CN102736182B - Planar waveguide-type opto-isolator - Google Patents

Abstract

The invention discloses a planar waveguide-type opto-isolator, which comprises a core layer, wherein the core layer comprises a first waveguide, a first directional coupler, an upper interference arm, a lower interference arm, a second directional coupler, a 1*2 coupler and a second waveguide which are successively connected, wherein the upper interference arm and the lower interference arm are arranged in parallel; the first directional coupler is also connected with a third waveguide of a semi-circular ring; the third waveguide is connected with a fourth waveguide; the first waveguide is an upstream signal input waveguide; the second waveguide is an input waveguide of a downstream signal and an echo signal; and the third waveguide of the semi-circular ring and the fourth waveguide can be used for outputting the echo signal. According to the planar waveguide-type opto-isolator disclosed by the invention, the echo signal can not be reversely output from the original input port. In addition, the isolator has a small insertion loss for the upstream signal and the downstream signal.

Description

Planar waveguide-type optoisolator

Technical field

The present invention, about a kind of optoisolator, refers to a kind of for the optical fiber communication midplane waveguide type single-fiber bidirectional photoelectric device planar waveguide-type optoisolator of reflective isolation back and forth especially.

Background technology

In optical fiber telecommunications system, semiconductor laser is reflective very responsive to returning, and this time reflective meeting causes semiconductor laser unstable properties.Therefore, need optoisolator isolation this time reflective.

Existing optoisolator mostly is classical optoisolator in the market, as adopted Faraday magneto-optical rotating crystal type optoisolator, birefringece crystal type optoisolator, for the encapsulation of type coaxial photoelectric device.For planar waveguide-type (PLC, Planar Lightwave Circuit) photoelectric device, classical optoisolator is difficult for integration packaging in device, its main cause is that the size of isolator own is larger, and isolator is placed perpendicular to optical propagation direction, the package dimension that can increase device, the material of classical isolator is different from the material of planar waveguide-type photoelectric device in addition, has larger insertion loss.

Be referred from waveguide type Mach Zehnder interference instrument (MZI, Mach-Zahnder interferometer) dual wavelength is had to minute wave property preferably, adopt similar interferometer structure, then in conjunction with coupling mechanism, can realize the propagation of light wave specific direction.The structure of Mach Zehnder interference instrument comprises two identical 50: 50 directional coupler I, II and two interference arms, as shown in Figure 1, interferes arm can cause the phase differential of two-beam ripple, utilizes two-beam to interfere at coupling mechanism II place, for dual wavelength λ ₁, λ ₂, form λ ₁at output terminal 7, grow mutually, at output terminal 8, disappear mutually, λ ₂at output terminal 7, disappear mutually, long mutually at output terminal 8, thereby realize the function of partial wave.

Yet Mach Zehnder interference instrument is 2 * 2 type elements, can not realize the function of single fiber input single fiber output.By the output terminal 7,8 in interferometer rear end, increase by 1 * 2 coupling mechanism, can realize the function of upward signal single fiber output, but for downgoing signal, destroyed long, the condition that disappears mutually mutually of Mach Zehnder interference instrument, made Mach Zehnder interference instrument cannot realize single fiber output.Therefore need to improve interferometer.

As shown in Figure 2, first for downgoing signal, by waveguide 9, inputted, the two-beam ripple that is 50: 50 by 1 * 2 coupling mechanism partial wave afterwards, is designated as respectively E ₇, E ₈, two light waves are complex amplitude information, comprise amplitude and phase place.For simplifying technique, directional coupler I, II adopt identical symmetrical structure (its splitting ratio is no longer 50: 50), note wavelength X ₁, λ ₂propagation constant in directional coupler I, II is respectively k _{λ 1}, k _{λ 2}, the efficient coupling distance of coupling mechanism is l, note α _λ=k _λl, waveguide 9 incident light waves are E ₀, meet:

$\left[\begin{array}{c}{E}_1\\ E_2\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\α}& i\sin \mathrm{\α}\\ i\sin \mathrm{\α}& \cos \mathrm{\α}\end{array}\right]\left[\begin{array}{cc}\exp \left[\mathrm{i\β}(L+\mathrm{\ΔL})\right]& 0\\ 0& \exp \left(\mathrm{i\βL}\right)\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\α}& i\sin \mathrm{\α}\\ i\sin \mathrm{\α}& \cos \mathrm{\α}\end{array}\right]\left[\begin{array}{c}{E}_7\\ E_8\end{array}\right]---\left(1\right)$

Wherein β is for interfering the propagation constant of light wave in arm.

