阅读说明：本技术 一种基于多重光学双稳态的全光数字编码器 (All-optical digital encoder based on multiple optical bistable states ) 是由 李永逵 于 2021-09-22 设计创作，主要内容包括：本发明提供了一种基于多重光学双稳态的全光数字编码器,属于全光通讯技术领域。本全光数字编码器包括若干第一电介质层A、若干第二电介质层B和两个石墨烯单层G,全光数字编码器表示为：ABABB-(1)GB-(2)BABABBBBBBBBBABABB-(2)GB-(1)BABA,其中B-(1)GB-(2)和B-(2)GB-(1)表示石墨烯单层嵌入第二电介质层内形成的三明治结构；第一电介质层和第二电介质层为两种折射率不同的均匀电介质薄片,全光数字编码器存在两个双峰共振的光学分形态,光学分形态对应的电场具有局域作用,两个石墨烯单层分别嵌于双峰共振分形态的局域电场最强位置,使石墨烯单层的三阶非线性效应得到增强,进而实现低阈值多重光学双稳态；多重双稳态的上、下阈值对应着数字编码器的各态的编码触发阈值。本发明具有触发阈值低等优点。(The invention provides an all-optical digital encoder based on multiple optical bistable states, and belongs to the technical field of all-optical communication. The all-optical digital encoder comprises a plurality of first dielectric layers A, a plurality of second dielectric layers B and two graphene single layers G, and is represented as follows: ABABB 1 GB 2 BABABBBBBBBBBABABB 2 GB 1 BABA, in which B 1 GB 2 And B 2 GB 1 Representing a sandwich structure formed by embedding the graphene monolayer into the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes, the all-optical digital encoder has two optical fractal modes of bimodal resonance, an electric field corresponding to the optical fractal modes has a local effect, and the two graphene single layers are respectively embedded in the strongest positions of the local electric fields of the bimodal resonance fractal modes, so that the three-order nonlinear effect of the graphene single layers is enhanced, and further the low-threshold multiple optical bistable state is realized; the multiple bistable upper and lower thresholds correspond to the encoding trigger thresholds of the respective states of the digital encoder.The invention has the advantages of low triggering threshold value and the like.)

1. The all-optical digital encoder based on multiple optical bistable states is characterized by comprising a plurality of first dielectric layers A, a plurality of second dielectric layers B and two graphene single layers G, wherein the multilayer structure of the all-optical digital encoder is represented as follows: ABABB₁GB₂BABABBBBBBBBBABABB₂GB₁BABA, in which B₁GB₂And B₂GB₁Representing a sandwich structure formed by embedding the graphene monolayer into the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes, the all-optical digital encoder has two optical fractal modes of double-peak resonance, an electric field corresponding to the optical fractal modes has a local effect, and the two graphene single layers are respectively embedded in the strongest positions of the local electric fields of the two optical fractal modes, so that the three-order nonlinear effect of the graphene single layers is enhanced, and further the low-threshold multiple optical bistable state is realized; the upper and lower thresholds of the multiple bistable states correspond to the coding trigger thresholds of each state of the digital coder; the first dielectric layer and the second dielectric layer each have a thickness of 1/4 at the respective optical wavelength.

2. The multi-optic bistable-based all-optical digital encoder of claim 1, wherein the matrix material of said first dielectric layer is lead telluride, and the matrix material of said second dielectric layer is cryolite.

3. The all-optical digital encoder based on multiple optical bistability as claimed in claim 1 or 2, wherein the upper threshold, the lower threshold and the threshold interval of the multiple bistability are regulated by incident wavelength.

4. The plenoptic digital encoder based on multiple optical bistability according to claim 1 or 2, wherein the upper threshold, the lower threshold and the threshold interval of the multiple bistability are regulated by the chemical potential of the graphene monolayer.

Technical Field

The invention belongs to the technical field of all-optical communication, and relates to an all-optical digital encoder based on multiple optical bistable states.

Background

In all-optical communication, signals need to be stored, encoded, relayed, timed, amplified, shaped, etc. in the optical domain, which requires an all-optical digital encoder, and an optical bistable digital encoder is an optically controlled optical all-optical digital encoder.

