CN1160893C - Interleaver wavelength division multiplexer (Interleaver) - Google Patents

Abstract

The present invention relates to an interleaver which is composed of an optical fiber collimation coupler and a solid cavity Fabry-periot comb optical filter, wherein by using the selective transmission and reflection functions of discrete wavelengths with fixed intervals of the comb filter, crossed wavelengths are separated, and optical signals of odd-numbered channels (lambda 1, lambda 3, lambda 5, etc.) and optical signals of even-numbered channels (lambda 2, lambda 4, lambda 6, etc.) are separated to realize the wavelength division multiplex function to the crossed wavelengths; on the basis, a plurality of interleaver units are connected to form a multi-stage interleaver device. The DWDM wavelength intervals with high density pass through one or multiple stages of interleavers, which can expand the wavelength intervals of the channels.

Description

Interleaver wavelength division multiplexer (Interleaver)

technical field

The invention relates to a passive device used in a Dense Wavelength Division Multiplexing (DWDM) optical fiber communication system, which is used for multiplexing or demultiplexing DWDM multi-wavelength optical signals according to cross-wavelength separation, so as to expand DWDM wavelength channels interval, reducing the difficulty of wavelength multiplexing.

Background technique

The all-optical communication network based on DWDM will become an important cornerstone of the modern information society, and it is the only technical way to meet the development speed of Internet network capacity doubling every six months. DWDM device is one of the keys to realize all-optical communication. With the increase of wavelength multiplexing density, the interval between adjacent wavelengths is continuously reduced, which brings considerable difficulty to the device manufacturing process. People come up with different solutions for this. The prior art of using Fabry-Perot filters to form wavelength division multiplexers can be found in the patents "Fabry-Perot Fabry-Perot Filter Array Wavelength" proposed by Jayaraman et al. in 1998 and 2000 Demultiplexer (US Patent: 6,122,417; US Patent: 5,835,517)" and the patent proposed by Halbout, et al. "Optical Demultiplexer for Passive Selection of Multiplexed Optical Wavelengths (US Patent: 5,408,319)". The former uses the combination of the array self-focusing lens and the array Fabry-Perot Fabry-Perot filter for wavelength division multiplexing, and selects the filter wavelength by adjusting the cavity length of the Fabry-Perot Fabry-Perot resonant cavity; the latter The other is to place a silicon chip between the two cavity surfaces of the Fabry-Perot resonant cavity, and adjust the filter wavelength by means of electric heating. A common feature of these patents is the use of the traditional discrete Fabry-Perot cavity mirror structure, so the stability of the device is difficult to guarantee, and the filter center wavelength needs to be dynamically adjusted, which limits the application in practical devices.

Contents of the invention

The object of the present invention is to provide a wavelength division multiplexing device with good stability, which adopts solid cavity Fabry. Bailuo Fabry-Perot comb filter technology separates high-density wavelength intervals into low-density wavelength intervals by separating cross wavelengths; at the same time, the device is easy to cascade, so that the final channel spacing and channel width requirements of DWDM can be reduced.

The interleaved wavelength division multiplexer (Interleave) that realizes the object of the present invention is made up of fiber optic collimator coupler and comb optical filter, comprises two passages, and the input dual-fiber ferrule of the first passage comprises incident optical fiber and reflective optical fiber, optical fiber The end face is placed on the focal plane of the collimating coupling lens, and then the optical path is sequentially connected to the comb filter, the focusing coupling lens and the output fiber ferrule; the reflection fiber of the first channel input double fiber ferrule is connected to the input fiber of the second channel Then the optical path connects the collimating coupling lens, comb filter, focusing coupling lens and output fiber ferrule of the second channel in turn. The incident fiber of the first channel dual-fiber ferrule and the output fibers of the two channels form a three-port device.

The comb-shaped optical filters of the two channels are composed of solid cavity Fabry-Bailuo Fabry-Perot etalons, and each center transmission wavelength of the second channel comb-shaped optical filters is relative to that of the first channel comb-shaped optical filters. There is a shift in channel wavelength spacing. The Fabry-Perot etalon is formed by coating a dielectric reflection film on both surfaces of a flat plate of optical material to form a Fabry-Perot cavity. In order to realize the approximately rectangular optical filter passband required by DWDM, the comb optical filters of the two channels are optically bonded by 2 to 5 Fabry-Perot etalons with the same central wavelength.

