CN113938201A

CN113938201A - Optical fiber network

Info

Publication number: CN113938201A
Application number: CN202111095927.4A
Authority: CN
Inventors: 王兵; 陈浩; 叶汉; 刘为为; 秦承志; 陆培祥
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2022-01-14
Anticipated expiration: 2041-09-18
Also published as: CN113938201B

Abstract

The invention discloses an optical fiber network, and belongs to the field of optics. The method comprises the following steps: the input end of the first optical coupler is connected with one end of a first optical fiber, the coupling end is connected with one end of a fourth optical fiber, the straight-through end is connected with one end of a second optical fiber, and the isolation end is connected with one end of a third optical fiber; the input end of the second optical coupler is connected with the other end of the second optical fiber, the coupling end is connected with the other end of the third optical fiber, the straight-through end is connected with the other end of the first optical fiber, and the isolation end is connected with the other end of the fourth optical fiber; the length difference between the first optical fiber and the third optical fiber and the length difference between the second optical fiber and the fourth optical fiber are 0; the length difference between the first optical fiber and the second optical fiber and between the fourth optical fiber and the third optical fiber satisfies the following conditions: 1) the two length differences are equal to positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 2 times the width of the incident pulse. The invention adjusts the structure of the optical fiber network, realizes lattice structures of different forms, and analyzes and regulates the evolution of the pulse in the system by combining the lattice characteristics and the evolution equation.

Description

Optical fiber network

Technical Field

The invention belongs to the field of micro-nano optics, and particularly relates to an optical fiber network.

Background

The development of new artificial structures and materials is one of the main research topics in today's optical field. In most studies to date, such structures achieve photonic modulation mainly by manipulating the spatial distribution of refractive index, where the typical structure is a photonic lattice. Time is a basic degree of freedom of photons, the distribution of the photons on the time dimension is regulated, the method has important application in the technologies of signal transmission, storage, processing and the like, and meanwhile, the time division multiplexing technology can also be used for increasing the optical communication capacity. The space photon lattice concept is popularized to the time dimension to form the time domain photon lattice, the energy band theory can be applied to the regulation and control of photons, and the transportation of the photons can be controlled in a more flexible and controllable mode. At present, the research on two-dimensional time domain photonic lattices is in an exploration stage, and the realization method mainly utilizes an optical fiber loop.

Using fiber optic networks, researchers studied nonlinear properties (a.l.m.muniz, sci.rep.9, 9518(2019)) and soliton transport (a.l.m.muniz, phys.rev.lett.123, 253903(2019)) in a two-dimensional time domain photonic lattice. However, the optical fiber network in the above work is only suitable for constructing the evolution of the rectangular time domain photonic lattice control pulse, and how to realize two-dimensional time domain photonic lattices with different structures is one of the subjects that need to be researched at present.

Disclosure of Invention

In view of the shortcomings and needs of the prior art, the present invention provides a fiber optic network that aims at flexibly regulating the evolution of pulse amplitude by constructing two-dimensional time-domain photonic lattices with different structures to control the coupling process of pulses within the system.

To achieve the above object, according to a first aspect of the present invention, there is provided an optical fiber network comprising: a first optical fiber, a second optical fiber, a third optical fiber, a fourth optical fiber, a first optical coupler and a second optical coupler;

the input end of the first optical coupler is connected with one end of a first optical fiber, the coupling end is connected with one end of a fourth optical fiber, the straight-through end is connected with one end of a second optical fiber, and the isolation end is connected with one end of a third optical fiber;

the input end of the second optical coupler is connected with the other end of the second optical fiber, the coupling end is connected with the other end of the third optical fiber, the straight-through end is connected with the other end of the first optical fiber, and the isolation end is connected with the other end of the fourth optical fiber;

the length difference between the first optical fiber and the third optical fiber is 0, and the length difference between the second optical fiber and the fourth optical fiber is 0; the length difference between the first optical fiber and the second optical fiber and the length difference between the fourth optical fiber and the third optical fiber satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 2 times the width of the incident pulse.

Preferably, the evolution of pulses in the network with the number L of cycle turns follows the following coupled mode equation:

idA_m/dL-K_n(A_n-1+A_m+1)＝0

wherein i is an imaginary unit, d is a derivative symbol, A_mFor the complex amplitude of the m-th pulse, the subscript m denotes the number of pulses in the pulse sequence on the time axis, A₀The time difference between each pulse is determined by the length difference between the first and second optical fibers and the length difference between the fourth and third optical fibers for the complex amplitude of the incident pulse, K_msinC is the coupling strength between adjacent pulses and is determined by the optical coupler splitting ratio C.

Has the advantages that: aiming at the problem that in the prior art of realizing pulse multiplexing by using an optical fiber loop, the generation of a pulse sequence is only based on the simple superposition of pulses in the optical fiber loop, the invention combines the optical fiber network and condensed state physics, adopts the concept of mode coupling in one-dimensional photonic crystal lattices to analyze the evolution of the pulses in a system, provides a more feasible theoretical analysis method for regulating and controlling the pulses, and realizes the feasible and more specific method for controlling and controlling the regulated and controlled pulses.