Optical bistability is a nonlinear optical effect based on the optical kerr effect of a material. When the incident light is sufficiently strong, one input intensity may correspond to two different output intensities, i.e. one incident intensity may induce two stable resonant output states. When the optical bistable is applied to an all-optical digital encoder, the output light intensity in the bistable jumps at the upper and lower thresholds of the input light intensity, and the jump state is encoded. The greater the bistable threshold, the greater the light intensity required to trigger the encoder to encode. On the other hand, when the power of the device is increased, the stability thereof is deteriorated and the requirement for the heat radiation condition is also increased. In addition, as the interval between the upper and lower thresholds is smaller, the discrimination of each coding state is weaker, and the coding error rate becomes larger. Therefore, research on digital encoders based on optical bistability is currently focused on how to lower the threshold of optical bistability and increase the interval between upper and lower thresholds by new materials and new structures.

To achieve low threshold optical bistability, materials with large third-order nonlinear coefficients are sought on the one hand; on the other hand, the optical Kerr effect is directly proportional to the local electric field, so that the local electric field can be enhanced by optimizing the system structure, and the third-order nonlinear effect of the material can be improved.

Graphene is an ultrathin two-dimensional material, has excellent conductivity, and the surface conductivity of the graphene can be flexibly regulated and controlled through the chemical potential of the graphene. Importantly, graphene has a considerable third-order optical nonlinear coefficient. This makes graphene a hot-gate material for achieving low-threshold optical bistability. In addition, in order to further reduce the bistable threshold value, the local electric field of the graphene can be enhanced by utilizing the surface plasmon polariton of the graphene, so that the nonlinear effect of the graphene is improved; graphene can also be embedded into a defect layer of a photonic crystal, and the non-linear effect of graphene is enhanced by utilizing the electric field locality of defect pairs.

In the wave vector space, a photonic crystal has a photonic band structure similar to an electron band in a semiconductor. Light waves within the band gap will be totally reflected without transmission. If defects are introduced into the photonic crystal, a defective mode, i.e., a transmission mode, appears in the transmission spectrum. The transmission mode has strong local property to the electric field and is often used to enhance the third-order nonlinear effect of the material. In quasi-photonic crystals or aperiodic photonic crystals, natural defect layers exist, and the number of defect modes increases in a geometric progression along with the increase of sequence numbers, so that the quasi-photonic crystals or the aperiodic photonic crystals are ideal structures for enhancing local electric fields.

Low-threshold optical bistability can be achieved by embedding graphene into a Thue-Morse (T-M) photonic crystal. The T-M sequence is mathematically a quasi-periodic sequence, and the corresponding T-M photonic crystal is quasi-periodic. The T-M photonic crystal is provided with a plurality of defect cavities, and an optical fractal resonance state exists. In a composite structure of graphene and T-M photonic crystal, the optical bistable state with low threshold can be realized by utilizing the locality of optical fractal to an electric field, and the threshold of the optical bistable state is about GW/cm²(gigawatts per square centimeter).

In order to further reduce the threshold value of optical bistability, graphene is compounded with Octonacci photonic crystal, and the threshold value of the optical bistability can be as low as 100MW/cm²(MW/cm²Representing megawatts per square centimeter). . Octonacci photon is also a quasi-periodic photonic crystal, has the characteristic of optical fractal, and the optical fractal has stronger locality to an electric field, so that the nonlinear effect of graphene can be greatly enhanced. However, the resonant transmission modes of an Octonacci photonic crystal are independent of each other, and a certain interval exists between adjacent resonant modes, which can be used to realize a plurality of low-threshold optical bistability independent of each other. Whether a composite structure of other quasi-periodic photonic crystals and graphene can be obtained or not is a key research direction in the field, so that on one hand, the threshold value of optical bistable state is further reduced, on the other hand, an optical fractal state of bimodal or multimodal resonance is obtained, multiple bistable state or multiple stable state is realized, and further, the polymorphic all-optical encoder of low trigger threshold value is realized.

Disclosure of Invention

The present invention is directed to provide an all-optical digital encoder based on multiple optical bistable states, and the technical problem to be solved by the present invention is how to obtain a low-trigger-threshold multi-state all-optical digital encoder.

