JP4208366B2 - Optical coupler and optical multiplexer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention generally relates to an optical element, and more particularly to an optical element constituting an optical waveguide and used as an optical coupler or an optical power splitter.
In an optical information processing system that processes or transmits a large amount of information, an optical waveguide is one of the basic components. In such an optical information processing system, an optical coupler that combines a plurality of optical signals into an optical waveguide and combines them into a single optical signal, or an optical power splitter that decomposes a single optical signal into a plurality of optical signals is provided. It is often done. Particularly in recent large-capacity optical information processing systems, since each optical signal constitutes a so-called wavelength multiplexed (WDM) optical signal including optical signal components of a plurality of wavelengths, such an optical coupler or optical power splitter is also included. Therefore, it is necessary to handle such optical signal components having a plurality of wavelengths. In other words, the optical coupler or the optical power splitter that handles the wavelength multiplexed optical signal needs to have uniformly low optical loss with respect to the optical signal components of a plurality of wavelengths constituting the wavelength multiplexed optical signal.
[0002]
As a technique for handling such wavelength multiplexed optical signals, there is a so-called AWG (arrayed waveguide grating) configuration. However, such an AWG configuration is generally large and expensive, and thus an inexpensive optical coupler or optical power splitter. May have to be used.
[0003]
[Prior art]
FIG. 1 shows a configuration of an optical power splitter 10 designed for a single wavelength optical signal, which has been conventionally used. For example, see JP-A-8-201648.
Referring to FIG. 1, an optical power splitter 10 includes an optically transparent main body or slab 10A, and an incident side end face 10 of the slab 10A.₁The incident-side single-mode optical waveguide 10B formed on the slab 10A and the exit-side end face 10 of the slab 10A₂A plurality of output-side single mode optical waveguides 10C formed in₁-10C_FourThe incident light having the wavelength λ having the light intensity distribution 10b in the lateral direction, which is incident from the incident-side single-mode optical waveguide 10B, diffuses in the slab 10A and is reflected by the side wall surface, and then the emission Side end face 10₂The exit-side single-mode optical waveguide 10C₁-10C_FourIs incident on. That is, the slab 10A of FIG. 1 constitutes a multimode optical waveguide. At this time, the length of the slab 10A is set so that the emission side end face 10₂On the output side single mode optical waveguide 10C₁-10C_FourIs set so that the light intensity distribution 10c is maximized.
[0004]
For example, the physical length of the slab 10A in FIG._mmi, Physical width W_m, W optical width_eThe length L_mmiIs
L_mmi= 3L_c/ 4N (1)
And the output-side single mode optical waveguide 10C.₁-10C_FourMutual distance D_iIs
D_i= W_e/ N (2)
Determined by Where N is the exit-side single mode optical waveguide 10C.₁-10C_FourParameter L in equation (1)_cIs
L_c= (4/3) × n_r× (W_e ²/ Λ) (3)
Given in. Where n_rIs the effective refractive index in the lateral direction of the optical medium constituting the slab 10A. W_eIs W_mA little bigger than.
[0005]
Therefore, the length L_mmiFrom the previous equations (1) and (3),
L_mmi= 3L_c/ 4N = (1 / N) × n_r× (W_e ²/ Λ) (4)
Given in.
Length L of the slab 10A_mmiIs set according to the equation (4), the emission side end face 10 of the slab 10A.₂Above, the output-side single mode optical waveguide 10C₁-10C_FourA strong light intensity is obtained by a self-imaging effect generated as a result of interference of various modes in the slab 10A at a position corresponding to the optical waveguide 10C.₁-10C_FourAnd efficient slab coupling between the slab 10A.
[0006]
The power splitter 10 in FIG. 1 also functions as an optical coupler when the incident side and the emission side are interchanged.
[0007]
[Problems to be solved by the invention]
However, when the wavelength-multiplexed optical signal is supplied to the incident-side single-mode optical waveguide 10B in the optical power splitter 10 of FIG. 1, it can be understood from the fact that the equation (4) includes the wavelength λ as a parameter. Furthermore, although the optical loss is small for the optical signal component of a specific wavelength, the optical loss is very large for the optical signal components of other wavelengths. That is, at these wavelengths, the optimum L_mmiWill not match the length of the slab 10A.