To achieve the above object, according to a second aspect of the present invention, there is provided an optical fiber network comprising: the optical fiber comprises a first optical fiber, a second optical fiber, a third optical fiber, a fourth optical fiber, a first optical coupler, a second optical coupler, a third optical coupler, a fifth optical fiber and a sixth optical fiber;

the input end of the first optical coupler is connected with one end of a first optical fiber, the coupling end is connected with one end of a fourth optical fiber, the straight-through end is connected with one end of a fifth optical fiber, and the isolation end is connected with one end of a sixth optical fiber;

the input end of the third optical coupler is connected with the other end of the fifth optical fiber, the coupling end is connected with the other end of the sixth optical fiber, the straight-through end is connected with one end of the second optical fiber, and the isolation end is connected with one end of the third optical fiber;

the length difference between the first optical fiber and the third optical fiber is 0, the length difference between the second optical fiber and the fourth optical fiber is 0, the length difference between the fifth optical fiber and the sixth optical fiber is positive, and the two pulse wave packets are not overlapped; the length difference between the first optical fiber and the second optical fiber and the length difference between the fourth optical fiber and the third optical fiber satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times the width of the incident pulse.

Has the advantages that: aiming at the problems of single regulation and control means and modulation dimension, low time duty ratio, low pulse multiplexing flexibility and the like in the existing technology for realizing pulse regulation and evolution by relying on an optical fiber loop, the invention combines a classical honeycomb lattice model in condensed state physics with time domain optics, pulses are discretely coupled under the action of optical fiber internal transmission and an optical coupler in an optical fiber network system, the coupling process can be analyzed by depending on a mature theory and further reversely regulate and control the pulse multiplexing process, the technology not only increases the operability of pulse evolution regulation and control, but also further expands the application scene of time domain optics.

idA/dL-(K₁B_r1+K₂B_r2+K₃B_r3)＝0

wherein i is an imaginary unit, d is a derivative symbol, A, B is used for representing a lattice point corresponding to the moment of the pulse, and K₁、K₂And K₃The coupling coefficient indicating the inter-lattice pulse energy is determined by the splitting ratio of the first optical coupler, the second optical coupler, and the third optical coupler, and subscripts r1, r2, and r3 indicate the vector direction of the inter-lattice coupling.

To achieve the above object, according to a third aspect of the present invention, there is provided an optical fiber network comprising: the optical fiber comprises a first optical fiber, a second optical fiber, a third optical fiber, a fourth optical fiber, a first optical coupler, a second optical coupler, a third optical coupler, a fourth optical coupler, a fifth optical fiber, a sixth optical fiber, a seventh optical fiber and an eighth optical fiber;

the input end of the second optical coupler is connected with the other end of the second optical fiber, the coupling end is connected with the other end of the third optical fiber, the straight-through end is connected with one end of the seventh optical fiber, and the isolation end is connected with one end of the eighth optical fiber;

the input end of the fourth optical coupler is connected with the other end of the seventh optical fiber, the coupling end is connected with the other end of the eighth optical fiber, the straight-through end is connected with the other end of the first optical fiber, and the isolation end is connected with the other end of the fourth optical fiber;

the length difference between the first optical fiber and the third optical fiber is 0, and the length difference between the second optical fiber and the fourth optical fiber is 0; the length difference between the first optical fiber and the second optical fiber and the length difference between the fourth optical fiber and the third optical fiber need to satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times the width of the incident pulse;

the length difference between the fifth optical fiber and the sixth optical fiber and the length difference between the seventh optical fiber and the eighth optical fiber satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that two adjacent pulse wave packets are not overlapped.

idA_m,n/dL-K₁A_m-1,n-1-K₂A_m+1,n-1-K₃A_m-1,n+1-K₄A_m+1,n+1＝0

wherein i is an imaginary symbol, idA_m,nthe/dL represents the pulse amplitude A at (m, n) coordinates in a two-dimensional plane_m,nDifferential of number of evolution turns, K₁、K₂、K₃And K₄The coupling coefficient representing the inter-lattice pulse energy depends on the splitting ratios of the first, second, third and fourth optical couplers.

Has the advantages that: the invention realizes the mutual coupling of the pulse and 4 fixed pulses in the network once in each circulation by adding the optical coupler and the short optical fibers with different lengths and utilizing the time delay introduced by the length difference of the optical fibers and the light splitting effect of the coupler, and the coupling effect can be combined with the centromere rectangular lattice in the condensed state physics to analyze the pulse coupling process and further control the pulse evolution, thereby establishing an exact theoretical technology for the evolution of the pulse in the optical fiber network and realizing the effectiveness and the operability of pulse multiplexing.

To achieve the above object, according to a fourth aspect of the present invention, there is provided an optical fiber network including: the optical fiber comprises a first optical fiber, a second optical fiber, a third optical fiber, a fourth optical fiber, a first optical coupler, a second optical coupler, a first phase modulator and a second phase modulator;

the input end of the second optical coupler is connected with one end of the first optical fiber, the coupling end is connected with one end of the fourth optical fiber, the straight-through end is connected with one end of the second optical fiber, and the isolation end is connected with one end of the third optical fiber;

the first optical fiber is connected with a first phase modulator, and the fourth optical fiber is connected with a second phase modulator;

the length difference between the first optical fiber and the third optical fiber is 0, and the length difference between the second optical fiber and the fourth optical fiber is 0; the length difference between the first optical fiber and the second optical fiber and the length difference between the fourth optical fiber and the third optical fiber satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times of the phase modulation period.

idA_m,n/dL-[K_m(A_m-1,n+A_m+1,n)+K_n(A_m,n-1+A_m,n+1)]＝0

wherein, idA_m,nthe/dL represents the pulse amplitude A at (m, n) coordinates in a two-dimensional plane_m,nDifferential of number of evolution turns, K_mAnd K_nThe coupling strength of the pulse in the lattice along the m direction and the n direction is respectively regulated and controlled by the modulation amplitude of the phase modulator and the splitting ratio of the second optical coupler and the third optical coupler.