If meet the following conditions:

ΔL·β _λ1＝2mπ+2α _λ1、ΔL·β _λ2＝2nπ+2α _λ2，m、n＝0，±1，±2... (2)

Now for λ ₁, E _{2, λ 1}=E ₀, E _{1, λ 1}=0, for λ ₂, E _{1, λ 2}=E ₀, E _{2, λ 2}=0, i.e. signal λ ₁completely from port 2 outputs, signal λ ₂from port one, export completely.Illustrated that echoed signal can not enter upward signal λ ₁passage in, therefore can oppositely not export from former input port, play the effect of isolation, simultaneously to downgoing signal λ ₂zero-decrement passing through.

For upward signal, by waveguide 1 input at port one place, the light wave fields of incident is E ' ₀,

$\left[\begin{array}{c}{E}_7\\ E_8\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\α}& i\sin \mathrm{\α}\\ i\sin \mathrm{\α}& \cos \mathrm{\α}\end{array}\right]\left[\begin{array}{cc}\exp \left[\mathrm{i\β}(L+\mathrm{\ΔL})\right]& 0\\ 0& \exp \left(\mathrm{i\βL}\right)\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\α}& i\sin \mathrm{\α}\\ i\sin \mathrm{\α}& \cos \mathrm{\α}\end{array}\right]\left[\begin{array}{c}{E}_0^{\′}\\ 0\end{array}\right]---\left(3\right)$

If meet the following conditions

ΔL·β _λ1＝2mπ+2α _λ1、ΔL·β _λ2＝2nπ+2α _λ2，m、n＝0，±1，±2...

sin(2α _λ1)＝0 (4)

Now for λ ₁, the splitting ratio of directional coupler I, II is 0: 100, the feature of this directional coupler is that port one is inputted, port 4 outputs; Port 2 inputs, port 3 outputs, as shown in Figure 3.

E now _{7, λ 1}=E ' ₀, E _{8, λ 1}=0, signal is completely from output terminal 7 outputs.So upward signal λ ₁when 1 * 2 coupling mechanism closes ripple, can not interfere, light wave is undamped.

Optoisolator is for upward signal λ in a word ₁undamped passing through, plays buffer action for echo; To downgoing signal λ ₂zero-decrement passing through.

Optoisolator of the present invention is just based on above analysis and calculating.

Summary of the invention

In view of this, fundamental purpose of the present invention is to provide a kind of upward signal and downgoing signal is had very little insertion loss and echoed signal played to the planar waveguide-type optoisolator of buffer action.

For achieving the above object, the invention provides a kind of planar waveguide-type optoisolator, it includes sandwich layer, described sandwich layer includes connected successively first wave guide, the first directional coupler, parallel upper interference arm and the lower interference arm arranging, the second directional coupler, 1 * 2 coupling mechanism, the second waveguide, this first directional coupler is also connected with the 3rd waveguide of semicircular ring, the 3rd waveguide is connected with the 4th waveguide, this first wave guide is the input waveguide of upward signal, the second waveguide is the input waveguide of downgoing signal and echoed signal, this first directional coupler and the second directional coupler are in order to the transverse coupling of light beam, on this, interference arm and lower interference arm are in order to introduce coherent phase potential difference, this 1 * 2 coupling mechanism is in order to partial wave and close ripple, the 3rd waveguide of this semicircular ring and the 4th waveguide are in order to export echoed signal.

Described 1 * 2 coupling mechanism comprises parallel upper arm and the underarm arranging.

Described the first directional coupler and the second directional coupler are 0: 100 coupling mechanism.

Described upward signal enters isolator by first wave guide, and upward signal enters lower interference arm after by the first directional coupler, by entering the underarm of 1 * 2 coupling mechanism after the second directional coupler, finally by the second waveguide, is exported afterwards; Described downgoing signal is inputted by the second waveguide, after the energy distribution of 1 * 2 coupling mechanism, by upper arm and underarm, transmitted respectively, two paths of signals enters upper interference arm and lower interference arm after by the second directional coupler, and upper and lower interference arm exists phase differential, cause the change of two bundle signal phase information, by after the first directional coupler, two-way light interferes again, for downgoing signal, meets in the interference of first wave guide place long mutually, in the 3rd waveguide place, interfere and disappear mutually, downgoing signal is exported by first wave guide.

Described echoed signal is interfered and is disappeared mutually at first wave guide place, and long mutually in the 3rd waveguide place interference, echoed signal is exported by the 3rd waveguide, enters afterwards the 4th waveguide output.

Described the first directional coupler, the second directional coupler, 1 * 2 coupling mechanism and upper interference arm and lower interference arm all include curved waveguide, and the radius-of-curvature of this curved waveguide is all greater than 4mm.

The phase differential that planar waveguide-type optoisolator utilization of the present invention interferes arm to be introduced makes echo interfere and disappear mutually at former input port place, thereby cannot oppositely export from former input port; In addition, this isolator has very little insertion loss to upward signal and downgoing signal.