[0008]
As described above, although the optical power splitter or the optical coupler 10 of FIG. 1 has a simple configuration and can be manufactured at a low cost, it has a problem that it is inappropriate for processing a wavelength multiplexed optical signal. .
Accordingly, it is a general object of the present invention to provide a new and useful optical waveguide that solves the above problems.
[0009]
A more specific object of the present invention is to provide an optical waveguide that has a simple configuration, can be formed at low cost, and functions as an optical coupler or an optical power splitter for wavelength multiplexed optical signals.
[0010]
[Means for Solving the Problems]
The present invention solves the above problem as described in claim 1.
An optical member made of an optically transparent medium, defined by a first end surface and a second end surface facing the first end surface;
A plurality of single-mode optical waveguides provided opposite the first end face and optically coupled to the optical member;
Another single-mode optical waveguide provided opposite the second end face and optically coupled to the optical member;
The first end surface of the optical member is provided corresponding to the plurality of single mode optical waveguides, and extends from the first end surface of the optical member toward the corresponding single mode optical waveguide. A plurality of extending portions connected to the single mode optical waveguide,
Each of the plurality of extending portions has a width wider than the corresponding single mode optical waveguide and a length corresponding to the wavelength of the optical signal transmitted through the single mode optical waveguide,
The optical waveguide according to claim 1, wherein the lengths are different from each other in the plurality of extending portions.
[0011]
The present invention also provides the above-mentioned problem, as described in claim 2, wherein the length is λ._nIs a wavelength of an optical signal transmitted through the corresponding single mode optical waveguide, and λc is an optical wavelength longer than the longest wavelength among λn (λc ≧ λ_n ^maxAs
L_{ext, n}≒ L_{mmi, c}× [(λ_c/ Λ_n-1],
L_{mmi, c}Is the light wavelength λ_cWith
L_{mmi, c}= (1 / N) × n_r× (W_e ²/ Λ_c),
Where n_rIs the effective refractive index of the optical member, N is the number of single-mode optical waveguides provided facing the first end face, and W_eThis is solved by the optical waveguide according to claim 1, which represents an effective optical width of the transparent optical member.
[0012]
The present invention also solves the above problem as described in claim 3.
In the first end surface, the plurality of extending portions are formed such that the longest one is located at the center and the shortest one is located at both side edges of the first end surface. This is solved by the optical waveguide according to claim 1 or 2.
The present invention also solves the above problems.
It solves with the optical waveguide as described in any one of Claims 1-3 which do not have the notch which exposes the said 1st end surface between these extension parts.
[0013]
The present invention also solves the above problems.
The optical waveguide according to any one of claims 1 to 3, wherein a space between the plurality of extending portions is defined by a slope oblique to the first end face. To do.
The present invention also solves the above problem as described in claim 4.
An optical waveguide according to any one of claims 1 to 3, a laser array optically coupled to the plurality of single mode optical waveguides, and optically coupled to the other single mode optical waveguide. This is solved by a multi-wavelength light source characterized in that it comprises a coupled optical amplifier.
[0014]
The present invention also solves the above problem as described in claim 5.
A first optical member made of an optically transparent medium, defined by an incident side end surface and an output side end surface facing the incident side end surface;
A plurality of incident-side single mode optical waveguides provided on the incident-side end face of the first optical member, each of which is physically connected to the incident-side end face of the first optical member;
Provided on the exit end face of the first optical member, each having a first end and a second end, the first end being physically connected to the exit end face of the optical member A plurality of separate single mode optical waveguides each having a different optical path length;
Optically transparent defined by an incident side end face to which the second end of each of the other single-mode optical waveguides is physically connected and an output side end face facing the incident side end face A second optical member made of a medium,
A plurality of exit-side single mode optical waveguides having an end optically coupled to the exit-side end face of the second optical member;
Provided corresponding to the plurality of exit-side single-mode optical waveguides, extending from the exit-side end surface of the second optical member toward the corresponding exit-side single-mode optical waveguide, A plurality of extensions physically connected to the single mode optical waveguide,
Each of the plurality of extending portions has a width wider than the corresponding output-side single mode optical waveguide and a length corresponding to the wavelength of an optical signal transmitted through the output-side single mode optical waveguide,
The length is solved by a multimode interference optical multiplexer characterized in that the plurality of extending portions are different from each other.