The purpose of the invention can be realized by the following technical scheme: a kind ofThe all-optical digital encoder based on multiple optical bistable states is characterized by comprising a plurality of first dielectric layers A, a plurality of second dielectric layers B and two graphene single layers G, wherein the multilayer structure of the all-optical digital encoder is represented as follows: ABABB₁GB₂BABABBBBBBBBBABABB₂GB₁BABA, in which B₁GB₂And B₂GB₁Representing a sandwich structure formed by embedding the graphene monolayer into the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indexes, the all-optical digital encoder has two optical fractal modes of double-peak resonance, an electric field corresponding to the optical fractal modes has a local effect, and the two graphene single layers are respectively embedded in the strongest positions of the local electric fields of the two optical fractal modes, so that the three-order nonlinear effect of the graphene single layers is enhanced, and further the low-threshold multiple optical bistable state is realized; the first dielectric layer and the second dielectric layer each have a thickness of 1/4 at the respective optical wavelength.

The composite structure comprises two graphene single layers and a Kantol (Cantor) photonic crystal with a sequence number N ═ 3, wherein the Kantol photonic crystal is ABBBABBBBBBBBBBBABABABABA, and letters A, B respectively represent two uniform dielectric sheets with different refractive indexes; the Comptor photonic crystal has two optical component forms with double-peak resonance, an electric field corresponding to the component forms has locality, 2 graphene single layers are embedded into the strongest position of the local electric field of one of the double-peak resonance component forms, and the composite structure can be expressed as follows on the whole: ABABB₁GB₂BABABBBBBBBBBABABB₂GB₁BABA, wherein G represents a graphene monolayer; the local electric field of the position of the graphene single layer is strongest, so that the three-order nonlinear effect of the graphene is greatly enhanced, the low-threshold multiple optical bistable state is further realized, and the threshold value of the optical bistable state in the structure can be as low as 100kW/cm²This is 3 orders of magnitude lower than the threshold for optical bistability in the composite structure of Octonacci photonic crystals and graphene.

In a composite structure based on Cantor photonic crystals and graphene, the nonlinear effect of graphene is considered, and when the incident wavelength is located near a bimodal resonance fractal state, multiple low-threshold optical bistable states exist. The multiple optical bistable state can be used for a multi-state digital encoder, the triggering threshold value of each state of the encoder and the threshold interval are increased along with the increase of the chemical potential and the incident wavelength of the graphene, and therefore, the triggering threshold value of the encoder can be flexibly regulated and controlled through the chemical potential and the incident wavelength of the graphene.

Furthermore, the matrix material of the first dielectric layer is lead telluride, and the matrix material of the second dielectric layer is cryolite.

Furthermore, the upper threshold, the lower threshold and the threshold interval of the multiple bistable states are regulated and controlled through incident wavelengths.

Furthermore, the upper threshold, the lower threshold and the threshold interval of the multiple bistable states are regulated and controlled through the chemical potential of the graphene monolayer.

Drawings

Fig. 1 is a schematic diagram of a composite structure of a Cantor photonic crystal with a sequence number N ═ 3 and graphene.

Fig. 2 is a linear transmission spectrum of light in a Cantor photonic crystal with the number N ═ 3.

Fig. 3(a) is a graph showing a normalized electric field distribution of a bimodal resonant optical fractal corresponding to a wavelength λ of 2.0577 μm; fig. 3(b) shows a normalized electric field distribution of a bimodal resonant optical fractal having a wavelength λ of 2.0406 μm.

In fig. 4, (a) is the input-output light intensity relationship corresponding to the chemical potential μ ═ 0.4 eV; fig. 4(b) is a graph showing the influence of the chemical potential of graphene on the input-output intensity relationship.

FIG. 5 is a graph (a) showing the input-output intensity relationship for different incident wavelengths; fig. 5(b) is a graph of the variation of the upper and lower thresholds of the III-th bistable state with the incident wavelength.

Fig. 6 is a schematic diagram of a triplex optical bistable based multivalued all-optical digital encoder.