Preferably, the first to fourth optical fibers are single mode optical fibers in which a dispersion compensating fiber is indirectly provided.

Has the advantages that: aiming at the problems that pulse broadening is caused by secondary dispersion when pulses are transmitted in an optical fiber network, and the overlapping occurs between the pulses to cause signal transmission quality, the invention provides negative secondary dispersion by adding a dispersion compensation fiber in the optical fiber network to inhibit the pulse broadening and realize the effective coupling and transmission of the pulses in the optical fiber network.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:

(1) aiming at the problems that in the prior time division multiplexing and other technologies, pulse repetition frequency is firstly modulated by an electric signal, the multiplexing of optical fiber single-ring structure pulses is limited by the length of an optical fiber ring and the like, the invention provides an optical fiber network.

(2) Aiming at the problems of single regulation and control means and modulation dimension, low time duty ratio, low pulse multiplexing flexibility and the like in the existing technology for realizing pulse regulation and control and evolution by relying on an optical fiber loop, the invention provides an optical fiber network, wherein the pulse regulation and control dimension can be increased by changing the number of optical couplers and optical fiber sections in the optical fiber network, namely, in the time dimension, each pulse is coupled with 3 pulses with a certain time interval in the couplers, the pulse multiplexing controllability and flexibility are expanded, and a richer pulse regulation and control scheme is realized.

(3) Aiming at the problems that the traditional technologies such as time division multiplexing, pulse frequency multiplication and the like are limited by the modulation frequency of an electric signal and the electrical limitation of pulses can be effectively realized by using an optical fiber network system, the invention provides an optical fiber network, wherein the optical fiber network is constructed by using 6 sections of optical fibers and 4 optical couplers, and energy mutual coupling between each pulse and 4 pulses with fixed time intervals is realized by using the time delay difference introduced by the length difference of the optical fibers and the light splitting action of the couplers, so that the pulse evolution is regulated, the continuous coupling and dispersion of the pulses in the transmission process are realized, the number of the pulses in the network is continuously expanded, and the effective regulation and control of the pulses are realized.

(4) Aiming at the problems of single pulse multiplexing and coupling regulation and control technical mode, low flexibility and the like, the invention provides an optical fiber network, which combines a phase modulator, a dispersion optical fiber and the optical fiber network, effectively modulates a pulse spectrum and a time domain waveform due to effective combination of periodic phase modulation and secondary dispersion, realizes coupling between pulses of adjacent modulation periods in a time domain dimension, realizes effective dispersion of the pulses by a novel means, and simultaneously can realize the coupling effect between the pulses and 4 pulses with specific time intervals by combining the optical fiber network, realize effective coupling of energy between the pulses and further expand a pulse multiplexing method.

Drawings

FIG. 1(a) is a schematic diagram of a first fiber optic network architecture provided in the present invention;

FIG. 1(b) is a schematic diagram of a second fiber optic network architecture provided in the present invention;

FIG. 1(c) is a schematic diagram of a third fiber optic network architecture provided in the present invention;

FIG. 1(d) is a schematic diagram of a fourth fiber optic network architecture provided in the present invention;

FIG. 2 is a schematic diagram of the evolution of a single optical pulse in the optical fiber network of FIG. 1(a) according to the present invention;

FIG. 3 is a schematic diagram of the distribution of pulses in the loop of the present invention under the action of the couplers 3, 5 and the delay δ t of FIG. 1 (b);

FIG. 4 is a schematic diagram of a cellular time domain photonic lattice structure constructed from the network shown in FIG. 1(b) in accordance with the present invention;

FIG. 5 is a schematic diagram of the distribution of pulses in the network of FIG. 1(b) according to the present invention;

FIG. 6 is a schematic view of a rectangular centromere photonic lattice structure constructed from the network shown in FIG. 1(c) in accordance with the present invention;

FIG. 7 is a schematic diagram of the pulse distribution of the pulses in the network of FIG. 1(d) according to the present invention;

fig. 8 is a schematic diagram of a rectangular photonic time domain lattice structure constructed in the network shown in fig. 1(d) according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention adjusts the structure of the optical fiber network, can further realize lattice structures of different forms, and combines lattice characteristics and an evolution equation to analyze and regulate the evolution of the pulse in the system; the evolution characteristic of the transmission of the pulse in the network can be further flexibly regulated and controlled by the splitting ratio of the coupler and the phase modulation depth.

Specifically, an optical fiber network is built by combining an optical fiber and an optical coupler, and the length of the optical fiber is adjusted to introduce time delay to construct a one-dimensional time domain photon lattice structure; by adding new optical fibers and couplers, the coupling relation between pulses is further expanded, and the constructed time domain photonic crystal lattice is popularized from one dimension to two dimensions; based on a two-dimensional lattice structure, the lattice structure in solid physics is combined with an optical fiber network and a time dimension to construct a two-dimensional time domain photonic lattice comprising a honeycomb type, a rectangular centromere, a rectangular and a square two-dimensional time domain photonic lattice, so that a new mode is provided for researching and regulating pulse evolution.

The invention provides a method for regulating pulse coupling and evolution of an optical fiber network, which comprises the following steps:

the optical fiber network is constructed by 4 sections of optical fibers and 2 multiplied by 2 optical couplers, namely, the two sections of optical fibers are connected with the other two sections of optical fibers through the optical couplers as input ends, the optical fibers are connected through the other optical coupler to form a left optical fiber loop and a right optical fiber loop, and optical pulses circulate in the loops in clockwise and counterclockwise directions respectively.

