CN101562494B - Optical time division multiplexer and manufacturing method - Google Patents

Abstract

An optical time-division multiplexer is composed of multi-stage Whiteman interferometers, each stage of Whiteman interferometer is composed of optical fiber pigtails, self-focusing lenses, and spectroscopic films; the coupling of optical fiber pigtails and self-focusing lenses constitutes optical fiber collimation lenses; A spectroscopic film is coated on the end face of the fiber collimating lens; a pair of fiber collimating lenses coated with a spectroscopic film is used to form a fiber optic splitting device; two such fiber optic splitting devices constitute the first stage of the Whiteman interferometer; each stage of the Whiteman The interferometer can double the optical signal rate by properly adjusting the length difference of the interference arm, and the n-level Whiteman interferometer can increase the optical signal rate by n times, n=1, 2, 3, 4...; The beneficial effect of the present invention is based on the improvement of the shortcomings of the traditional time division multiplexer. Compared with the time division multiplexer of foreign companies, the present invention is superior to foreign products in terms of loss, wavelength flatness, polarization sensitivity, and temperature stability. Moreover, the production cost is low and has great commercial value.

Description

Optical time division multiplexer and manufacturing method thereof

technical field

The invention relates to an optical time division multiplexer and a manufacturing method, belonging to the field of information technology.

Background technique

A substantial increase in communication capacity is an inevitable trend in the development of an information society, and Optical Time Division Multiplexing (OTDM) and Dense Wavelength Division Multiplexing (DWDM) are two important and effective ways to increase optical fiber communication capacity. OTDM technology and DWDM technology are two different technical routes to realize future high-speed, large-capacity optical fiber communication system, and a large-capacity optical fiber communication system can be constructed by using either technology alone. The combination of OTDM technology and DWDM technology can make full use of the advantages of these two technologies and discard their shortcomings, and jointly build the future of high-speed and large-capacity optical fiber communication systems.

While some developed countries are actively promoting the practical application of DWDM optical communication systems, they are also actively promoting the development of 0TDM optical communication systems. June 19, 2007--British network operator JANET announced that it has achieved single-channel 40Gbps transmission for both the transport layer and the IP layer. Easier, JANET says they work with Ciena and Verizon Business at the transport level, and with Alcatel-Lucent and Juniper at the IP level. Japan has shown a positive attitude towards ultra-high-speed OTDM technology. The Japan Postal Service entrusted NTT Corporation to realize 640Gbit/s OTDM transmission experiments using ring fiber mode-locked lasers. 80ch) DWDM/OTDM hybrid optical communication system, and claims that the commercial DWDM/OTDM communication system representing the highest level will be launched soon. In recent years, my country has already had a network demand of 40Gbit/s, and there will be a demand for 160Gbit/s in the future. In view of the fact that OTDM technology is an effective way to develop a super-large-capacity transmission network, the OTDM communication system is based on high-speed optical signal processing technology, and the future The all-optical network is fully compatible and has great development prospects.