In the figure, a first dielectric layer; B. a second dielectric layer; G. a graphene monolayer.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

Mathematically, the iterative rule for the kantor (Cantor) sequence is: s₀＝A，S₁＝ABA，S₂＝ABA(BBB)ABA,S₃＝S₂(BBB)²S₂，……，S_N＝S_N-1(BBB)^N-1S_N-1… … where N (0, 1, 2, 3, … …) is the sequence number, S_NThe Nth term representing the sequence; (BBB)^N-1Is represented by 3^N-1And B. The letters A, B in the corresponding Cantor photonic crystal respectively represent two homogeneous dielectric flakes having different refractive indices. The composite structure of the Cantor photonic crystal with the sequence number N-3 and graphene is shown in FIG. 1. The dielectric sheets and the single-layer graphene are sequentially arranged along the Z axis, and the central position of the structure is a 0 point.

Symbol I₁For incident light, symbol I₂Is the outgoing light. This structure may also be denoted ABABB₁GB₂BABABBBBBBBBBABABB₂GB₁BABA, wherein the letter G denotes single layer graphene; the matrix material of A is lead telluride with refractive index n_a＝4.1；B、B₁And B₂The matrix materials of (A) are all cryolite with refractive index n_b1.35. The incident light is transverse magnetic wave and is vertically incident from the left. Dielectric sheets A and B are both 1/4 optical wavelengths thick, i.e. A has a thickness d_a＝λ₀/4/n_a0.0945 μm (μm denotes μm), where λ₀1.55 μm as the center wavelength, and B has a thickness d_b＝λ₀/4/n_b＝0.287μm，B₁Has a thickness of d_b1＝0.1443μm，B₂Has a thickness of d_b20.1427 μm, satisfies the condition d_b1+d_b2＝d_b,。

Single layer graphene has a thickness of about 0.33nm (nm means nanometers), which corresponds to the size of one atom. With respect to the dielectric sheet A, B, B₁And B₂The thickness of graphene is negligible. Here, the ambient temperature is set to 300K (K denotes kelvin), and the relaxation time τ of the electrons in the graphene is 0.5ps (ps denotes picosecond).

When the influence of graphene is not considered, the incident light frequency is changed, and fig. 2 shows a linear transmission spectrum of light in the Cantor photonic crystal with the sequence number N-3. The ordinate T represents the transmittance of light waves; abscissa (ω - ω)₀)/ω_gapDenotes a normalized angular frequency, where ω is 2 π c/λ, ω₀＝2πc/λ₀And ω_gap＝4ω₀arcsin│(n_a-n_b)/(n_a+n_b)|²And/pi respectively represents incident light angular frequency, incident light central angular frequency and angular frequency band gap, c is light speed in vacuum, and arcsin is an inverse sine function. At a normalized frequency of [ -1,1 [)]Within the interval, 8 transmission formants exist, the transmittance peak value is all 1, and the 8 transmission formants correspond to 8 resonance optical fractal. These 8 optical fractal states all have a local effect on the electric field. A bimodal resonance fractal (marked by an asterisk) exists on the left side of the spectral line, the corresponding wavelengths of the bimodal resonance fractal are 2.0577 μm and 2.0406 μm respectively, and the electric field distribution corresponding to the two wavelengths is given in the next step; the graphene is embedded at the position with the strongest local electric field, so that the nonlinear effect of the graphene is enhanced, and the low-threshold optical bistable state is realized; in addition, to achieve a low threshold multiple optical bistability, the incident wavelength must be properly red detuned relative to the 1 st bimodal resonant mode wavelength λ of 2.0577 μm.

The dielectric and the graphene are sequentially arranged from left to right along the horizontal direction according to a rule. Fig. 3(a) shows the electric field distribution corresponding to 2.0577 μm at the 1 st resonance wavelength λ in the bimodal resonant optical fractal to the left of the spectral line. The dotted lines represent the interfaces between two adjacent layers of dielectric, and 2 graphene monolayers G are respectively embedded at the positions of the structure where the electric field intensity is strongest. The ordinate represents the normalized electric field strength of the Z component. The distribution of the electric field energy in the structure is not uniform, and the locality exists; two maximum peaks exist in the electric field intensity, but the second maximum peak is slightly lower than the first maximum peak; the graphene single layer is just positioned at the strongest point of a local electric field, and the optical third-order nonlinear effect of the graphene is in direct proportion to the intensity of the local electric field, so that the nonlinear effect of the graphite is greatly enhanced. Fig. 3(b) shows the electric field distribution corresponding to the 2 nd resonance wavelength λ of 2.0406 μm in the left-hand bimodal resonance optical mode. The position with the strongest electric field intensity is superposed with the position with the strongest electric field intensity corresponding to the 1 st resonance wavelength; however, the first maximum peak is slightly lower than the second maximum peak.