[Action]
According to the present invention, an optical member that is supplied with a wavelength-multiplexed optical signal via a single-mode optical waveguide, and multi-mode interference of the multiplexed optical signal in the optical member, Multiple optical signal components that make up a multiple optical signal and that output multiple optical signal components with different wavelengths to their corresponding single-mode optical waveguides, or multiple single-mode optical waveguides. A plurality of optical signals in the optical member, and a single wavelength multiplexed optical signal having the plurality of optical signals as components obtained as a result. In the optical coupler that outputs to the single-mode optical waveguide, the optical member is provided with a plurality of extending portions each having a length corresponding to the wavelength of the plurality of optical signals. Is varied for each wavelength of the optical signal components such length, also in the resulting optical power splitter, in the optical coupler, it is possible to minimize optical loss at each wavelength.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[referenceExample]
  2 (A) and 2 (B) show the present invention.Reference exampleThe structure of the optical waveguide 20 by is shown. 2A is a plan view of the optical waveguide 20, and FIG. 2B is a cross-sectional view.
  Referring to the cross-sectional view of FIG. 2B, the waveguide 20 has a core layer 22 made of InGaAsP having a thickness of about 300 nm formed on an InP substrate 21 also serving as a cladding layer by the MOVPE method or the MBE method, The core layer 22 and the clad layer 23 are patterned by the RIE method to form a mesa structure in a plan view shown in FIG. 2A. The clad layer 23 is made of InP having a thickness of about 300 nm.
[0016]
Next, referring to FIG. 2A, the optical waveguide 20 is used as an optical power splitter.₁And the output side end face 20 facing this.₂The physical width defined by_mThe multi-mode optical interference region 20A, and the incident side end face 20₁Has a wavelength of λ₁~ Λ_FourAn incident-side single-mode optical waveguide 20B that transmits the wavelength multiplexed optical signal is connected. Where λ₁> Λ₂> Λ_Three> Λ_FourAnd On the other hand, the emission side end face 20₂Each has a wavelength of λ₁~ Λ_FourMultiple output-side single-mode optical waveguides 20C for transmitting a plurality of optical signals₁~ 20C_FourAre optically coupled, but the optical waveguide 20C₂~ 20C_FourAbout the exit-side end face 20 of the multimode optical interference region 20A.₂Between each extension 20E₂~ 20E_FourIs interposed. The optical waveguide 20C is similar to the optical power splitter 10 of FIG.₁~ 20C_FourIs the emission side end face 20₂Above, uniform spacing W_e/ N substantially parallel to each other.
[0017]
Here, the length L of the multimode optical interference region 20A_mmiIs the single mode optical waveguide 20C.₁The wavelength emitted at₁(5) corresponding to the previous equation (4) based on the optical signal component of
L_{mmi, 1}= (1 / N) × n_r× (W_e ²/ Λ₁(5)
It is determined. However, in the example of FIG. 2, N = 4.
[0018]
In contrast, the extension 20E₂~ 20E_FourLength L_{ext, n}(Where n = 2-4)
L_{ext, n}≒ L_{mmi, 1}× [(λ₁/ Λ_n-1] (6)
Set according to.
As a result, the incident side optical waveguide 20B has a wavelength of λ.₁~ Λ_FourEven when a wavelength-multiplexed optical signal including the optical signal components is supplied, each of the output-side single-mode optical waveguides 20C₁~ 20C_FourThe optical loss at is minimized and efficient optical coupling is achieved.