Accompanying drawing explanation

Fig. 1 is existing waveguide type Mach Zehnder interference instrument structural representation;

Fig. 2 is improved waveguide type Mach Zehnder interference instrument structural representation;

Fig. 3 is 0: 100 directional coupler beam propagation schematic diagram;

Fig. 4 is planar waveguide-type optoisolator plan view of the present invention;

Fig. 5 is the upward signal propagation figure of planar waveguide-type optoisolator of the present invention;

Fig. 6 is the downgoing signal propagation figure of planar waveguide-type optoisolator of the present invention;

Fig. 7 is the echoed signal propagation figure of planar waveguide-type optoisolator of the present invention;

Fig. 8 is the wherein a kind of structural representation that the present invention is based on silica-based planar waveguide-type optoisolator;

Fig. 9 is the cross section structure schematic diagram of optoisolator of the present invention.

Embodiment

For ease of structure of the present invention and the effect that reaches are had to further understanding, the existing preferred embodiment that develops simultaneously is by reference to the accompanying drawings described in detail as follows.

In the present invention the implementation of waveguiding structure and material can adopt following any: 1. structure adopts hole buried, material be take silicon as substrate, above substrate, prepare silicon dioxide under-clad layer, above under-clad layer, the silicon dioxide sandwich layer of germanium is mixed in preparation, prepares silicon dioxide top covering above sandwich layer; 2. structure adopts ridged mode, and material be take silicon as substrate, prepares germanium silicon core layer on substrate; 3. it is buried that structure adopts half hole, and material be take lithium niobate as substrate, and substrate top surface is prepared doped titanium lithium niobate sandwich layer; 4. structure adopts silicon mode on insulation course, and material be take silicon as substrate, prepares oxygen buried layer above substrate, prepares silicon core layer above oxygen buried layer.The 1st kind of mode of take is example, as shown in Fig. 8 and Fig. 9.

As shown in Fig. 8 and Fig. 9, the perspective view of planar waveguide-type optoisolator of the present invention, that optoisolator comprises from the bottom to top is successively silica-based 20, under-clad layer 21, sandwich layer 22 are parallel to each other with the plane of top covering 23, four.As shown in Figure 4, sandwich layer 22 of the present invention includes connected successively first wave guide 10,0: 100 the first directional coupler 12 (in Fig. 4, circle dotted line indicates), the parallel upper interference arm arranging 13 and lower interference arm 14,0: 100 the second directional coupler 15 (in Fig. 4, circle dotted line indicates), 1 * 2 coupling mechanism (it comprises the parallel upper arm arranging 16 and underarm 17), the second waveguide 11, the 3rd waveguide 18, the three waveguides 18 that the first directional coupler 12 is also connected with semicircular ring are connected with the 4th waveguide 19.

First wave guide 10 is upward signal λ ₁input waveguide, the second waveguide 11 is downgoing signal λ ₂and echoed signal λ ₁the input waveguide of (identical with the wavelength of upward signal), the effect of the first directional coupler 12 and the second directional coupler 15 is transverse couplings of light beam, meet formula (4), upper interference arm 13 is to introduce coherent phase potential difference with the effect of lower interference arm 14, meet formula (2), the effect of 1 * 2 coupling mechanism is partial wave and close ripple, and the 3rd waveguide 18 of semicircular ring and the effect of the 4th waveguide 19 are output echoed signal λ ₁.

As shown in Figure 5, the upward signal of planar waveguide-type single-fiber bidirectional device of the present invention (being that laser instrument transmits) wavelength is λ ₁, downgoing signal (being that detector receives signal) wavelength is λ ₂.Upward signal λ ₁by first wave guide 10, enter isolator, according to background knowledge, upward signal λ ₁by entering lower interference arm 14 after the first directional coupler 12, afterwards by entering the underarm 17 of 1 * 2 coupling mechanism after the second directional coupler 15, finally by the second waveguide 11 outputs.As shown in Figure 6, downgoing signal λ ₂by the second waveguide 11 inputs, after the energy distribution of 1 * 2 coupling mechanism, respectively by upper arm 16, underarm 17 transmission, two paths of signals enters upper and lower interference arm 13,14 after by the second directional coupler 15, because upper and lower interference arm 13,14 exists phase differential, cause the change of two bundle signal phase information, then by after the first directional coupler 12, two-way light interferes, for downgoing signal λ ₂meet and at first wave guide 10 places, interfere longly mutually, the 3rd waveguide 18 places interference disappears mutually, so downgoing signal λ ₂by first wave guide 10, exported.The implementation of upper and lower interference arm 13,14 phase differential has two kinds, first kind of way is by introducing the length difference Δ L of upper and lower interference arm 13,14, length difference Δ L and phase delta phi meet Δ φ=Δ L * 2 π/λ, the second way, by phase modulation component, is directly modulated upper interference arm 13 or lower interference arm 14.As shown in Figure 7, for the laser instrument echoed signal λ on optical fiber link ₁, meet at first wave guide 10 places and interfere and disappear mutually, long mutually in the 3rd waveguide 18 places interference, so echoed signal λ ₁by the 3rd waveguide 18 outputs, enter afterwards the 4th waveguide 19 outputs, therefore can not enter in first wave guide 10, thereby get rid of back the reflective impact on laser performance, play and isolate back reflective object.

