CN1601949B - A Dielectric Film Dense Wavelength Division Multiplexer Filter - Google Patents

Abstract

A dielectric film type dense wavelength division multiplexing filter has a structure that: Sub/(HL)^N1H8L(HL) ⁸HL(HL)^N2H6L(HL)⁹HL(HL)⁹H4L(HL)⁹HL(HL)⁸H2L(HL) ⁸H0.404H1.21L/Air, wherein H is tantalum pentoxide Ta₂O₅L is silicon dioxide SiO₂The coefficient N1 of the dielectric film layer is 8-11, and the coefficient N2 is 9-11; the other structure of the invention is as follows: Sub/(HL)^N3H6L(HL)⁸HL(HL)⁹H6L(HL)^N4HL(HL)⁹H4L(HL)⁹HL(HL)⁸H2L(HL)⁸H0.404H1.21L/Air, wherein H is Ta₂O₅Tantalum pentoxide, L being silicon dioxide SiO₂The coefficient N3 of the dielectric film layer is 8-12, and the coefficient N4 is 9-11. The invention provides a filter with excellent performance for the wavelength division multiplexer with the channel spacing of 50GHz by reasonably designing the structure of the dielectric film type dense wavelength division multiplexer filter and correctly controlling the thickness of the film layer, and simultaneously reduces the communication cost.

Description

A Dielectric Film Dense Wavelength Division Multiplexer Filter

technical field

The invention relates to a dense wavelength division multiplexer filter, in particular to an improvement of a dielectric film type dense wavelength division multiplexer filter structure.

Background technique

The dense wavelength division multiplexing device is the core component of the wavelength division multiplexing system, and its characteristics determine the performance of the whole system to a large extent. According to different manufacturing methods, DWDM devices can be divided into several types, and dielectric film DWDM is one of them. This type of dense wavelength division multiplexer uses the filtering effect of multilayer films to multiplex and demultiplex, so the dielectric thin film filter is its most basic component. The passband and stopband width of the filter determine the wavelength range of the multiplexing channel, which affects the minimum channel spacing, and the minimum channel spacing is an important factor determining the maximum number of multiplexing channels of the dense wavelength division system. In principle, the higher the multiplexing number allowed by the DWDM system, the lower the communication cost. Therefore, making a broadband filter with excellent performance is extremely important for increasing the multiplexing number of the wavelength division multiplexing system.

In the prior art, there are dielectric film type wavelength division multiplexing filters made by various methods, such as a multilayer dielectric film type wavelength division multiplexing filter disclosed in "All Optical Network" (Zhang Baofu et al., People's Posts and Telecommunications Press, 2000.1). The device uses two rod lenses whose refractive index is gradually distributed to form a parallel optical path, and inserts a light-splitting dielectric film into the two 1/4 pitch rod lenses of the parallel optical path to form a filter. This filter is a primary wavelength division multiplexer, which can only realize the interval width below 200GHZ. In the structural design of 100GHZ and 200GHZ wavelength division multiplexing filters, three-cavity filters are mostly used. Such as the design of Sub/(HL) ⁶ H6L(HL) ¹⁴ 4L(LH) ¹⁴ 6L(HL) ⁶ H/air, the accompanying drawing 7 of the spectral characteristics. There are ripples in the passband range of the spectral filter, which is commonly referred to as the rabbit ear effect. At the same time, the transition part between the cut-off wavelength region and the passband region of this design is not steep enough, which affects the isolation of different signals (there is signal cross-winding). In addition, optical periodic gratings and Bragg gratings can also be used to form broadband filters. The dense wavelength division multiplexer with Bragg grating structure is currently in the laboratory research stage, and it is not yet practical and industrialized. However, due to the need to make full use of the existing cables to reduce the passband interval and increase the number of multiplexes, it is becoming more and more difficult to manufacture broadband filters for wavelength division multiplexers with excellent performance.

Contents of the invention

The technical problem of the present invention is to overcome the deficiencies of the prior art and provide a dielectric film type dense wavelength division multiplexer filter that can increase the number of channels, has wide bandwidth and excellent performance.