[0019]
FIG. 3 shows the transmissivity for each wavelength in the optical power splitter 20 having the configuration shown in FIGS. Shown in comparison with the conventional one shown.
Referring to FIG. 3, the dotted line is the conventional case, and it can be seen that significant attenuation, that is, optical loss occurs on both sides of the center wavelength of 1550 nm, whereas the optical power splitter according to the present invention indicated by the solid line in the figure. 20 shows that the light loss is minimized at any wavelength.
[0020]
  2A and 2B, the configuration of FIG. 1 is the same, but the incident side end face 20 is the same.₁ A slight taper angle θ is formed. This is because the portion where the light intensity becomes substantially zero at the time of optical interference in the multimode optical interference region 20A is the end face 20.₁ As a result, it is formed as a result of cutting off such a portion.
[No.1Example]
  The optical power splitter 20 also functions as an optical coupler when the directions of incident light and outgoing light are reversed.
[0021]
  FIG. 4 shows the first aspect of the present invention.1The structure of the optical coupler 30 by an Example is shown. However, the same reference numerals are given to the parts described above in FIG.
  Referring to FIG. 4, the optical coupler 30 has substantially the same configuration as that of the optical power splitter 20, but in the optical coupler 30 of the present embodiment, the single mode optical waveguide 20C.₁ ~ 20C₄ Through each wavelength λ₁ ~ Λ₄ Are incident on the multimode optical interference region 20A, and multimode interference occurs in the multimode optical interference region 20A. As a result, a strong light intensity is obtained by the self-imaging effect, and the end face 20₁ Of the single mode optical waveguide 20B, and the wavelength of the single mode optical waveguide 20B is λ.₁ ~ Λ₄ A wavelength-multiplexed optical signal on which the optical signal is superimposed is obtained.
[0022]
The situation is the same in the optical power splitter 20 of the previous embodiment, but in the optical coupler 30 according to the present embodiment, the extension portion 20E is used.₂~ 20E_FourHowever, it should be noted that a multimode optical waveguide similar to the multimode optical interference region 20A is formed. For this reason, the extension 20E₂~ 20E_FourCorresponds to the corresponding single mode optical waveguide 20C.₂~ 20C_FourThe single mode optical waveguide 20C.₂~ 20C_FourThe optical signal guided through the extension portion 20E₂~ 20E_FourIs diffused as indicated by a broken line in FIG. 4 and enters the multimode light interference region 20A. For this reason, the extension 20E₂~ 20E_FourSingle-mode optical waveguide 20C that does not interfere with the diffusion of such optical signals.₁~ 20C_FourMust be set to a width greater than the width of Otherwise, the preferred features of the present invention of FIG. 3 cannot be realized. The result of FIG. 3 shows that the extended portion 20E.₂~ 20E_FourThis is a case in which the diffusion of the optical signal in is not hindered at all.
[0023]
  As described above, the single-mode optical waveguide 20C₁ ~ 20C₄ Is set to be sufficiently large so that the guided optical signal is sufficiently diffused to enter the multimode optical interference region 20A, not only the optical coupler 30 of FIG. This is also important in the optical power splitters A) and (B).
[No.2Example]
  As described above, the single-mode optical waveguide 20C₁ ~ 20C₄ It is very important in the optical waveguide of the present invention that the width of the optical waveguide is set to be sufficiently large so that the guided optical signal is sufficiently diffused and incident on the multimode optical interference region 20A. However, satisfying this requirement, as can be easily seen from FIG. 4, is particularly the longest extension 20E.₄ Is difficult. In the example of FIG. 4, the extension portion 20E.₄ In the optical waveguide 20C₄ It can be seen that the diffusion of the optical signal incident from is actually hindered.
[0024]
  On the other hand, FIG.2The structure of the optical coupler 40 by an Example is shown. However, in FIG. 5, the same reference numerals are assigned to portions corresponding to the portions described above, and description thereof is omitted.