The optical time division multiplexer is the core device of OTDM technology, and only the optical time division multiplexer with excellent performance can guarantee the signal quality after multiplexing. The currently reported optical time division multiplexers are all Mark-Zehnder interferometer (M-Z) type structures (Mike J, O'Mahony et al., IEEE Communications Magazine, December1995, 82-88), (Wei Daoping et al., Optical Communications Research, No. 2, 1999, 43-47). This M-Z interferometer is made up of light-splitting device and delay device, and light-splitting device is divided into again: (1) planar waveguide type (Jepsen, K.S. et al., Conference on Optical Fiber Communication, Technical DigestSeries, 1998, p 310-311), when The adjustability of the extension device is good, but the insertion loss is large and the price is expensive; (2) Fused taper fiber coupler type (Hui Zhanqiang et al., Science Technology and Engineering, Volume 8, No. 17, September 2008, 4999 -5001), the light splitting/combining of the above-mentioned time division multiplexer is completed by the optical coupling generated by the thinned optical fiber. When the temporal/spatial conditions of the light source are satisfied, a strong interference effect is caused, and the amplitude of each optical pulse is not in a stable state, but fluctuates irregularly at all times, especially when shaking the optical fiber at the input end of the optical time division multiplexer , the pulse fluctuation is more significant. The splitting ratio of the fused tapered fiber coupler is a polarization phase difference sensitive device. Under the condition of constant input power, the power of an output branch will change with the change of the input polarization state. The characteristic parameters of each fused tapered fiber coupler are slightly different, and the consistency is poor. The polarization-dependent loss is relatively large, and there is a large first-order polarization mode dispersion (PMD). The wavelength dependence of the splitting ratio is large. After long-term use, the temperature and strain instabilities accumulated by the multi-stage fused-taper fiber coupler will become larger, so that the performance of the above-mentioned multiplexer after being placed for a period of time will change significantly. The situation when it was just completed is very different, and it is difficult to put it into practical use.

Coherence is related to the size of the light source. According to the Huygens-Fresnel theory, the light disturbance on the interference surface is formed by the superposition of secondary waves emitted on a certain surface between this point and the light source. After in-depth analysis and trial and error, it is found that the taper of the fused-taper fiber coupler actually reduces the size of the "light source", which is equivalent to increasing the coherence in terms of spatial coherence; moreover, the sin ² (Cz) splitting characteristics of the fiber coupler The interference sensitivity is exacerbated, and the sin ² (Cz) relationship makes the wavelength flatness poor.

If all optical time division multiplexers use traditional optical devices, the structure is complex and difficult to couple and adjust with optical fibers (refer to: German u2t company optical time division multiplexer product description).

Contents of the invention

In order to overcome the deficiencies of the prior art structure and aim at the problems existing in the above-mentioned structured light time division multiplexer, the present invention innovatively adopts a novel Whiteman type interferometer structured light time division multiplexer combined with an optical fiber and a coated bulk optical device to solve To solve the stability problem of the optical time division multiplexer, the optical time division multiplexer of this structure has not been reported at home and abroad. The invention provides an optical time division multiplexer and a manufacturing method.

The technical solution adopted by the present invention to solve its technical problems is:

An optical time division multiplexer, which is composed of a multi-stage Whiteman interferometer, and a splitting film with a splitting ratio of 1:1 is placed between a pair of optical fiber collimating lenses to form a fiber optic lens type splitting device. The splitting film is of the amplitude splitting type. Without changing the phase, the two above-mentioned fiber optic lens-type spectroscopic devices constitute the first stage of the Whiteman interferometer; each stage of the Whiteman interferometer is composed of a fiber pigtail, a self-focusing lens, and a spectroscopic film; the fiber pigtail and the self-focusing lens are coupled to form an optical fiber Collimating lens; Coating beam-splitting film on the end face of the fiber collimating lens;

The input signal enters the spectroscopic device composed of a self-focusing lens with a pigtail coated with a spectroscopic film and is divided into two parts, one for reflection and one for transmission. The reflected and transmitted signals travel along the two arms formed by the optical fiber. The length of the two arms of the optical fiber is adjusted to meet The frequency multiplication requirement of the signal, when it reaches another optical splitting device connected in reverse, it is synthesized into one signal;

The fiber length difference DL _i of the 1st path and the 2nd path satisfies:

${\mathrm{<span\; class="notranslate">\; DL</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; DT</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ;</span>$

m＝2ⁱ，T₀为时分复用前的脉冲重复周期；每一级怀特曼干涉仪按照

调整第1路和第2路的光纤长度差DL_i，将光信号速率提高一倍；Where c is the transmission speed of light in vacuum; n is the refractive index of the fiber core; the subscript i is the level of the Whiteman interferometer, i=1, 2, 3, 4...;

m=2 ⁱ , T ₀ is the pulse repetition period before time division multiplexing; each stage of Whiteman interferometer follows