One of the technical solutions of the present invention is: a dielectric film type dense wavelength division multiplexing filter, its structure is:

Sub/(HL) ^N1 H8L(HL) ⁸ HL(HL) ^N2 H6L(HL) ⁹ HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air

In the formula, Sub is the substrate material, Air is the incident medium air, the film coefficient of the dielectric film is N1=8~11, N2=9~11, H is Ta ₂ O ₅ (tantalum pentoxide), L is SiO ₂ (di Silicon oxide), 0.404H1.21L is the anti-reflection film layer structure added on the air side, the anti-reflection film layer material adopts the same material as the main film system structure, that is, H is tantalum pentoxide Ta ₂ O ₅ , L is Silicon dioxide SiO ₂ , these two layers further increase the passband transmittance of the filter, reduce insertion loss, and make the transmission characteristics in the passband smoother.

The optical thicknesses of H and L are (1/4)λ ₀ (λ ₀ =1550 nm), respectively.

The second technical solution of the present invention is: a dielectric film type dense wavelength division multiplexer filter, its structure is;

Sub/(HL) ^N3 H6L(HL) ⁸ HL(HL) ⁹ H6L(HL) ^N4 HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air

In the formula, Sub is the substrate material, Air is the incident medium air, H is Ta ₂ O ₅ (tantalum pentoxide), L is SiO ₂ (silicon dioxide), the film coefficient of the dielectric film is N3=8～12, N4= 9-11, 0.404H1.21L layer is anti-reflection film structure, anti-reflection film layer material adopts the same material as the main film system structure, that is, H is tantalum pentoxide Ta ₂ O ₅ , L is silicon dioxide SiO ₂ . These two layers further increase the passband transmittance of the filter, reduce insertion loss, and make the transmission characteristics in the passband smoother.

The optical thicknesses of H and L are (1/4)λ ₀ (λ ₀ =1550 nm), respectively.

Compared with the prior art, the present invention has the following advantages:

1. The structure of the present invention is four chambers, while the existing structure is three chambers;

2. The four-cavity filter has a better rectangular filter passband, which improves the passband effect and reduces insertion loss;

3. The structure of the present invention adds an outer anti-reflection film to smooth the passband of the filter and eliminate the rabbit ear effect of the existing structure.

4. Through the reasonable structural design of the dielectric film dense wavelength division multiplexer filter and the correct control of the film thickness, a filter with excellent performance is provided for the wavelength division multiplexer with a channel spacing of 50 GHz. At the same time, the communication cost is reduced.

Description of drawings

Fig. 1 is the structural representation of embodiment 1 of the present invention;

Fig. 2 is the characteristic curve of embodiment 1 of the present invention;

Fig. 3 is the structural representation of embodiment 2 of the present invention;

Fig. 4 is the characteristic curve of embodiment 2 of the present invention;

FIG. 5 is a schematic structural view of Embodiment 3 of the present invention;

Fig. 6 is a characteristic curve of embodiment 3 of the present invention.

Fig. 7 shows the design spectral transmittance of the existing three-cavity filter.

Detailed ways

Embodiment 1 of the present invention is a band-pass filter with all-dielectric film. Its structure is shown in Figure 1. The filter is alternately composed of two dielectric materials with a higher refractive index and a lower refractive index. The higher refractive index The dielectric material H is Ta ₂ O ₅ (tantalum pentoxide), and its refractive index n _H =2.05˜2.06; the lower refractive index dielectric material L is SiO ₂ (silicon dioxide), and its refractive index n _L =1.46. The optical thicknesses of H and L are respectively (1/4)λ ₀ , where λ ₀ is the central wavelength of the filter, such as λ ₀ =1550nm. The all-dielectric filter is basically the same as the Fabry-Perot etalon with a dielectric reflection film, so the analysis of the Fabry-Perot filter is also applicable to the case of the all-dielectric filter, so the Fabry-Perot etalon is used The channel spacing and the half-width of the passband are calculated from the characteristic analysis formula of the Li-Pello filter. Since the transmission curve of a simple all-dielectric Fabry-Perot filter is not an ideal shape, a structure is designed as:

Sub/(HL) ⁸ H8L(HL) ⁸ HL(HL) ⁹ H6L(HL) ⁹ HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air Full Dielectric film filter, where H is Ta ₂ O ₅ (tantalum pentoxide), L is SiO ₂ (silicon dioxide), N ₁ =8, N ₂ =9, by correctly controlling the film thickness, the desired The characteristic curve is shown in Fig. 2, the half-width of its passband is 2Δλ=0.72nm, and the channel interval of the corresponding dense wavelength division multiplexer is Δf=50GHz.