  Referring to FIG. 5, in the optical coupler 40, each incident-side single mode optical waveguide 20C used in the previous embodiment is used.₂ ~ 20C₄ Extension part 20E corresponding to₂ ~ 20E₄ Instead of the incident side end face 20.₂ A single stepped multimode waveguide region 20E is formed thereon. The step-like multimode waveguide region 20E has the respective incident-side single mode optical waveguides 20C.₁ ~ 20C₄ The height of the staircase, that is, the incident side end face 20₂ The distance measured from is determined according to the equation (6).
[0025]
In such a configuration, the optical waveguide 20C in the configuration of FIG._FourIs transmitted through the extension portion 20E._FourThe wavelength incident on the multimode optical interference region 20A while diffusing is_FourPart of the incident light (reference numeral 20 in FIG._c4The problem that the incident light is also subjected to undesirable multimode interference other than normal multimode interference in the multimode light interference region 20A is a problem with the separate extension portions 20E.₂~ 20E_FourThis is mitigated by using a single stepped extension 20E instead of.
[0026]
  The optical coupler 40 in FIG. 5 can also be used as an optical power splitter by reversing the directions of incident light and outgoing light.
[No.3Example]
  FIG. 6 shows the first aspect of the present invention.3The structure of the optical coupler 50 by an Example is shown. However, in FIG. 6, the same reference numerals are assigned to portions corresponding to the portions described above, and the description thereof is omitted.
[0027]
Referring to FIG. 6, in the present embodiment, the incident-side single mode optical waveguide 20C.₁~ 20C_FourAnd the highest step portion of the step-like multimode waveguide region 20E, that is, the optical waveguide 20C._FourThe step corresponding to is the optical waveguide 20C.₂And the optical waveguide 20C corresponding to the step_ThreeIt is comprised so that it may be located in the middle with the step part corresponding to. As a result, the optical waveguide 20C_FourThe optical signal guided therethrough is also diffused unimpeded in the stepped multimode waveguide region 20E, and the optical coupler 50 exhibits the ideal light transmission characteristics described above with reference to FIG. In this embodiment, the optical waveguide 20C₁~ 20C_FourThe wavelength exiting₁~ Λ_FourThe incident light is only subjected to normal multimode interference action occurring in the multimode light interference region 20A.
[0028]
  Similar to the previous embodiment, when the directions of incident light and outgoing light are reversed in the optical coupler 50 of FIG. 6, the optical coupler 50 acts as a high-efficiency optical power splitter.
  Other features of the present embodiment are clear from the description of the previous embodiment, and a description thereof will be omitted.
[No.4Example]
  FIG. 7 shows the first aspect of the present invention.4The structure of the optical coupler 60 by an Example is shown. However, in FIG. 7, the same reference numerals are given to the parts described above, and the description thereof is omitted.
[0029]
Referring to FIG. 7, an optical coupler 60 is a modification of the optical coupler 40 of FIG. 5, and the incident side end face 20 is formed between the steps constituting the stepped multimode waveguide region 20 </ b> E.₂End face 20 oblique to_ThreeIt has the structure tied in. Such a configuration is easier to form than the optical coupler 40 of FIG. 5, and as a result, the single mode optical waveguide 20C.₁~ 20C_FourEven if the number is increased further, the manufacturing problem of the optical coupler 60 does not occur.
[0030]
  Other features and advantages of this embodiment are the same as those described above, and a description thereof will be omitted.
[No.5Example]
  FIG. 8 shows the first aspect of the present invention.5The structure of the optical coupler 70 by an Example is shown. However, in FIG. 8, the same reference numerals are given to the parts described above, and the description thereof is omitted.
[0031]
Referring to FIG. 8, the optical coupler 70 has the characteristics of the optical coupler 50 described above with reference to FIG. 6 and the characteristics of the optical coupler 60 described with reference to FIG. The highest step portion is arranged at the center portion, and the lowest step portion is arranged at both side portions, and the step portions are connected by a linear end face.