Adjust the optical fiber length difference DL _i of the first and second paths to double the optical signal rate;

The connection mode between each stage of Whiteman interferometer and the next stage of Whiteman interferometer is in series; the length of optical fiber is not required, multi-stage Whiteman interferometers are connected, and the n-stage Whiteman interferometer increases the optical signal rate to the original rate. 2 ⁿ times, n=1, 2, 3, 4...;

1. The self-focusing lens with pigtail is coated with spectroscopic film,

Fiber pigtail, self-focusing lens, beam splitting film;

The length of the self-focusing lens is a quarter of a cycle, which can turn non-parallel light into parallel light when it reaches the plane of the beam splitting film. The self-focusing lens is integrated with the fiber pigtail, as shown in Figure 6;

The light-splitting device adopts a light-splitting film with very good consistency to ensure that the light-splitting ratio of each component is 1:1, and the slight difference is corrected by the reciprocal connection between the reflection end and the transmission end;

The spectroscopic film is a commonly used interference spectroscopic film;

2. Whiteman interferometric optical time division multiplexer;

The composition of the first stage of the Whiteman interferometric optical time division multiplexer is shown in Figure 7. The input signal enters the spectroscopic device composed of a self-focusing lens with a pigtail and coated with a spectroscopic film, and is divided into two parts, one for reflection, one for transmission, reflection and The transmitted signal travels along the two arms of the Whiteman interferometer composed of optical fibers. The length of the two arms of the optical fiber is adjusted to meet the signal frequency multiplication requirements. When it reaches another optical splitting device connected in reverse, it is synthesized into one signal;

3. Mark Zehnder type (M-Z type) optical time division multiplexer;

The composition of the first stage of the Mark-Zehnder type optical time division multiplexer is shown in Figure 8. The input signal enters the optical splitting device composed of optical fiber fusion taper and is divided into two parts, one for reflection and one for transmission, and the reflection and transmission signals are formed along the optical fiber The two arms of the Mark Zehnder interferometer move forward, and the length of the two arms of the fiber is adjusted to meet the signal frequency multiplication requirements. When it reaches another optical splitting device connected in reverse, it is synthesized into one signal;

4. Fully polarized M-Z interferometer structured light time division multiplexer;

The composition of the first stage of the full-polarization M-Z optical time division multiplexer is shown in Figure 9. The input signal enters the polarization-maintaining optical splitter composed of polarization-maintaining optical fiber fusion taper and is divided into two parts, one for reflection and one for transmission, and the reflection and transmission signals Go forward along the two arms of the full-polarization M-Z interferometer composed of optical fibers. The length of the two arms of the optical fiber is adjusted to meet the signal frequency doubling requirements. When it reaches another reversely connected polarization-maintaining optical device, it is synthesized into one signal;

Comparing the above three optical time division multiplexers, it can be seen that the Whiteman interference type optical time division multiplexer does not need to fuse and taper the optical fiber, and when it reaches the light splitting position, it is parallel light. The optical path analysis can adopt the ray tracing method; while the M-Z type and the fully polarized M-Z type optical time division multiplexer split the optical fiber fusion tapered light, and realize the light splitting through the electromagnetic field coupling effect caused by the tapered part, and the optical path analysis must use the Maxwell of the electromagnetic field. Equation analysis.

