO2000051268A1 (fr) 2000-08-31
WO2000051268B1 WO2000051268B1 (fr) 2000-11-23

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PCT/US2000/004528 WO2000051268A1 (fr) 1999-02-23 2000-02-23 Systeme de transmission a mode spatial d'ordre eleve

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US6563981B2 (en) 2001-01-31 2003-05-13 Omniguide Communications Electromagnetic mode conversion in photonic crystal multimode waveguides
US6603911B2 (en) 1998-10-14 2003-08-05 Massachusetts Institute Of Technology Omnidirectional multilayer device for enhanced optical waveguiding
US6625364B2 (en) 2001-01-25 2003-09-23 Omniguide Communications Low-loss photonic crystal waveguide having large core radius
FR2860598A1 (fr) * 2003-10-03 2005-04-08 Cit Alcatel Supression de mode(s) de propagation de signaux indesirables en aval d'un convertisseur de mode
US6895154B2 (en) 2001-01-25 2005-05-17 Omniguide Communications Photonic crystal optical waveguides having tailored dispersion profiles
FR2864254A1 (fr) * 2003-12-23 2005-06-24 Cit Alcatel Fibre optique multimode hom a gestion de dispersion
US6990282B2 (en) 1999-12-10 2006-01-24 Crystal Fibre A/S Photonic crystal fibers
EP1764634A1 (fr) * 2005-09-20 2007-03-21 Draka Comteq B.V. Fibre de compensation de la dispersion chromatique et de la pente de dispersion cumulées

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FR2839221B1 (fr) * 2002-04-29 2006-01-27 Cit Alcatel Fibre de compensation de la dispersion chromatique cumulee dans une fibre a dispersion chromatique negative
US7228029B1 (en) * 2005-09-20 2007-06-05 Furukawa Electric North America Inc. Short pulse lasers using large mode area fibers and higher order modes
US7356232B1 (en) * 2006-08-01 2008-04-08 Furukawa Electric North America Optical fibers for high power applications
JP5805196B2 (ja) * 2010-09-03 2015-11-04 オーエフエス ファイテル，エルエルシー 分散補償システム、および改善された性能指数を有する分散補償ファイバ

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6603911B2 (en) 1998-10-14 2003-08-05 Massachusetts Institute Of Technology Omnidirectional multilayer device for enhanced optical waveguiding
US6990282B2 (en) 1999-12-10 2006-01-24 Crystal Fibre A/S Photonic crystal fibers
US6625364B2 (en) 2001-01-25 2003-09-23 Omniguide Communications Low-loss photonic crystal waveguide having large core radius
US6895154B2 (en) 2001-01-25 2005-05-17 Omniguide Communications Photonic crystal optical waveguides having tailored dispersion profiles
US7072553B2 (en) 2001-01-25 2006-07-04 Omniguide Communications Low-loss photonic crystal waveguide having large core radius
US6728439B2 (en) 2001-01-31 2004-04-27 Omniguide Communications Electromagnetic mode conversion in photonic crystal multimode waveguides
US6563981B2 (en) 2001-01-31 2003-05-13 Omniguide Communications Electromagnetic mode conversion in photonic crystal multimode waveguides
CN100405102C (zh) * 2003-10-03 2008-07-23 德雷卡通信技术公司 抑制模式转换器下游的不需要的信号传播模式
FR2860598A1 (fr) * 2003-10-03 2005-04-08 Cit Alcatel Supression de mode(s) de propagation de signaux indesirables en aval d'un convertisseur de mode
WO2005036223A1 (fr) * 2003-10-03 2005-04-21 Draka Comteq Bv Suppression de mode(s) de propagation de signal indesirable en aval d'un convertisseur de mode
US7724995B2 (en) 2003-10-03 2010-05-25 Draka Comteq B.V. Suppresson of undesirable signal propagation mode(s) downstream of mode converter
EP1548961A1 (fr) * 2003-12-23 2005-06-29 Draka Comteq B.V. Fibre optique multimode HOM à gestion de dispersion
US7272286B2 (en) 2003-12-23 2007-09-18 Draka Comteq B.V. Dispersion managed HOM multimode optical fibre
CN100374887C (zh) * 2003-12-23 2008-03-12 德雷卡通信技术公司 色散受控的高阶模多模光纤
FR2864254A1 (fr) * 2003-12-23 2005-06-24 Cit Alcatel Fibre optique multimode hom a gestion de dispersion
FR2891058A1 (fr) * 2005-09-20 2007-03-23 Draka Comteq France Fibre de composation de la dispersion chromatique et de la pente de dispersion cumulees.
EP1764634A1 (fr) * 2005-09-20 2007-03-21 Draka Comteq B.V. Fibre de compensation de la dispersion chromatique et de la pente de dispersion cumulées
US7440662B2 (en) 2005-09-20 2008-10-21 Draka Comteq B.V. Compensating fiber for cumulated chromatic dispersion and chromatic dispersion slope

Also Published As

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WO2000051268B1 (fr) 2000-11-23
AU3240100A (en) 2000-09-14
WO2000051269A1 (fr) 2000-08-31
WO2000051269A8 (fr) 2001-04-12
WO2000051269A9 (fr) 2001-11-22
WO2000051269B1 (fr) 2000-11-16

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