Using the three-port device as a single-stage cross-wavelength wavelength division multiplexing unit, it can be cascaded to form a multi-stage cross-wavelength wavelength division multiplexing device, that is, the two output channels of the first-stage three-port device are respectively connected to the two second Level three-port devices are connected by optical paths to form five-port devices; by analogy, more levels of cross-wavelength wavelength division multiplexing devices can be formed.

The main features of the present invention are: (1) adopting the Fabry-Perot Fabry-Perot comb filter of solid cavity structure, the central wavelength is guaranteed by the fixed cavity length of the solid cavity optical material without adjustment, so the performance is stable, Can realize passive work; (2) the proposed solid cavity Fabry-Bailuo Fabry-Perot comb filter structure is convenient for cascading of multiple filters, and realizes the approximately rectangular filter passband required by DWDM devices; (3) ) using two channels with interleaved central transmission wavelengths to realize the cross-wavelength separation of DWDM optical signals, so that the isolation ratio of the two channels is guaranteed at the same time; Requirements are reduced.

Description of drawings

Fig. 1 represents the structure of three-port device of the present invention,

Figure 2 shows a five-port device composed of a cascade of single-stage three-port devices,

Figure 3 shows the fixed cavity Fabry-Perot Fabry-Perot etalon structure,

Figure 4 is a multi-cavity optical filter composed of multiple Fabry-Perot etalons glued together,

Fig. 5 shows output signal spectra of two channels of the device of the present invention.

Detailed ways

The single-stage Interleaver unit structure shown in Fig. 1 contains two channels, the optical fiber 11 of the first channel double-fiber ferrule 13 is connected with the optical path of the coupling lens 14, and then the comb optical filter 15, the coupling lens 16 and the optical fiber are connected in sequence Ferrule 17; the reflective fiber 12 of fiber optic ferrule 13 is connected to the fiber optic ferrule 23 of the second channel, and then connected with coupling lens 24, and then connected with comb optical filter 25, coupling lens 26 and fiber optic ferrule 27 in sequence, form a three-port device. The DWDM multi-wavelength optical signal (λ ₁ -λ _m ) input by the optical fiber 11 of the optical fiber ferrule 13 is collimated by the coupling lens 14 and enters the comb optical filter 15, and the odd wavelength channels (λ ₁ , λ ₃ , λ ₅ ...) the optical signal passes through the comb filter 15, is focused into the fiber ferrule 17 by the coupling lens 16, _{and is} output by the optical fiber 18 (channel ₁ ); The signal is reflected by the comb optical filter 15, and enters the comb optical filter 25 through the coupling lens 14, the reflection optical fiber 12 of the optical fiber ferrule 13 and the coupling lens 24, and each central transmission wavelength of the comb filter 25 is relatively The device 15 moves a channel wavelength interval, so the optical signals of the even-numbered wavelength channels (λ ₂ , λ ₄ , λ ₆ ...) will pass through the comb optical filter 25, be focused by the coupling lens 26 and enter the optical fiber ferrule 27, and be transmitted by the optical fiber 28 output (channel 2). This achieves the separation of odd wavelength channels (channel 1) and even wavelength channels (channel 2). The output wavelength channel spacing of the two channels is doubled compared with the input DWDM wavelength spacing.

Figure 2 shows a multi-stage Interleaver device structure, which is formed by cascading a plurality of Interleaver units as shown in Figure 1, that is, two output channels (2, 3) of the first-level Interleaver (1) are respectively connected to the second Stage Interleaver (4, 5), then the output wavelength channel spacing of the four output channels (6, 7, 8, 9) of the second stage Interleaver will increase by four times compared with the input DWDM wavelength spacing. For example, 50GHz is separated into 100GHz, and then 100GHz is separated into 200GHz. Because the optical filter with 200GHz wavelength interval has been commercialized at present, it is possible to apply the current mature DWDM device to realize high-density wavelength multiplexing. By analogy, more levels of Interleaver devices can be formed.