A method for manufacturing an optical time division multiplexer, comprising the step of adopting optical fiber cutting and welding for time delay adjustment; the steps are as follows:

The delay adjustment is realized by controlling the length of the interference arm of the fiber optic interferometer; the fiber is cut with a fiber cutter with a ruler according to the time elongation requirement, and then spliced with a fiber fusion splicer;

The optical pulse of the coupling arm is inserted in the middle of the optical pulse of the through arm;

The steps of delay adjustment are as follows:

The relationship between the change in fiber length ΔL and the pulse shift position Δt is shown in the following formula,

${\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}$

Among them, ΔL represents the change of fiber length, Δt represents the change of pulse moving position, c represents the speed of light in vacuum, which is 3×10 ⁸ m/s, and n represents the refractive index of the fiber core layer;

Calculate the fiber length at the reflection end that needs to be adjusted every time the pulse moves 1 ps on the oscilloscope;

Precisely adjust the delay;

Through the method of coating the collimating lens with splitting film, the slight difference can be adjusted by the microbending stress of the fiber itself, and the amplitude of each level is adjusted in turn to ensure the consistency of the amplitude of each level in the future;

When the time-division multiplexing rate to be achieved is high and the bandwidth of the oscilloscope is not enough, the attenuation of one of the two channels is increased respectively to convert it into the time delay difference of the two low-rate optical pulses observed on the oscilloscope. , then achieve the purpose of equivalent observation of high-rate optical pulses;

After the time delay adjustment is completed, the optical fiber is welded and spliced by an optical fiber fusion splicer, and then heated and packaged with a heat shrinkable tube.

Experimental results show that the time delay accuracy of the present invention reaches 0.007ps, which is better than 1.5 μm, which fully meets the transmission requirements of a single-channel communication rate above 160Gb/s, and the stability of the time delay is also verified in the experiment.

The beneficial effect of the present invention is based on the improvement of the shortcomings of the traditional time division multiplexer. Compared with the time division multiplexer of foreign companies, the present invention is superior to foreign products in terms of loss, wavelength flatness, polarization sensitivity, and temperature stability. Moreover, the production cost is low and has great commercial value.

Description of drawings

Fig. 1 structural representation of optical fiber collimating lens of the present invention;

Fig. 2 is a structural schematic diagram of coating a semi-transparent and semi-reflective film on an optical fiber collimating lens of the present invention;

Fig. 3 is a structural schematic diagram of an optical fiber splitting device of the present invention;

Fig. 4 structural representation of the first-level Whiteman interferometer of the present invention;

Fig. 5 n-level Whiteman interferometer structure schematic diagram of the present invention;

The schematic diagram of the effect of the beam splitter in the optical path of Fig. 6;

Fig. 7 one-stage Whiteman interferometric optical time division multiplexer;

Figure 8M-Z interferometer type optical time division multiplexer;

Figure 9 full polarization M-Z interferometer type optical time division multiplexer;

Figure 10 is a schematic diagram of a self-focusing lens with a pigtail coated with a spectroscopic film; where: a, b, and c are fiber pigtails, Lends is a self-focusing lens, and Q is a spectroscopic film.

Fig. 11 is a schematic diagram of a conventional fused-taper fiber coupler;

Fig. 12 Schematic diagram of first-level multiplexing of Whiteman interferometric optical time division multiplexer;

Fig. 13 Mark Zehnder type (M-Z type) optical time division multiplexer interference model schematic diagram;

Figure 14 All-polarization M-Z interferometer structured light time division multiplexer;

Fig. 15 The optical fiber end face is fired into a lens Whiteman interferometer type optical time division multiplexer;

Figure 16160GHz optical time division multiplexer structure diagram;

Fig. 17 Schematic diagram of 1×4 multiplexing of Whiteman interferometric optical time division multiplexer;

Figure 18 Oscilloscope observation of delay accuracy of 160GHz optical time division multiplexer;

Figure 19 Oscilloscope observation of delay accuracy of 160GHz optical time division multiplexer;

The schematic diagram of the waveform on the oscilloscope in Figure 20;

Figure 21 Schematic diagram of the waveform on the oscilloscope.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Detailed ways

Embodiment 1: As shown in Figure 4, the first-stage Whiteman interference type optical time division multiplexer, when the frequency before multiplexing is 2.5GHz, the frequency after multiplexing is 5GHz, and the self-focusing lens adopts a quarter-pitch with Rod lens for collimating light function. The refractive index distribution of the self-focusing lens is:

n=n ₀ [1-1/2Ar ² ] (1)

In the formula, n ₀ is the refractive index of the glass on the axis, A is the distribution constant, and r is the radius.