The chemical potential is set to 0.4eV, the other parameters are kept constant, and fig. 4(a) shows the variation of output light intensity with input light intensity. The wavelength of the incident light is 2.085 μm, and there is a certain red detuning with respect to the first resonance wavelength of the bimodal resonance, 2.0577 μm. Abscissa I_iRepresenting input light intensity, ordinate I_oRepresenting the output light intensity; unit MW/cm²Representing megawatts per square centimeter. When the intensity increases to a certain value, 3S-shaped curve segments appear in the relation curve of the input-output intensity, which are respectively marked by the dotted oval boxes I, II and III and correspond to the triple optical bistable relation. In a composite system of Oconacci photonic crystal and graphene, the optical bistable threshold value is 100MW/cm²Magnitude; in the compounding of T-M photonic crystal and graphene, the optical bistable state is GW/cm²Magnitude; and in the composite structure of the Cantor photonic crystal of N-3 and graphene, the threshold value of optical bistable state is MW/cm²Magnitude. It can be seen that the bistable threshold can be greatly reduced by the compounding of the Cantor photonic crystal and graphene, compared with the Octonacci and T-M photonic crystals.

When the input light intensity is gradually increased from a relatively small value, the output light intensity jumps upwards at the right corner of the S curve segment of the section I, and the corresponding input light intensity is called as a first upper threshold value of the optical bistable state; when the input light intensity is gradually reduced from a relatively large value, a downward jump occurs in the output light intensity at the left corner of the S curve segment of the earth I segment, and the corresponding input light intensity at the moment is called as a first lower threshold value of the optical bistable state. The difference between the upper and lower thresholds is called the threshold interval.

When the input intensity is between the upper and lower threshold values, one input intensity corresponds to two output intensity values, which is called an optical bi-stable effect. In the profile of the input-output intensity relationship described above, there are three sigmoid curve segments, which are typical characteristics of triplet optical bistability, and this effect can be used in a multi-state all-optical digital encoder.

Of course, different incident wavelengths, or different chemical potentials of graphene, will correspond to different bistable curves and thresholds.

The fixed incident wavelength λ is 2.085 μm, and other parameters are kept constant, and fig. 4(b) shows the input-output light intensity relationship corresponding to different graphene chemical potentials μ. It can be seen that: input-output light intensity has a triply bistable relationship when μ ═ 0.4eV, 0.45eV, and 0.5 eV; increasing the mu value, wherein bistable curves corresponding to different chemical potentials are different, and the widths of upper and lower thresholds and the thresholds of the bistable states are different; as the chemical potential of the graphene increases, the bistable upper threshold value and bistable lower threshold value increase, and the bistable width between threshold values also increases, so that the upper threshold value and the lower threshold value and the threshold interval of multiple bistable states can be regulated and controlled through the chemical potential of the graphene.

When the chemical potential μ of the fixed graphene is 0.45eV, other parameters are kept unchanged, and fig. 5(a) shows the input-output light intensity relationship corresponding to different incident wavelengths. It can be seen that: given the 3 wavelength values λ 2.084 μm, 2.085 μm and 2.086 μm, the input-output all have a triply bistable relationship; the bistable curves corresponding to different incident wavelengths are different, namely the widths of the upper threshold value, the lower threshold value and the threshold value of the bistable state are different; as the incident wavelength increases, i.e., the amount of detuning increases, the bistable upper and lower thresholds increase, and the bistable threshold interval increases, as shown in fig. 5 (b). The ordinate thresh represents the threshold value of the bistable state. The upper and lower thresholds of the optical bistable state corresponding to the third sigmoid curve segment (marked by a dashed oval) in fig. 5(a) are selected as a function of wavelength. Upper Threshold and Lower Threshold represent bistable Upper and Lower thresholds, respectively. It can be seen that the triple bistability appears in the whole given wavelength interval of 2.083 μm ≦ λ ≦ 2.086 μm; the upper and lower thresholds and threshold intervals of the bistable state increase with increasing wavelength. Since the larger the amount of wavelength detuning, the more the difference needs to be made up by the nonlinear effect, the stronger the incident light energy needed to satisfy the resonance. Thus, the upper and lower thresholds and threshold intervals of the multiple bistable states can be tuned by the incident wavelength.