The filter uses the SPECTOR coating machine of Veeco/Ion Tech.Inc company, adopts ion beam sputtering technology, the substrate rotates at high speed, the rotation speed is 1200 rpm, and the light source used for film thickness monitoring is a laser light source with good monochromaticity. Light source monochromaticity Δλ/λ<1/10000. The signal-to-noise ratio of the optical signal is better than 10 ⁵ . All film thicknesses are monitored once by means of transmission.

As shown in Figure 3, Embodiment 2 of the present invention is also an all-dielectric bandpass filter, and its structure is:

Sub/(HL) ¹¹ H8L(HL) ⁸ HL(HL) ⁹ H6L(HL) ⁹ HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air

In the formula, H is Ta ₂ O ₅ (tantalum pentoxide), L is SiO ₂ (silicon dioxide), N ₁ =11, N ₂ =9, H and L have (1/4)λ ₀ optical Thickness, λ ₀ is the center wavelength of the filter, λ ₀ =1550nm. The characteristic curve of the filter is shown in Fig. 4, the half-width of the passband is 2Δλ=0.72nm, and the channel interval of the corresponding dense wavelength division multiplexer is Δf=50GHz.

The filter uses the SPECTOR coating machine of Veeco/Ion Tech.Inc company, adopts ion beam sputtering technology, the substrate rotates at high speed, the rotation speed is 1200 rpm, and the light source used for film thickness monitoring is a laser light source with good monochromaticity. Light source monochromaticity Δλ/λ<1/10000. The signal-to-noise ratio of the optical signal is better than 10 ⁵ . All film thicknesses are monitored once by means of transmission.

As shown in Figure 5, the structure of Embodiment 3 of the present invention is:

Sub/(HL) ⁸ H6L(HL) ⁸ HL(HL) ⁹ H6L(HL) ⁹ HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air

In the formula, H is Ta ₂ O ₅ (tantalum pentoxide), N ₁ =8, N ₂ =9 filter, L is SiO ₂ (silicon dioxide), and the optical thicknesses of H and L are (1/4 )λ ₀ , where λ ₀ is the central wavelength of the filter, the characteristic curve of the filter is shown in Figure 6, the half width of the passband is 2Δλ=0.72nm, and the channel interval of the corresponding dense wavelength division multiplexer is Δf=50GHz. The filter uses the SPECTOR coating machine of Veeco/Ion Tech.Inc company, adopts ion beam sputtering technology, the substrate rotates at high speed, the rotation speed is 1200 rpm, and the light source used for film thickness monitoring is a laser light source with good monochromaticity. Light source monochromaticity Δλ/λ<1/10000. The signal-to-noise ratio of the optical signal is better than 10 ⁵ . All film thicknesses are monitored once by means of transmission.

Claims (4)

1. A dielectric film type dense wavelength division multiplexer filter is characterized in that: the structure of the dielectric film layer is: Sub/(HL) ^N1 H8L(HL) ⁸ HL(HL) ^N2 H6L(HL) ⁹ HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air In the formula, H is tantalum pentoxide Ta ₂ O ₅ , L is silicon dioxide SiO ₂ , 0.404H1.21L is the layered anti-reflection film added on the air side, Sub is the substrate material, Air is the incident medium air, The film layer coefficient N1=8-11 of the dielectric film, and N2=9-11 are the period numbers of the corresponding dielectric film stack. 2. dielectric film type dense wavelength division multiplexer filter according to claim 1, is characterized in that: described anti-reflection film layer material has adopted the same material with main film system structure, and namely H is tantalum pentoxide Ta ₂ O ₅ , L is silicon dioxide SiO ₂ . 3. A dielectric film type dense wavelength division multiplexer filter, characterized in that: the structure of the dielectric film layer is: Sub/(HL) ^N3 H6L(HL) ⁸ HL(HL) ⁹ H6L(HL) ^N4 HL(HL) ⁹ H4L(HL) ⁹ HL(HL) ⁸ H2L(HL) ⁸ H0.404H1.21L/Air In the formula, H is Ta ₂ O ₅ tantalum pentoxide, L is SiO ₂ silicon dioxide, 0.404H1.21L is the anti-reflection film layer structure added on the air side, Sub is the substrate material, Air is the incident medium air, The film layer coefficient N1=8-11 of the dielectric film, and N2=9-11 are the period numbers of the corresponding dielectric film stack. 4. dielectric film type dense wavelength division multiplexer filter according to claim 3, is characterized in that: described anti-reflection film layer material has adopted the same material with main film system structure, and promptly H is tantalum pentoxide Ta ₂ O ₅ , L is silicon dioxide SiO ₂ .

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