Under the paraxial meridional approximation, the ray equation simplifies to

$\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="dx"\; filenames="H2009100833442E00044.png,H2009100833442E00071.png"\; state="\{\{state\}\}">dx</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="dz"\; filenames="H2009100833442E00044.png,H2009100833442E00071.png"\; state="\{\{state\}\}">dz</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Ax</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, x represents the vertical distance from the light to the axis, and z represents the horizontal position starting from the incident end.

Integrating equation (2) and bringing in the boundary conditions, we get:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>& \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>\end{array}\right)\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, x ₀ and θ ₀ are the height and angle of incident light, respectively, x _c and θ _c are the height and angle of outgoing light, and L is the distance traveled by the fiber in the z direction;

Specifically, when the distribution constants of the two lenses used are the same, and the lengths are both P/4, that is, L ₁ =L ₂ =p/4 and A ₁ =A ₂ =A (where P is the pitch), then

$\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

$\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Therefore, the position and angle of the light emitted from the second lens can be obtained from formula (4):

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}& \frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="A"\; filenames="H2009100833442E00061.png"\; state="\{\{state\}\}">A</figure-callout></span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\\ <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]$

Right now

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

At this time, if the axial refractive indices of the two self-focusing lenses are the same, then

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

It can be seen that the light emitted from the second lens and the light incident on the first lens are symmetrical with respect to the optical axis. Place the two lenses side by side with fiber pigtails connected to both ends of the lenses. The lens is actually a semi-transmissive and semi-reflective beam splitter because it is coated with a beam-splitting film; by adjusting the parameters of the coating process, a beam-splitting ratio of 1:1 can be achieved. The combination of lenses with a long distance can combine two optical signals into one signal. Linking two groups of optical mirrors is in the form of Whiteman interferometer, forming a collimated beam-splitting 20GHz optical time division multiplexer;

The difficulty in making an optical time division multiplexer is to precisely control the delay difference so that each optical pulse is inserted in the middle of the previous pulse, and the 5GHz repetition rate requires that the pulses be separated by 200ps. The specific method is as follows: select one signal as a reference, and generate a delay difference of ΔTi with the other;

${\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 400</span>}\mathrm{<span\; class="notranslate">\; ps</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Where m=2,4,8,16; i=1,2,3,4. The corresponding fiber length difference is calculated according to the following formula:

${\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Where C is the transmission speed of light in vacuum, and n is the refractive index of the fiber core;

The delay adjustment is realized by controlling the length of the fiber optic interferometer interference arm. After the optical fiber is cut with a fiber optic cutter with a ruler according to the elongation requirements, it is fused with an optical fiber fusion splicer. Assuming that the original pulse repetition frequency is f ₀ =2.5GHz, in order to form a repetition frequency of 5GHz, the optical pulse of the coupling arm must be inserted in the middle of the optical pulse of the through arm. When the time delay is adjusted, the relationship between the change of fiber length ΔL and the pulse moving position Δt is shown in Equation (8), where ΔL represents the change of fiber length, Δt represents the change of pulse moving position, c represents the speed of light in vacuum, and is 3×10 ⁸ m/s, n represents the refractive index of the fiber core. The ordinary G652 single-mode fiber is used, and the refractive index of the core layer is about 1.443; in this way, the length of the fiber at the reflection end needs to be adjusted by about 0.21 mm for every 1 ps movement of the pulse on the oscilloscope. Using ingenious fiber cutting and splicing technology to precisely adjust the time delay. The method of coating the beam-splitting film on the collimating lens ensures the consistency of the beam-splitting ratio, and the slight difference can be adjusted by the micro-bending stress of the optical fiber itself, as shown in Figures 20 and 21.