The refractive index of sandwich layer is determined according to different needs, and its scheme of joining choosing mainly contains two kinds: 1. refractive index contrast Δ is 0.75%, and waveguide is rectangular waveguide, and cross section lateral dimension is 6um * 6um, for the demand of conventional waveguide chip; 2. refractive index contrast Δ is 1.5%, and waveguide is rectangular waveguide, and cross section lateral dimension is 4um * 4um, for compared with the demand of miniature chip.

Directional coupler, 1 * 2 coupling mechanism and interference arm all include curved waveguide, and the radius-of-curvature of this curved waveguide is all greater than 4mm, can effectively reduce the loss causing because of waveguide bend.Planar waveguide-type isolator adopts identical material and substrate with planar waveguide-type single-fiber bidirectional device, and the waveguide dimensions of substrate thickness, cladding thickness, sandwich layer is all identical, therefore more easily integrated and preparation.

Planar waveguide-type optoisolator of the present invention is for optical fiber communication planar waveguide-type single-fiber bidirectional photoelectric device, utilizes the phase differential of interfering arm to be introduced to make echo interfere and disappear mutually at former input port place, thereby cannot oppositely export from former input port; In addition, this isolator has very little insertion loss to upward signal and downgoing signal.The present invention adopts more ripe mixing integrated technology and plane wave waveguide technology, take silicon as substrate, silicon dioxide be covering, the silicon dioxide of mixing germanium is sandwich layer, its mature preparation process, structure is simpler, and size is little, adopts waveguide material and the substrate identical with planar waveguide-type single-fiber bidirectional device, easy of integration, be convenient to batch production.

The above, be only preferred embodiment of the present invention, is not intended to limit protection scope of the present invention.

Claims (2)

1. a planar waveguide-type optoisolator, it includes sandwich layer, it is characterized in that, described sandwich layer includes connected successively first wave guide, the first directional coupler, parallel upper interference arm and the lower interference arm arranging, the second directional coupler, 1 * 2 coupling mechanism, the second waveguide, this first directional coupler is also connected with the 3rd waveguide of semicircular ring, the 3rd waveguide is connected with the 4th waveguide, this first wave guide is the input waveguide of upward signal, the second waveguide is the input waveguide of downgoing signal and echoed signal, this first directional coupler and the second directional coupler are in order to the transverse coupling of light beam, on this, interference arm and lower interference arm are in order to introduce coherent phase potential difference, this 1 * 2 coupling mechanism is in order to partial wave and close ripple, the 3rd waveguide of this semicircular ring and the 4th waveguide are in order to export echoed signal, described the first directional coupler and the second directional coupler are 0:100 coupling mechanism, and described echoed signal is interfered and disappeared mutually at first wave guide place, and long mutually in the 3rd waveguide place interference, echoed signal is exported by the 3rd waveguide, enter afterwards the 4th waveguide output,

Described 1 * 2 coupling mechanism comprises parallel upper arm and the underarm arranging;

Described upward signal enters isolator by first wave guide, and upward signal enters lower interference arm after by the first directional coupler, by entering the underarm of 1 * 2 coupling mechanism after the second directional coupler, finally by the second waveguide, is exported afterwards; Described downgoing signal is inputted by the second waveguide, after the energy distribution of 1 * 2 coupling mechanism, by upper arm and underarm, transmitted respectively, two paths of signals enters upper interference arm and lower interference arm after by the second directional coupler, and upper and lower interference arm exists phase differential, cause the change of two bundle signal phase information, by after the first directional coupler, two-way light interferes again, for downgoing signal, meets in the interference of first wave guide place long mutually, in the 3rd waveguide place, interfere and disappear mutually, downgoing signal is exported by first wave guide.

2. planar waveguide-type optoisolator as claimed in claim 1, it is characterized in that, described the first directional coupler, the second directional coupler, 1 * 2 coupling mechanism and upper interference arm and lower interference arm all include curved waveguide, and the radius-of-curvature of this curved waveguide is all greater than 4mm.