The length difference between the optical fibers enables the transmission time required by the optical pulse to be different, so that the time delay difference delta T is introduced to enable the pulses with the time difference delta T in the left loop and the right loop to simultaneously enter the optical coupler for interaction.

An optical coupler and a pair of short optical fibers with the transmission time difference delta t are added in the network, so that pulses with the difference delta t in the left loop and the right loop can enter the coupler simultaneously; addition period of T_MCan cause a separation T in the same loop_MIs coupled, with a period delta T or T being constructed equivalently by the method_MAnd the dimension in which the lattice is located is named n-direction.

Delay differences Δ T and δ T or T_MThe combination of (1) can combine time domain optics with condensed state physics, and construct a two-dimensional time domain photonic lattice in an m-n plane, so as to analyze and regulate the coupling and evolution of pulses in a network.

The optical pulses in the left and right loops interact in the coupler and cause a change in energy, and the time for the pulses to enter the coupler depends on the length of the fiber, i.e., is determined by the delay differences Δ T and δ T.

To build a lattice in the m direction, it is necessary to pass the pulse through 4 segments of fiber in the network for a time t₁、t₂、t₃And t₄The conditions are satisfied: t is t₁＝t₃＞t₂＝t₄，t₁-t₂＝t₃-t₄When the index is equal to delta T, the subscript is the serial number of the optical fiber, and T is in the loop at the left side of the network under the action of the time delay difference delta T₀Time pulse and right loop t₀The at pulses enter the coupler simultaneously and interact.

When a time domain lattice in the m direction is constructed by the time delay delta T and the coupler, a dispersion compensation fiber is adopted in the fiber network to counteract the dispersion broadening of pulses in the dispersion fiber.

Adding 1 optical coupler and a pair of short optical fibers with transmission time difference delta t on the basis of 4 sections of long optical fibers and 2 multiplied by 2 optical couplers, and enabling t to be in a left loop₀Time of day and right side t₀Pulses enter the coupler at the moment of +/-deltat simultaneously to interact.

Adding phase modulation and fiber dispersion with period of TM in optical fiber network can modulate spectral envelope and time domain waveform of optical pulse respectively to cause interval T in network_MThe pulses of (a) are coupled in the optical fiber.

The evolution of the pulse in the optical fiber network mainly depends on the structure of the two-dimensional time domain photonic lattice constructed by the optical fiber network, namely according to the time delay differences delta T and delta T and the modulation signal T_MThe pulses on the one-dimensional time axis are mapped onto a two-dimensional plane for analysis.

The lattice structure includes but is not limited to: honeycomb lattice, rectangular centroidal lattice, rectangular lattice and tetragonal lattice.

When constructing the honeycomb lattice, the pulse is made to pass through long optical fiber and optical coupler and then through short optical fiber with length difference deltat and one additional coupler to make t in the left loop₀Time pulse is in the network and right loop t₀And t₀Pulses enter the coupler at the +/-deltat moment to interact;

when constructing a rectangular and centered lattice, it is necessary toA group of short optical fibers with the length difference delta t and a coupler are added behind the original 2 couplers in the network respectively, so that the pulse at the time of the loop t0 on the left side and the pulse on the right side t₀T and t₀The + delta T +/-delta T pulses are coupled;

when constructing rectangular and tetragonal lattice, on the basis of 4 sections of long optical fibers and 2X 2 optical couplers, the same phase modulator and long optical fibers are respectively added to the left loop and the right loop to realize t-shaped optical fiber in the left loop and the right loop₀Time pulse and t in same loop₀±T_MCoupling between pulses.

Constructing an equivalent two-dimensional time domain photonic lattice in a one-dimensional time axis by making Delta T far larger than delta T and T_M(ii) a To avoid crosstalk between pulses, the pulse width should also be less than the times deltat and T_M。

The interaction intensity between the pulses can be flexibly regulated and controlled by changing the phase modulation depth and the light splitting ratio of the optical coupler, the modulation depth depends on the intensity of a radio frequency signal loaded on the phase modulator, and the light splitting ratio is determined by the coupling distance in the coupler;

in order to fit with a two-dimensional lattice model, the energy difference of optical pulses among couplers needs to be ensured to be small, namely the splitting ratio and the phase modulation depth of the couplers are required to be not too large and need to be respectively less than 10% and 0.6, and the single-mode optical fiber matched with the phase modulator provides about 600ps²The amount of dispersion.

Besides the optical fiber, coupler and phase modulator needed in the optical fiber network, it also includes: a 1550nm laser, an intensity modulator, a polarization controller, an optical delay line, an erbium-doped optical fiber amplifier, an optical power device, a photodiode, a real-time oscilloscope, a phase modulator and an optical fiber;

the laser and intensity modulator are used for generating light pulses with specific time intervals; the polarization controller is used for adjusting the polarization state of the light pulse; the optical delay line is used for fine adjustment of the length of the optical fiber and the transmission time, the erbium-doped optical fiber amplifier is used for compensating loss in a network, and the photodiode and the real-time oscilloscope record the pulse evolution process.