The waveform on the oscilloscope in Figure 20 is the 2.5GHz pulse before multiplexing, and the interval between adjacent pulses is 400ps. The waveform in Figure 21 is the 5GHz pulse waveform after the multiplexing of the first-level Whiteman interferometer. The figure shows that the pulse interval becomes 200ps.

After the time delay adjustment is completed, the optical fiber is welded and spliced by an optical fiber fusion splicer, and then heated and packaged with a heat shrinkable tube.

The present invention has the following technical characteristics:

1. The self-focusing lens with pigtail is coated with spectroscopic film as shown in Figure 10 (necessary technical features),

Among them: a, b and c are optical fiber pigtails, Lends is a self-focusing lens, and Q is a beam splitting film.

The self-focusing lens turns non-parallel light into parallel light when it reaches the plane of the beam-splitting film, which meets the requirements of the beam-splitting film on the angle of light, and avoids the need for the fused cone coupler (or waveguide coupler) to thin the optical fiber (or grind the waveguide) for light splitting Intervention is unstable.

After the self-focusing lens is integrated with the fiber pigtail, it overcomes the problem that the traditional bulk optical interferometer is difficult to couple with the fiber.

The light-splitting device adopts a light-splitting film with very good consistency to ensure that the light-splitting ratio of each component is 1:1, and the slight difference is corrected by the reciprocal connection of the reflection end and the transmission end.

The splitting film is designed to be polarization-independent, which is different from the wavefront splitting method of the fused-taper fiber coupler (or waveguide coupler). The stability of this kind of time division multiplexer is better than that of the former. The spectroscopic film process can realize broadband flat splitting, and the wavelength dependence in the transmission bandwidth is very small. The process of spectroscopic film device is mature, and the temperature stability is good. A schematic diagram of a traditional fused-taper fiber coupler is shown in Fig. 11 .

2. Whiteman interferometric optical time division multiplexer as shown in Figure 12 (necessary technical features);

The Whiteman interferometric optical time division multiplexer consists of multiple stages. Each stage can increase the optical signal rate by n times, n=1, 2, 3, 4....

The interference disturbance of the Whiteman type optical time division multiplexer mainly comes from the self-coherence of the wave field, which belongs to the amplitude division type interference device, which is different from the fused-taper fiber coupler type and the waveguide type M-Z interferometer type optical time division multiplexer.

3. The schematic diagram of the interference model of the Mark-Zehnder type (M-Z type) optical time division multiplexer is shown in Figure 13;

The fully polarized M-Z interferometer structured light time division multiplexer is shown in Figure 14;

4. Delay adjustment adopts the method of fiber cutting and fusion (non-essential technical features)

Experimental results show that the time delay precision of the present invention reaches 0.007ps, that is, better than 1.5 μm, and the stability of time delay is also verified in the experiment.

Embodiment 2: The following structures all belong to the scope of the patent requirements:

(1) The end face of the optical fiber is fired into a lens shape by various heating methods to turn the light into parallel light; a pair of such devices are placed between a pair of splitting films or splitting sheets of various splitting ratios to form a fiber optic lens type Whiteman Interferometer optical division multiplexer, as shown in Figure 15. H1...H4 in Fig. 15 represent 4 sets of components cascaded. 2 sets, 4 sets, ..., 2n sets (n=1, 2, ∞) all belong to the scope of this patent.

(2) The self-focusing lens with pigtails is coated with a spectroscopic film to form an optical fiber self-focusing rod-lens type Whiteman optical fiber interferometer optical division multiplexer, as shown in Figure 16.

Figure 16 above shows the optical division multiplexer of the 4-stage Whiteman fiber interferometer. Level 1, level 2, ..., level n (n=1, 2, ∞) all belong to the scope of this patent.

Both Figure 15 and Figure 16 are Whiteman fiber interferometers composed of "1×2" (or "2×1") devices. The Whiteman fiber interferometer composed of "1×n" (or "n×1") also falls within the scope of this patent. For example, the "1×4" fiber self-focusing rod lens type Whiteman fiber interferometer shown in Figure 17.