The comb optical filter described in the above-mentioned Interleaver is composed of a solid cavity Fabry-Perot (Fabry-Perot) filter. As shown in Figure 3, reflective film (32,33) is plated on two surfaces of a precision-processed optical material flat plate (31) to form a Fabry-Bailuo Fabry-Perot cavity, which is made by precision optical processing. The thickness of the optical plate (that is, the cavity length of the Fabry-Perot cavity) meets the condition that the free spectral region of the filter is equal to twice the wavelength interval of the DWDM channel, and the required comb-shaped optical filtering can be realized . The thickness d of the optical flat plate is determined by the following formula:

$\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; ;</span>$ $\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&delta;\&lambda;</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

In the formula, n is the refractive index of the material, θ is the light incident angle, m is the Fabry-Perot cavity interference order, _λ0 is the center wavelength, and δλ is the DWDM channel spacing. Design example: δλ=0.8nm, n=1.47, λ ₀ =1550nm, θ=0, calculated: d=510.21μm

In order to realize the approximately rectangular optical filter passband required by DWDM devices, multiple Fabry-Perot filters (A, B, C, D...) can be used for optical filtering according to the structure shown in Figure 4. glued to form a multi-cavity filter.

Fig. 5 shows the output signal spectra of two channels of an Interleaver designed by the present invention, which adopts a Fabry-Perot comb filter with a four-cavity structure as a wave splitting element. The solid line in the figure represents the output passband spectrum of channel 1. The center wavelength of the DWDM composite wavelength channel is at the peak and valley of the curve respectively, and the optical signal at the peak wavelength is transmitted (λ ₁ , λ ₃ , λ ₅ ...), Optical signals at valley wavelengths are reflected (λ ₂ , λ ₄ , λ ₆ ...). The dotted line represents the output passband spectrum of channel 2. The central wavelength of the passband is shifted by a channel wavelength interval relative to the passband 1, and the reflected optical signals (λ ₂ , λ ₄ , λ ₆ ...) of the passband 1 are transmitted. At the same time, the optical signals (λ ₁ , λ ₃ , λ _{5 .} . . ) serially inserted into channel 2 from channel 1 are reflected, thus ensuring a high degree of optical signal isolation.

Claims (4)

1. A cross-wavelength wavelength division multiplexer is made up of an optical fiber collimator coupler and a comb filter, characterized in that: (1) The cross-wavelength wavelength division multiplexer is composed of two channels, the input double-fiber ferrule of the first channel includes an incident optical fiber and a reflective optical fiber, and the end face of the optical fiber is placed on the focal plane of the collimating coupling lens, and then sequentially The optical path is connected to the comb filter, focusing coupling lens and output fiber ferrule; the reflection fiber of the first channel input double fiber ferrule is connected to the input fiber ferrule of the second channel, and then the optical path is connected to the collimated coupling of the second channel in turn Lens, comb filter, focusing coupling lens and output fiber ferrule, the incident fiber of the first channel double fiber ferrule and the output fiber of the two channels constitute a three-port device, (2) The comb-shaped optical filters of the two channels are made of solid cavity Fabry-Bailuo Fabry-Perot etalon, and each center transmission wavelength of the second channel comb-shaped optical filters is relative to the first channel comb-shaped optical filter. Optical filters have a channel wavelength spacing shift. 2. cross-wavelength wavelength division multiplexer as claimed in claim 1, it is characterized in that the Fabry-Bai Luo Fabry-Perot etalon of the comb filter of described two channels is to pass through on an optical material flat plate The two surfaces of the optical plate are coated with a dielectric reflection film and form a Fabry-Perot cavity. The thickness d of the optical flat plate is determined by the following formula: $\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; ;</span>$ $\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&delta;\&lambda;</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}$ In the formula, n is the refractive index of the optical material, θ is the light incident angle, m is the Fabry-Perot cavity interference order, _λ0 is the central wavelength, and δλ is the DWDM channel spacing. 3. cross-wavelength wavelength division multiplexer as claimed in claim 2, is characterized in that the comb filter of described two passages is made of 2～5 Fabry-Bailuo Fabry-Perot standard of same central wavelength The tool is optically bonded to realize the rectangular optical filter passband required by DWDM. 4. The cross-wavelength wavelength division multiplexer as claimed in claim 1, 2 or 3, characterized in that: the three-port device is used as a single-stage cross-wavelength wavelength-division multiplexing unit, which can be cascaded to form a multi-stage cross-wavelength Wavelength division multiplexing device, that is, the two output channels of the first-level three-port device are respectively connected with the optical paths of two second-level three-port devices to form a five-port device; and so on, more levels of cross-wavelength wavelength division can be formed. Multiplexing devices.

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