In a word, an optical fractal state of bimodal resonance exists in a composite structure of Cantor photonic crystal and graphene with a sequence number N-3, the optical fractal state has a strong local effect on an electric field, and 2 graphene single layers are just positioned at the strongest positions of the local electric field of the bimodal resonance fractal state respectively, so that the nonlinear effect of the graphene is greatly enhanced, and the low-threshold multiple optical bistable state is realized; threshold of optical bistability down to MW/cm²The magnitude is 6 magnitudes smaller than the threshold of the optical bistable state in the compounding of the T-M photonic crystal and the graphene, and is 2 magnitudes smaller than the threshold of the optical bistable state in the compounding of the Octonacci photonic crystal and the graphene. And the upper and lower thresholds and the threshold interval of the multiple optical bistable states can be flexibly regulated and controlled by the chemical potential and the incident wavelength of the graphene. The effect can be applied to a multi-state all-optical digital encoder.

The wavelength of incident light is set to be 2.085 μm, the chemical potential is 0.4eV, and a triple optical bistable phenomenon appears in the relation of input-output light intensity, and the principle of the triple optical bistable phenomenon is applied to a multi-state all-optical digital encoder as shown in fig. 6. When the input light intensity is gradually increased from a lower value, the output light intensity generates an upward jump at the right turning point of the I-th S-curve segment (positioned at the leftmost lower part of the curve), and the input light intensity I is adjusted_i＝I_u1Called the first bistable upper threshold, which corresponds to the coding 000 of the encoder, so I_i＝I_u1A trigger threshold called symbol 000 of the encoder; continuously increasing the input light intensity to the right corner of the S curve segment (located in the middle of the curve) of the II segment, corresponding to the second bistable upper threshold value I_i＝I_u2The output light level will have an upward jump corresponding to the encoder code 010, so I_i＝I_u2A trigger threshold of symbol 010 called encoder; then the input light intensity is continuously increased to the right corner of the S curve segment (positioned at the rightmost upper part of the curve) of the III segment, which corresponds to a third bistable upper threshold value I_i＝I_u3The output light intensity will then have an upward jump, which corresponds to the coding 100 of the encoder, and I_i＝I_u3Called the trigger threshold of the symbol 100 of the encoder.

When the input light intensity is gradually reduced from a larger value, the output light intensity generates a downward jump at the left turning point of the S curve segment of the III section to change the input light intensity I_i＝I_d3Called the third bistable lower threshold, which corresponds to the coding 101 of the encoder, and therefore also I_i＝I_d3A trigger threshold for symbol 101, called encoder; continuously reducing the input light intensity to the left corner of the S curve segment of the II segment corresponding to the second bistable lower threshold value I_i＝I_d2The output light level will have a downward jump corresponding to the encoder code 011, so I will also be_i＝I_d2A trigger threshold of symbol 011, called encoder; then, the input light intensity is continuously reduced to the left turning point of the section I S curve section, which corresponds to the first bistable lower threshold value I_i＝I_d1The output light intensity will then have a downward jump, which corresponds to the encoder encoding 001, so I will also be the same_i＝I_d3Called the trigger threshold for symbol 001 of the encoder.

Fig. 4(b) shows that the threshold of triplet optical bistability is influenced by the chemical potential of graphene. As the chemical potential of the graphene increases, the upper and lower thresholds, and the threshold interval of the corresponding S-curve segment increase. The upper and lower thresholds of the multiple bistable states correspond to the encoding trigger thresholds of the multi-state encoder, so that the encoding trigger thresholds corresponding to the states of the digital encoder can be flexibly regulated and controlled through the chemical potential of the graphene. This trigger threshold can also be tuned by the incident wavelength, as shown in fig. 5(a) and 5 (b). By changing the incident wavelength, the wavelength detuning amount is increased, the bistable upper threshold value, the bistable lower threshold value and the width between the threshold values are increased, so that the encoding trigger threshold values of various states of the digital encoder can be regulated and controlled.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.