Example one

Optical fiber network tunerThe method for controlling pulse coupling and evolution is realized by constructing a one-dimensional photon time domain lattice by means of an optical fiber network. As shown in FIG. 1(a),

optical fibers

1, 2, 3, 4 are connected by 2X 2

couplers

7 and 8 to form an optical fiber network including a left loop and a right loop, an incident pulse circulates in the loops in a clockwise direction and a counterclockwise direction, respectively, and a time required for an optical pulse to pass through each optical fiber is t₁、t₂、t₃And t₄And satisfies the condition t₁＝t₃，t₂＝t₄，t₂–t₁＝t₄–t₃Δ T, i.e. the time required for a pulse to pass through each fiber, there is a time delay Δ T. And the time delay is utilized to regulate and control the time of the pulse entering the coupler, so that the coupling between the pulses at different moments is realized.

The evolution of a single pulse within a fiber optic network in an embodiment of the present invention will be further described with reference to fig. 1(a) and 2:

(1) the left loop of the optical fiber network contains a single pulse a, and the pulse a transmits time t in the single-mode optical fiber 1₁The fiber enters a coupler 7, energy is distributed in a right loop in the coupler, and a pulse b is generated and enters the fiber 3;

(2) since the length of the optical fiber 2 is greater than that of the optical fiber 3, the time for the pulse to pass through the

optical fibers

2 and 3 satisfies t₂–t₃Δ T, i.e. the lapse of time T₃The rear pulse b reaches the coupler 8 first, and the energy is distributed to generate a pulse c which enters the optical fiber 1; then the pulse a enters the coupler 8 through the delta T pulse to generate a pulse d entering the optical fiber 4, and the time difference between the pulses c and a and the time difference between the pulses d and b are delta T;

(3) the pulses c and d are transmitted in turn in the

optical fibres

4 and 1 for a time t₄And t₁Sequentially entering a coupler 7, and generating pulses e and f in a right loop and a left loop respectively;

(4) since the pulse satisfies t at the time of passing through the optical fiber₁+t₂＝t₃+t₄The relationship of the interaction occurring in the coupler during the pulse cycle is kept constant, for example: during the cycle, pulse a always meets pulses b and d to exchange energy in

couplers

7 and 8; at the same time, new light pulse increases with the number of cyclesIs generated continuously, and the interval of the pulse keeps the delta T unchanged.

Specifically, to cancel the dispersion-induced broadening of the pulse during cycling, dispersion compensating fibers 5 and 6 are added to the single-

mode fibers

1 and 4 to compensate for the amount of dispersion in the single-mode fibers.

Selecting optical fibers with specific length to build an optical fiber network, and combining an optical coupler to realize t in a left loop in the network₀Pulse at time and right loop t₀And t₀-coupling between pulses at time at. Further, the pulses in the two loops are arranged in a row: will be right side loop inner t₀And t₀The pulse being placed in the left loop T at time- Δ T₀The upper and lower sides of the temporal pulse, i.e. the evolving pulses in fig. 2, are arranged in the order of f, d, a, b, c, e, thereby equivalently constructing a one-dimensional time-domain photonic lattice. Further naming the pulse as A_mM is the number of the pulse from left to right, and the evolution of the pulse in the network along with the number of the cycle turns L follows the coupling mode equation idA_m/dL–κ_m(A_m-1+A_m+1) Where i is an imaginary unit, d is a derivative symbol, and κ_mSin (C) is the coupling strength between adjacent pulses, determined by the coupler splitting ratio C.

Example two

A method for regulating pulse coupling and evolution of an optical fiber network is realized by constructing a cellular time domain photonic lattice. On the basis of the optical fiber network in the first embodiment, the length of the original 4 segments of single-mode optical fibers is adjusted so that the time for the pulse to pass through each optical fiber satisfies t₁+t₂＝t₃+t₄，t₁-t₃＝t₂-t₄＝δt，t₂–t₁＝t₄–t₃The dotted line in the figure indicates the difference in length between the two fibers. At the same time, another 2 x 2 coupler 9 is added after the optical coupler 7, and the transmission time t is added between the two couplers₁₁And t₁₂Short

optical fibers

11 and 12 of (1), wherein t₁₂–t₁₁＝2δt。

The evolution of the pulses in the embodiments of the present invention will be further described below with reference to fig. 1(b) and fig. 3-4, including:

(1) the left loop in the optical fiber network contains a pulse sequence with a limited time interval delta T or delta T, and the pulse is transmitted in the single-mode optical fiber 1 for a time T₁ Rear entrance coupler 7, then transit time t in optical fiber 11₁₁The light enters the coupler 9, finally returns to the optical fiber 1 through the optical fiber 2 and the coupler 8, and completes one cycle in a clockwise direction;

(2) the right loop also contains a finite number of pulse sequences with time intervals delta T or delta T, and the delay difference delta T exists between the pulse sequences in the left loop and the pulse sequences in the right loop. The pulse in the loop enters the optical fiber 12 through the optical fiber 4 and the coupler 7 and is transmitted for time t₁₂＝t₁₁+2 δ t into coupler 9, and then transmitted through fiber 3 for t3 time, and then back to fiber 4 through coupler 8, completing the cycle in the counterclockwise direction;

(3) t is satisfied due to the time required for the pulse to pass through the

fibers

1 and 4₁–t₄δ t, as shown in fig. 3, left side loop inner t₀Time pulse and right side t₀Pulses at time-2 δ t are coupled in meet in coupler 7; and due to t₁₂＝t₁₁+2 δ t, left and right loop inner t₀The time pulse will enter the optocoupler 9 at the same time;

(4) after the pulses in the left and right loops pass through the

optical fibers

2 and 3, the pulses are generated due to t₂–t₃δ T + Δ T, left loop T₀Time pulse and right side t₀Pulses at time + deltat will simultaneously enter coupler 8 for interaction.