Example 3:

The self-focusing lens adopts a quarter-pitch rod lens with the function of collimating light. The refractive index distribution of the self-focusing lens is:

n=n ₀ [1-1/2Ar ² ] (1)

In the formula, n ₀ is the refractive index of the glass on the axis, A is the distribution constant, and r is the radius.

Under the paraxial meridional approximation, the ray equation simplifies to

$\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="dx"\; filenames="H2009100833442E00044.png,H2009100833442E00071.png"\; state="\{\{state\}\}">dx</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="dz"\; filenames="H2009100833442E00044.png,H2009100833442E00071.png"\; state="\{\{state\}\}">dz</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Ax</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, x represents the vertical distance from the light to the axis, and z represents the horizontal position starting from the incident end.

Integrate (2) and bring into the boundary conditions to get:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>& \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>& \mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>\end{array}\right)\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula, x ₀ and θ ₀ are the height and angle of incident light, respectively, x _c and θ _c are the height and angle of outgoing light, and L is the distance traveled by the fiber in the z direction.

Specifically, when the distribution constants of the two lenses used are the same, and the lengths are both P/4, that is, L ₁ =L ₂ =p/4 and A ₁ =A ₂ =A (where P is the pitch), then

$\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

$\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Therefore, the position and angle of the light emitted from the second lens can be obtained from formula (4):

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}& \frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\\ <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="A"\; filenames="H2009100833442E00061.png"\; state="\{\{state\}\}">A</figure-callout></span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)\left(\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}& \frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}}\\ <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; A</span>}}& \mathrm{<span\; class="notranslate">\; 0</span>}\end{array}\right)\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]$

Right now

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

At this time, if the axial refractive indices of the two self-focusing lenses are the same, then

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

It can be seen that the light emitted by the second lens and the light incident by the first lens are symmetrical with respect to the optical axis. Place the two lenses side by side with fiber pigtails connected to both ends of the lenses. The lens is actually a half-transparent mirror because it is coated with a light-splitting film. By adjusting the parameters of the coating process, a splitting ratio of 1:1 can be achieved. Due to the reversibility of the optical path, the combination of two lenses with a length of 1/4 pitch can combine two optical signals into one signal. The combined lens constitutes a Whiteman interferometer whose beam-splitting film splits the amplitude of the light wavefield in two. When the incident light pulse repetition frequency is 10GHz, four Whiteman interferometers are connected in series to form a collimated beam-splitting 160GHz optical time division multiplexer.

The difficulty in making an optical time division multiplexer lies in the precise control of the delay difference, so that each optical pulse is inserted in the middle of the previous pulse, and the 160GHz repetition frequency requires that the pulses be separated by 6.25ps. The specific method is as follows: select one signal as a reference, and generate a delay difference of ΔTi with the other signal.

${\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; ps</span>}}{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Where m=2,4,8,16; i=1,2,3,4. The corresponding fiber length difference is calculated according to the following formula:

${\mathrm{<span\; class="notranslate">\; \&Delta;\; L</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Where C is the transmission speed of light in vacuum, and n is the refractive index of the fiber core.