Such a configuration can be easily manufactured even when the number of waveguides included in the incident-side single-mode optical waveguide 20C increases, and an optical signal transmitted to the multimode optical interference region 20A via any of the waveguides. Even so, the stepped multimode waveguide region 20E does not receive any extraneous interference and receives only the interference from the multimode optical interference region 20A. As a result, the optical signals having the respective wavelengths transmitted to the multimode optical interference region 20A through the incident side optical waveguide 20C are transmitted to the output side single mode optical waveguide 20B formed at the output end of the region 20A. Injected with high efficiency, as a result, a wavelength-multiplexed optical signal is obtained in the output-side single mode optical waveguide 20B. Such an optical coupler can minimize optical loss even when the wavelength of the incident optical signal is variously different.
[0032]
  In the example of FIG. 8, the single-mode optical waveguide constituting the incident-side single-mode optical waveguide 20C is coupled to a laser diode array having a corresponding wavelength, and the output-side single-mode optical waveguide 20B is coupled to an optical amplifier. Has been.
  Similar to the previous embodiment, the optical coupler 70 of FIG. 8 can also be used as an optical power splitter.
[No.6Example]
  In the above embodiments, the number of single-mode optical waveguides on the output side is one in the case of an optical coupler and the number of single-mode optical waveguides on the incident side in the case of an optical power splitter. However, the present invention is not limited to such a specific configuration, and an optical coupler provided with a plurality of single mode optical waveguides on the output side, or light provided with a plurality of single mode optical waveguides on the incident side. A power splitter can also be configured.
[0033]
FIG. 9 shows a configuration of an optical coupler 80 in which a plurality of single-mode optical waveguides are provided also on such an emission side. However, in FIG. 9, the part demonstrated previously is attached | subjected with the same referential mark, and description is abbreviate | omitted.
Referring to FIG. 9, the incident side end face 20₂Each has a wavelength of λ₁, Λ₂, Λ_ThreeSingle-mode optical waveguide 20C for transmitting a single optical input signal₁~ 20C_ThreeAnd the optical waveguide 20C₂And the multimode optical interference region 20A between the extended portions 20E constituting the multimode optical waveguide₂However, the optical waveguide 20C_ThreeSimilarly, between the multimode optical interference region 20A and the extended portion 20E constituting the multimode optical waveguide._ThreeHas been inserted. Meanwhile, the optical waveguide 20C₁Are directly connected to the multimode optical interference region 20A. The extending portion 20E₂20E_ThreeIs determined by the equation (6).
[0034]
In the configuration in which the number of output side optical waveguides is 2 and the number of incident side waveguides is N, the length L of the multimode optical interference region 20A_mmiIs L in the previous equation (3)_cUse
L_mmi= L_c/ N
On the other hand, the output side optical waveguide 20B₁20B₂Is an effective optical width W of the multimode optical interference region 20A._eUse W_eIs set equal to / 3. In this case, the input side optical waveguide 20C₁~ 20C_ThreeIs the effective optical width W_e2W using_e/ 3N is set.
[0035]
9 can be easily expanded when the number of incident side optical waveguides is N and the number of output side optical waveguides is N. In this case, the length L of the multimode optical interference region 20A_mmiFor L in the formula (3)_cUse
L_mmi= 3L_c/ N
Is set by Further, the interval between the incident side and the outgoing side optical waveguides may be set arbitrarily.
[0036]
  Similar to the previous embodiment, the optical coupler of FIG. 9 can also be used as an optical power splitter by reversing the directions of incident light and outgoing light.
[No.7Example]
  FIG. 10 shows the first aspect of the present invention.7The structure of the multimode interference optical multiplexer 90 by an Example is shown.
[0037]
  Referring to FIG. 10, the optical multiplexer 90 has a wavelength of λ.₁ ~ Λ₄ An incident-side single-mode optical waveguide 91 for transmitting the optically multiplexed signal of the above, an optical multiplexing interference element 92 having a conventional configuration in which the incident-side single-mode optical waveguide 91 is physically connected, and the light having the conventional configuration A single mode optical waveguide 93 is connected to the multiple interference element 92.₁ ~ 93₄ An optical multiple interference element having the configuration described in the previous embodiment, optically coupled via an optical internal connection circuit 93 comprising92,94 And an exit side single mode optical waveguide 95 optically coupled to the optical multiple interference element 94, and each of the plurality of single mode optical waveguides constituting the exit side single mode optical waveguide 95 is It is connected to an extending portion corresponding to the extending portion 20 </ b> E provided on the output side end face of the optical multiple interference element 94. As a result, the optical multiplexed signal λ in the incident-side single mode optical waveguide 91 is obtained.₁ ~ Λ₄ Is demultiplexed and separated into optical signal components λ₁ .About..lamda.4 are output to the respective optical waveguides constituting the emission-side single mode optical waveguide 95. FIG.