Specifically, as the number of cycles of pulses in the fiber optic network increases, a pulse train as shown in fig. 5 will be formed in the fiber loop, i.e., comprising a series of pulse wave packets having a time difference Δ T, each of which comprises a series of pulses spaced at intervals δ T. Mapping pulses into two-dimensional m-n plane by using coupling relation in network, i.e. dividing pulses by using time delta T, and placing each wave packet in left and right loops as a row in a crossed way along vertical direction, e.g. placing left loop T₀The time pulse is taken as the m-th pulse of the n-th row, and t in the right loop interacting with the m-th pulse₀-δt、t₀+ δ t and t₀Pulse at + Δ TThe impact coordinates are (m-1, n-1), (m +1, n-1) and (m, n +1), and by analogy, the honeycomb time domain photonic lattice shown in FIG. 4 can be constructed. At this time, the evolution of the pulse in the network can be analyzed and controlled by the lattice structure.

Specifically, in the present embodiment, the evolution of the pulse in the optical fiber network is mapped into the honeycomb lattice structure under the two-dimensional m-n space, and the evolution of the pulse in the network can be formed by idA/dL- (kappa)₁B_r1+κ₂B_r2+κ₃B_r3) Where A, B is used to characterize the lattice point, κ, corresponding to the time of the pulse₁、κ₂And kappa₃The coupling coefficient, which represents the energy of the pulses between the grid points, is determined by the splitting ratio of the

couplers

7, 9 and 8, and the subscripts r1, r2 and r3 represent the vector direction of the coupling between the grid points.

EXAMPLE III

A method for regulating pulse coupling and evolution of optical fiber network is realized by constructing a rectangular photon lattice with a heart time domain. On the basis of the optical fiber network in the first embodiment, the lengths of the single-mode optical fibers 1 to 4 are adjusted so that the transmission time of the pulse in the optical fiber satisfies the condition t₁+t₂＝t₃+t₄，t₁-t₃＝t₂-t₄＝2δt，t₂–t₁＝t₄–t₃The dotted line in the figure indicates the difference in length between the two fibers. While the

optical couplers

7 and 8 are followed by the 2 x 2 couplers 9 and 10 and between the couplers are added short

optical fibres

11, 12 and 13, 14 with a length difference of 2 deltat.

The evolution of the pulses in the embodiments of the present invention will be further described below in conjunction with fig. 1(c) and fig. 5-6, including:

(1) the left loop in the optical fiber network contains a finite number of pulse sequences with time intervals delta T or delta T, and the pulse sequences are transmitted in the optical fiber 1 for time T₁ Rear input coupler 7 for transmitting t in optical fiber 11₁₁After the time, the signal enters the coupler 9; the pulse enters the short optical fiber 13 through the optical fiber 2 and the coupler 8 for a transmission time t₁₃＝t₁₂Then the pulse returns to the single mode fiber 1 through the coupler 10, namely the pulse completes circulation along the counterclockwise direction;

(2) the loop on the right side of the fiber optic network contains a finite sequence of pulses spaced at intervals δ T or Δ T, and has a delay difference δ T from the pulses of the loop on the right side. Time t of transmission of pulse through single-mode fiber 4₄Into coupler 7 and then within optical fiber 12 for a time t₁₂＝t₁₁+2 δ t into coupler 9 and then pulsed for time t₃Enters the coupler 8 from the optical fiber 3 and transmits the time t in the optical fiber 14₁₄＝t₁₂Then enters the coupler 10 and finally returns to the optical fiber 4, namely the pulse completes the circulation along the counterclockwise direction;

(3) t is satisfied due to the transmission time of the pulse in the

optical fibers

1 and 4₁–t ₄2 δ t, giving rise to t in the left loop₀Time pulse and right side t₀The δ t pulses are coupled in coupler 7; and due to t₁₂＝t₁₁+2 δ t, left loop t₀Time pulse and right loop t₀The + δ t pulses also enter the coupler 9 simultaneously to interact;

(4) similar to the coupling process in (3), the pulses in the left and right loops after passing through the

optical fibers

2 and 3 due to t₂–t ₃2 δ T + Δ T, will result in T in the left loop₀The time pulse is coupled to the right loop t in the

couplers

8 and 10, respectively₀- δ T + Δ T and T₀The + δ T + Δ T pulses are coupled.

Specifically, as the number of cycles increases, a series of pulse wave packets at intervals Δ T are formed in the optical fiber network, and pulses in the network are divided in the same manner as in the embodiment, for example, T in the loop on the left side of the system₀The time pulse is placed at the (m, n) position in the m-n plane coordinate system, and t in the right loop is coupled with the time pulse₀T and t₀The pulses at the +/-delta T + delta T time are positioned at the (m +/-1, n-1) and (m +/-1, n +1) coordinate positions in the m-n plane, and by analogy, the pulse distribution in the optical fiber network can be mapped to a rectangular centromere photonic lattice structure, and the pulse evolution is regulated and controlled by means of lattice analysis, wherein the lattice structure is shown in figure 6.

Specifically, the pulse time domain waveform changes along with the increase of the number of the cycle turns L, and the evolution process is flexibleOver evolution equation idA_m,n/dL–κ₁A_m-1,n-1–κ₂A_m+1,n-1–κ₃A_m-1,n+1–κ₄A_m+1,n+1Is described as 0, where i is an imaginary symbol, dA_m,nthe/dL represents the pulse amplitude A at (m, n) coordinates in a two-dimensional plane_m,nDifferential of number of evolution turns, κ₁、κ₂、κ₃And kappa₄Depending on the splitting ratio of the

couplers

7, 9, 8 and 10.