The delay adjustment is realized by controlling the length of the fiber optic interferometer interference arm. After the optical fiber is cut with a fiber optic cutter with a ruler according to the elongation requirements, it is fused with an optical fiber fusion splicer. Assuming that the original pulse repetition frequency is f ₀ =10 GHz, in order to form a repetition frequency of 20 GHz, the optical pulse of the coupling arm must be inserted in the middle of the optical pulse of the through arm. When the time delay is adjusted, the relationship between the change of fiber length ΔL and the pulse moving position Δt is shown in Equation (8), where ΔL represents the change of fiber length, Δt represents the change of pulse moving position, c represents the speed of light in vacuum, and is 3×10 ⁸ m/s, n represents the refractive index of the fiber core. The ordinary G652 single-mode fiber is used, and the refractive index of the core layer is about 1.443; in this way, the length of the fiber at the reflection end needs to be adjusted by about 0.21 mm for every 1 ps movement of the pulse on the oscilloscope. Using ingenious fiber cutting and splicing technology to precisely adjust the time delay. The method of coating the beam-splitting film on the collimating lens ensures the consistency of the beam-splitting ratio, and the slight difference can be adjusted by the micro-bending stress of the fiber itself. The amplitude of each level is adjusted in turn to ensure the consistency of the amplitude of each level in the future. In production, when the bandwidth of the oscilloscope is not enough, the multiplexed pulses cannot be observed. A clever method is adopted. When the fourth stage is multiplexed, the attenuation of one of the two channels is increased, so that it can be converted into observations on the oscilloscope separately. Two 80GHz optical pulses can achieve the purpose of equivalent observation of 160GHz optical pulses, as shown in Figures 18 and 19.

The waveforms on the oscilloscope are the 1st, 3rd, 5th, ..., 15th channels of the 160GHz pulse, and the waveforms below are the 2nd, 4th, 6th, ..., 16th channels of the 160GHz pulse. Δ=6.243ps is shown in , so the precision of the time division multiplexer made by fiber cutting and fusion splicing is 0.007ps, which is better than 1.5μm, fully meeting the 160Gb/s transmission requirements.

After the time delay adjustment is completed, the optical fiber is fused by using an optical fiber fusion splicer, and then heated and packaged with a heat shrinkable tube.

Claims (3)

1. An optical time division multiplexer, characterized in that: Composed of multi-stage Whiteman interferometers, a splitting film with a splitting ratio of 1:1 is placed between a pair of fiber collimating lenses to form a fiber lens type splitting device. The splitting film is of the amplitude splitting type, and the phase does not change when splitting. The lens-type spectroscopic device constitutes the first stage of the Whiteman interferometer; each stage of the Whiteman interferometer is composed of a fiber pigtail, a self-focusing lens, and a spectroscopic film; the coupling of the fiber pigtail and the self-focusing lens constitutes a fiber collimator lens; The end surface of the lens is coated with spectroscopic film; The input signal enters the spectroscopic device composed of a self-focusing lens with a pigtail coated with a spectroscopic film and is divided into two parts, one for reflection and one for transmission. The reflected and transmitted signals travel along the two arms formed by the optical fiber. The length of the two arms of the optical fiber is adjusted to meet The frequency multiplication requirement of the signal, when it reaches another optical splitting device connected in reverse, it is synthesized into one signal; The fiber length difference DL _i of the 1st path and the 2nd path satisfies: ${\mathrm{<span\; class="notranslate">\; DL</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; DT</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\frac{\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ;</span>$ Where c is the transmission speed of light in vacuum; n is the refractive index of the fiber core; the subscript i is the level of the Whiteman interferometer, i=1, 2, 3, 4...;

m=2 ⁱ , T ₀ is the pulse repetition period before time division multiplexing; each stage of Whiteman interferometer follows

Adjust the optical fiber length difference DL _i of the first and second paths to double the optical signal rate; Each level of Whiteman interferometer is connected in series with the next level of Whiteman interferometer; the length of the fiber is not required, and the multi-level Whiteman interferometer is connected in series. The n-level Whiteman interferometer can increase the optical signal rate to the original 2 ⁿ times the speed, n=1, 2, 3, 4.... 2. A kind of optical time division multiplexer according to claim 1, characterized in that: the self-focusing lens with pigtails is coated with a splitting film with a splitting ratio of 1:1, and the splitting film splits light in a broadband and flat wavelength range greater than 100 nm. 3. An optical time division multiplexer according to claim 1 or 2, characterized in that: the end face of the optical fiber is fired into the shape of a lens to change the light into parallel light.

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