[0038]
Further, in the optical multiplexer 90, an optical signal λ having a wavelength corresponding to each of the optical waveguides constituting the single mode optical waveguide 95.₁~ Λ_FourIs supplied to the single-mode optical waveguide 91.₁~ Λ_FourAs a constituent component, a multiplexed optical signal obtained by wavelength multiplexing is obtained.
Also in the present embodiment, as in the previous embodiment, the length of each part constituting the extending portion 20E is changed in accordance with the wavelength of the optical signal to be transmitted.
[0039]
Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope described in the claims.
[0040]
【The invention's effect】
  BookAccording to the invention, the optical member includes an optical member to which a wavelength-multiplexed optical signal is supplied through a single mode optical waveguide, and the multiplexed optical signal is multi-mode interference in the optical member, and the multiplexing is performed. Multiple optical signal components with different wavelengths that make up the optical signal are output to the corresponding single mode optical waveguides, or through multiple single mode optical waveguides. An optical member to which an optical signal is supplied, and multimode interference of the optical signal in the optical member, and the resulting wavelength-multiplexed optical signal including the plurality of optical signals as a single component Even in an optical coupler or an optical multiplexer that outputs to a single mode optical waveguide, by providing a plurality of extending portions each having a length corresponding to a wavelength of each of the plurality of optical signals, the optical member The effective length of the optical member is changed for each wavelength of the optical signal component, so that the optical loss at each wavelength is minimized in the optical power splitter, optical coupler, and optical multiplexer. It becomes possible to do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a conventional optical power splitter.
[Figure 2] (A), (B)Reference exampleIt is a figure which shows the structure of the optical power splitter by.
FIG. 3 is a diagram showing transmission characteristics of the optical power splitter of FIG. 2;
FIG. 4 shows the first aspect of the present invention.1It is a figure which shows the structure of the optical coupler by an Example.
FIG. 5 shows the first of the present invention.2It is a figure which shows the structure of the optical coupler by an Example.
FIG. 6 shows the first of the present invention.3It is a figure which shows the structure of the optical coupler by an Example.
FIG. 7 shows the first of the present invention.4It is a figure which shows the structure of the optical coupler by an Example.
FIG. 8 shows the first of the present invention.5It is a figure which shows the structure of the optical coupler by an Example.
FIG. 9 shows the first of the present invention.6It is a figure which shows the structure of the optical coupler by an Example.
FIG. 10 shows the first of the present invention.7It is a figure which shows the structure of the optical multiplexer by an Example.