Example four

A method for regulating pulse coupling and evolution of optical fiber network is realized by constructing rectangular time domain photonic crystal lattice. Keeping the transmission time satisfying the condition t on the basis of the optical fiber network in the first embodiment₁＝t₃，t₂＝t₄，t₂–t₁＝t₄–t₃And simultaneously adding a phase modulator and a dispersion fiber with equal length in the left loop and the right loop respectively to modulate the frequency spectrum and the time domain waveform of the pulse respectively, wherein the period of the phase modulation signal is TM.

The evolution of the pulses in the embodiments of the present invention is further described below in conjunction with fig. 1(d) and fig. 7-8, including:

(1) the left loop in the optical fiber network contains a limited interval of T_MOr Δ T, which, during transmission in the single-mode fiber 1, passes through the dispersive fiber 13 and the phase modulator 15 in succession, and at the transmission time T₁Then, the pulse passes through the coupler 7, the single-mode fiber 2 and the coupler 8 in sequence, and finally returns to the fiber 1 to complete a cycle, wherein the time required for the pulse to pass through the fiber 2 is t₂；

(2) Similarly, the right loop of the network contains a gap T_MOr Δ T, the time T taken for the pulse to propagate in the single-mode optical fibre 4₄And passes through the dispersive fiber 14 and the phase modulator 16 at the same time, and then returns to the fiber 1 in a counterclockwise direction through the coupler 7, the single-mode fiber 2 and the coupler 8 to complete the circulation;

(3) as in the first embodiment, T in the network on the left side is under the action of the delay difference Δ T in the network₀Time pulse and right side t₀And t₀Pulses at + delta T respectively enter the

couplers

7 and 8 to interact;

(4) the stressed period of the phase modulators on the left side and the right side of the network is T_MIn combination with the dispersion provided by the fiber, when the pulse follows the nonlinear Schrodinger equation in the evolution process

Wherein the content of the first and second substances,

and

representing the partial derivative of the pulse amplitude a in the direction of the transmission distance z and time t, i being an imaginary unit. V is the amplitude, beta, of the phase-modulated signal₂For group velocity dispersion coefficient, the pulses are discrete in the time dimension under both effects and are represented by T_MEnergy coupling occurs for the intervals.

Further, as the number of cycles increases, under the combined action of phase modulation, fiber dispersion and delay variation in the network, a pulse train as shown in fig. 7 is formed, i.e., a series of pulse wave packets with a Δ T interval are formed, and the interval between adjacent pulses in the wave packets is T again_M. The optical pulse is mapped to a two-dimensional plane, a rectangular photon time domain lattice as shown in fig. 8 can be equivalently constructed in a time dimension, namely, under an m-n coordinate system, the coupling of the pulse along the m direction is realized through phase modulation and dispersion; the delay difference then causes the pulses to interact in the n direction. Under the combination of the two, the evolution of the number L of the cycle turns of the pulse in the system follows a coupling mode equation idA_m,n/dL–[κ_m(A_m-1,n+A_m+1,n)+κ_n(A_m,n-1+A_m，n+1)]0, where A is the time domain pulse amplitude, k_mAnd kappa_nThe coupling strength of the pulse in the lattice along the m direction and the n direction is respectively regulated and controlled by the phase modulation depth and the coupler splitting ratio.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A fiber optic network, comprising: a first optical fiber (1), a second optical fiber (2), a third optical fiber (3), a fourth optical fiber (4), a first optical coupler (7) and a second optical coupler (8);

the input end of the first optical coupler (7) is connected with one end of the first optical fiber (1), the coupling end is connected with one end of the fourth optical fiber (4), the straight-through end is connected with one end of the second optical fiber (2), and the isolation end is connected with one end of the third optical fiber (3);

the input end of the second optical coupler (8) is connected with the other end of the second optical fiber (2), the coupling end is connected with the other end of the third optical fiber (3), the straight-through end is connected with the other end of the first optical fiber (1), and the isolation end is connected with the other end of the fourth optical fiber (4);

the length difference between the first optical fiber (1) and the third optical fiber (3) is 0, and the length difference between the second optical fiber (2) and the fourth optical fiber (4) is 0; the length difference between the first optical fiber (1) and the second optical fiber (2) and the length difference between the fourth optical fiber (4) and the third optical fiber (3) satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 2 times the width of the incident pulse.

2. The fiber optic network of claim 1, wherein the evolution of pulses with cycle number L in the network follows the following coupled mode equation:

idA_m/dL-K_m(A_m-1+A_m+1)＝0

wherein i is an imaginary unit, d is a derivative symbol, A_mFor the complex amplitude of the m-th pulse, the subscript m denotes the number of pulses in the pulse sequence on the time axis, A₀The time difference between the pulses is determined by the length difference between the first optical fiber (1) and the second optical fiber (2) and the length difference between the fourth optical fiber (4) and the third optical fiber (3) for the complex amplitude of the incident pulse, K_mSin C is the coupling strength between adjacent pulses and is determined by the optical coupler splitting ratio C.