[Explanation of symbols]
10,20 Optical power splitter
10₁, 10₂, 20₁, 20₂End face
10A Slab
10B, 10C₁-10C_Four20B₁20B₂20C₁~ 20C_Four  Single mode optical waveguide
10b, 10c Light intensity distribution
20A Multimode optical interference region
20E₁~ 20E_Four  Extension
20E Stepped multimode waveguide region
21 InP substrate
22 InGaAsP core layer
23 InP clad so
30, 40, 50, 60, 70, 80 Optical coupler
90 Optical multiplexer
91 Incident-side single-mode optical waveguide
92,94 Optical multiple interference element
93 Internal connection circuit
95 Emission-side single-mode optical waveguide

Claims (6)

A slab-like optical member made of an optically transparent medium, defined by a first end face and a second end face facing the first end face;
A plurality of single mode optical waveguides provided opposite the first end face and optically coupled to the optical member;
Another single mode optical waveguide provided opposite the second end face and optically coupled to the optical member;
The first end surface of the optical member is provided corresponding to the plurality of single mode optical waveguides, and extends from the first end surface of the optical member toward the corresponding single mode optical waveguide. A plurality of extending portions connected to the single mode optical waveguide,
Each of the plurality of extending portions has a width wider than the corresponding single mode optical waveguide and a length corresponding to the wavelength of the optical signal transmitted through the single mode optical waveguide,
The lengths are different from each other in the plurality of extending portions ,
The plurality of single mode optical waveguides are provided at mutual intervals equal to a value obtained by dividing the optical width of the slab-like optical member by the number of the plurality of single mode optical waveguides,
The optical member includes a substrate, a core layer formed on the substrate, and a cladding layer formed on the core layer,
The core layer, the optical coupler you characterized as having a higher refractive index none of the substrate and the cladding layer. The length is the wavelength of the optical signals transmitted through the single-mode optical waveguide for the corresponding lambda _n, the most long have optical wavelength of _{λ n (λ c = λ n} max) λc,
L _{ext, n ≈L mmi, c} × [(λ _c / λ _n ) -1],
L _{mmi, c} is L _{mmi, c} = (1 / N) × n _r × (W _e ² / λ _c ), using the light wavelength λ _c .
However n _r is the effective refractive index of the optical member, N is the number of said single mode optical waveguide which is provided to face the first end surface, the W _e represents an optical effective width of the transparent optical member The optical coupler according to claim 1, which is given by: 3. The optical coupler according to claim 1, wherein the substrate is an InP substrate, the core layer is an InGaAsP layer, and the cladding layer is an InP layer. In the first end surface, the plurality of extending portions are formed such that the longest one is located at the center and the shortest one is located at both side edges of the first end surface. The optical coupler according to any one of claims 1 to 3, wherein the optical coupler is provided . 5. The optical coupler according to claim 1 , a laser array optically coupled to the plurality of single-mode optical waveguides, and optically coupled to the another single-mode optical waveguide. A multi-wavelength light source comprising: A slab-shaped first optical member made of an optically transparent medium, defined by an incident-side end surface and an exit-side end surface facing the incident-side end surface;
A plurality of incident-side single mode optical waveguides provided on the incident-side end face of the first optical member, each of which is physically connected to the incident-side end face of the first optical member;
Provided on the exit end face of the first optical member, each having a first end and a second end, the first end being physically connected to the exit end face of the optical member A plurality of first exit side single-mode optical waveguides each having a different optical path length;
An optical element defined by an incident-side end face to which the second end of each of the first outgoing-side single-mode optical waveguides is physically connected, and an outgoing-side end face facing the incident-side end face; A slab-shaped second optical member made of a transparent medium,
A plurality of second exit-side single-mode optical waveguides having an end optically coupled to the exit-side end face of the second optical member;
A plurality of second output-side single mode optical waveguides extending from the output-side end face of the second optical member toward the corresponding second output-side single mode optical waveguide. A plurality of extending portions physically connected to the second output side single-mode optical waveguide,
Each of the plurality of extending portions has a width wider than the corresponding second emission-side single mode optical waveguide and a length corresponding to the wavelength of an optical signal transmitted through the emission-side single mode optical waveguide. Have
The lengths are different from each other in the plurality of extending portions ,
In the second optical member, the plurality of first emission-side single mode optical waveguides are formed on the incident-side end face thereof, and the width of the slab-shaped second optical member is set to be the plurality of first emission-side single waves. Provided with a mutual spacing equal to the value divided by the number of mode optical waveguides,
In the second optical member, the plurality of second output-side single mode optical waveguides are formed on the output-side end face thereof, and the width of the slab-shaped second optical member is set to the plurality of second output-side single units. Provided at a mutual interval equal to the value divided by the number of one-mode optical waveguides,
Each of the first and second optical members includes a substrate, a core layer formed on the substrate, and a cladding layer formed on the core layer,
The optical coupler according to claim 1, wherein the core layer has a higher refractive index than any of the substrate and the clad layer .

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