3. A fiber optic network, comprising: a first optical fiber (1), a second optical fiber (2), a third optical fiber (3), a fourth optical fiber (4), a first optical coupler (7), a second optical coupler (8), a third optical coupler (9), a fifth optical fiber (11), and a sixth optical fiber (12);

the input end of the first optical coupler (7) is connected with one end of the first optical fiber (1), the coupling end is connected with one end of the fourth optical fiber (4), the straight-through end is connected with one end of the fifth optical fiber (11), and the isolation end is connected with one end of the sixth optical fiber (12);

the input end of a third optical coupler (9) is connected with the other end of a fifth optical fiber (11), the coupling end is connected with the other end of a sixth optical fiber (12), the straight-through end is connected with one end of a second optical fiber (2), and the isolation end is connected with one end of a third optical fiber (3);

the length difference between the first optical fiber (1) and the third optical fiber (3) is 0, the length difference between the second optical fiber (2) and the fourth optical fiber (4) is 0, the length difference between the fifth optical fiber (11) and the sixth optical fiber (12) is positive, and the two pulse wave packets are not overlapped; the length difference between the first optical fiber (1) and the second optical fiber (2) and the length difference between the fourth optical fiber (4) and the third optical fiber (3) satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times the width of the incident pulse.

4. The fiber optic network of claim 3, wherein the evolution of pulses with cycle number L in the network follows the following coupled mode equation:

idA/dL-(K₁B_r1+K₂B_r2+K₃B_r3)＝0

wherein i is an imaginary unit, d is a derivative symbol, A, B is used for representing a lattice point corresponding to the moment of the pulse, and K₁、K₂And K₃The coupling coefficient representing the pulse energy between the lattice points is composed of a first optical coupler and a second optical couplerThe split ratios of the coupler and the third optical coupler are determined, and subscripts r1, r2 and r3 indicate the vector directions of coupling between the lattice points.

5. A fiber optic network, comprising: a first optical fiber (1), a second optical fiber (2), a third optical fiber (3), a fourth optical fiber (4), a first optical coupler (7), a second optical coupler (8), a third optical coupler (9), a fourth optical coupler (10), a fifth optical fiber (11), a sixth optical fiber (12), a seventh optical fiber (13), and an eighth optical fiber (14);

the input end of the second optical coupler (8) is connected with the other end of the second optical fiber (2), the coupling end is connected with the other end of the third optical fiber (3), the straight-through end is connected with one end of the seventh optical fiber (13), and the isolation end is connected with one end of the eighth optical fiber (14);

the input end of the fourth optical coupler (10) is connected with the other end of the seventh optical fiber (13), the coupling end is connected with the other end of the eighth optical fiber (14), the straight-through end is connected with the other end of the first optical fiber (1), and the isolation end is connected with the other end of the fourth optical fiber (4);

the length difference between the first optical fiber (1) and the third optical fiber (3) is 0, and the length difference between the second optical fiber (2) and the fourth optical fiber (4) is 0; the length difference between the first optical fiber (1) and the second optical fiber (2) and the length difference between the fourth optical fiber (4) and the third optical fiber (3) need to satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times the width of the incident pulse;

the length difference between the fifth optical fiber (11) and the sixth optical fiber (12) and the length difference between the seventh optical fiber (13) and the eighth optical fiber (14) satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that two adjacent pulse wave packets are not overlapped.

6. The fiber optic network of claim 5, wherein the evolution of pulses with cycle number L in the network follows the following coupled mode equation:

idA_m，n/dL-K₁A_m-1，n-1-K₂A_m+1，n-1-K₃A_m-1，n+1-K₄A_m+1，n+1＝0

wherein i is an imaginary symbol, idA_m，nthe/dL represents the pulse amplitude A at (m, n) coordinates in a two-dimensional plane_m，nDifferential of number of evolution turns, K₁、K₂、K₃And K₄The coupling coefficient representing the inter-lattice pulse energy depends on the splitting ratios of the first, second, third and fourth optical couplers.

7. A fiber optic network, comprising: a first optical fiber (1), a second optical fiber (2), a third optical fiber (3), a fourth optical fiber (4), a first optical coupler (7), a second optical coupler (8), a first phase modulator (17), and a second phase modulator (18);

the input end of the second optical coupler (7) is connected with one end of the first optical fiber (1), the coupling end is connected with one end of the fourth optical fiber (4), the straight-through end is connected with one end of the second optical fiber (2), and the isolation end is connected with one end of the third optical fiber (3);

a first phase modulator (17) is connected in the first optical fiber (1), and a second phase modulator (18) is connected in the fourth optical fiber (4);

the length difference between the first optical fiber (1) and the third optical fiber (3) is 0, and the length difference between the second optical fiber (2) and the fourth optical fiber (4) is 0; the length difference between the first optical fiber (1) and the second optical fiber (2) and the length difference between the fourth optical fiber (4) and the third optical fiber (3) satisfy the following conditions: 1) the two length differences are equal and positive numbers; 2) the length difference ensures that the time delay difference is more than or equal to 10 times of the phase modulation period.

8. The fiber optic network of claim 7, wherein the evolution of pulses with cycle number L in the network follows the following coupled mode equation:

idA_m，n/dL-[K_m(A_m-1，n+A_m+1，n)+K_n(A_m，n-1+A_m，n+1)]＝0

wherein, idA_m，nthe/dL represents the pulse amplitude A at (m, n) coordinates in a two-dimensional plane_m，nDifferential of number of evolution turns, K_mAnd K_nThe coupling strength of the pulse in the lattice along the m direction and the n direction is respectively regulated and controlled by the modulation amplitude of the phase modulator and the splitting ratio of the second optical coupler and the third optical coupler.

9. The fiber optic network of any of claims 1-8, wherein the first through fourth optical fibers are single mode fibers, wherein there is indirectly a dispersion compensating fiber.