CN1971394A - Transfer device of all-optical wavelength based on lithium niobate fiber waveguide ring antrum - Google Patents

Abstract

The invention discloses an all-optical wavelength conversion device based on a lithium niobate optical waveguide ring cavity, which comprises a first optical coupler, an erbium-doped optical fiber amplifier, a polarization controller, a PPLN optical waveguide, and an optical An isolator, a second optical coupler and a pump light wavelength selector constitute a ring cavity laser with a built-in PPLN optical waveguide. The PPLN optical waveguide processes the signal light and the pump light generated by the internal lasing of the ring cavity laser to cause nonlinear effects to achieve wavelength conversion; the converted idle light is output from the second optical coupler. On the one hand, the present invention makes full use of two kinds of cascaded second-order nonlinear effects in the PPLN optical waveguide to realize multiple all-optical wavelength conversion functions, which greatly improves the flexibility of wavelength conversion; on the other hand, the ring cavity laser inside the device is used to generate pumping Light, get rid of the previous dependence on expensive external cavity lasers as external pump light sources, the device structure is simple and easy to implement, the cost is greatly reduced, and the operation is reliable.

Description

All-optical wavelength conversion device based on lithium niobate optical waveguide ring cavity

technical field

The invention relates to the technical fields of nonlinear optical frequency mixing and all-optical signal processing, in particular to an all-optical wavelength conversion device based on a lithium niobate optical waveguide ring cavity.

Background technique

The all-optical wavelength converter can completely copy the information carried by one optical wavelength to another optical wavelength, and is an indispensable key device in the future Dense Wavelength Division Multiplexing (DWDM) optical network. Wavelength conversion technology helps to realize wavelength reuse, effectively perform dynamic routing selection, reduce network congestion and blocking rate, and then improve the flexibility and scalability of optical networks. Currently commonly used all-optical wavelength conversion technologies mainly include: cross-gain modulation (XGM), cross-phase modulation (XPM), nonlinear optical loop mirror (NOLM), laser gain saturation effect, four-wave mixing (FWM), second-order nonlinear linear effects and more. Among these schemes, the wavelength conversion technology based on the second-order nonlinear effect of the periodic polarization inversion lithium niobate (PPLN) passive optical waveguide has unique advantages, and its biggest features are fast response speed and strict wavelength conversion process. Transparency means that it has nothing to do with the bit rate and modulation format of the signal, so it has been highly valued by scientific and technological workers in various countries in recent years.

At present, many meaningful works have been carried out in the field of wavelength conversion based on the second-order nonlinear effect of PPLN optical waveguide at home and abroad, mainly including direct difference frequency (DFG), cascaded frequency multiplication and difference frequency (SHG+DFG) , a wavelength conversion technology based on second-order and cascaded second-order nonlinear effects such as cascaded sum frequency and difference frequency (SFG+DFG). In DFG wavelength conversion, since the pump light (0.77 μm) and the signal light (1.5 μm) are in different wavelength bands, it is difficult to simultaneously realize the single-mode transmission of the pump light and the signal light in the optical waveguide. The SHG+DFG wavelength conversion solves the difficulties encountered by the DFG wavelength converter. The injected pump light and signal light are both in the 1.5μm band, and can realize all-optical wavelength conversion in the 1.5μm band. Nevertheless, due to the very narrow wavelength response bandwidth (~0.3nm) of the pump light at the quasi-phase-matched (QPM) wavelength of the frequency-doubled (SHG) process in the SHG+DFG process, for a fixed input signal light, traditional The SHG+DFG type wavelength converter is difficult to realize the tunable output of converting idle light, and the tunable wavelength conversion is very important to enhance the flexibility of network management. SFG+DFG wavelength conversion can solve the problems encountered by DFG and traditional SHG+DFG wavelength converters at the same time. On the one hand, all incident light is in the 1.5μm band; on the other hand, even for signal light with fixed wavelength input, it can Conveniently implement tunable wavelength conversion. For example: In 2003, YHMin et al. wrote the article "Tunable all-optical wavelength conversion of 5ps pulses by cascaded sum-and difference frequency generation (cSFG/DFG) in a Ti: PPLN waveguide," in Proc. Optical Fiber Communications Conf, vol.2, Mar. ., 23-28 2003, pp.767-768, the first experimental report of tunable wavelength conversion based on SFG+DFG pulse signal light with a repetition rate of 10 GHz and a pulse width of 5 ps. However, in the reported SHG+DFG and SFG+DFG wavelength conversion schemes, it is necessary to use an expensive external cavity laser as an external pump light source, especially the wavelength conversion based on SFG+DFG requires the use of two external pump light sources at the same time , which greatly increases the complexity of the wavelength converter and increases the cost of the system. Although CQXu et al. in the article "Intracavity wavelength conversions employing a MgO-doped LiNbO ₃ quasi-phase-matched waveguide and an erbium-doped fiber amplifier," J.Opt.Soc.Amer.B, vol.20, No.10, In pp.2142-2149, Oct.2003, an intracavity wavelength conversion based on SHG+DFG was proposed to save an external pump light source, but since the pump light is located at the quasi-phase matching wavelength of the SHG process, tunable Intracavity wavelength conversion. In addition, the intracavity wavelength conversion based on SFG+DFG has not been reported so far because it needs to save two external pump light sources at the same time. In addition, most of the existing wavelength conversions are still single-channel-single-channel wavelength conversion, single-channel-dual-channel tunable wavelength conversion, single-channel-multi-channel ("broadcast") Conversion, and simultaneous conversion of multiple channels have received relatively little attention. In view of this, how to improve the traditional SHG+DFG wavelength conversion scheme to achieve tunable function, how to design a multifunctional wavelength converter (single-channel-single-channel, single-channel -dual-channel, single-channel-multi-channel tunable wavelength conversion and multi-channel simultaneous conversion) will have practical research and application value.

Contents of the invention

The object of the present invention is to provide an all-optical wavelength conversion device based on lithium niobate optical waveguide ring cavity, which has the characteristics of simple structure, low cost, reliable operation and good expandability.

An all-optical wavelength conversion device based on a lithium niobate optical waveguide ring cavity provided by the present invention is characterized in that the device includes a first optical coupler, an erbium-doped fiber amplifier, and a polarization controller sequentially connected by an optical path in a clockwise direction , a PPLN optical waveguide, an optical isolator, a second optical coupler and a pump light wavelength selector to form a first ring cavity laser;

The first optical coupler couples the incoming light wave, and after being amplified by the erbium-doped fiber amplifier, the polarization state of the light wave is adjusted by the polarization controller, and then enters the PPLN optical waveguide; The lasing is generated inside the ring cavity laser, and the pump light is sequentially transmitted in the clockwise direction in the ring cavity, and the wavelength of the pump light is determined by the pump light wavelength selector; The pump light generated by the laser is processed to cause nonlinear effect to realize wavelength conversion; the optical isolator is used to ensure the clockwise unidirectional transmission of the light wave in the ring cavity, and the converted idle light is output from the second optical coupler .

The invention aims at the shortcomings of the existing all-optical wavelength conversion technology, and provides an all-optical wavelength conversion device based on the PPLN optical waveguide ring cavity structure. On the one hand, the device makes full use of the two cascaded second-order nonlinear effects in the PPLN optical waveguide to realize a variety of all-optical wavelength conversion functions, which greatly improves the flexibility of wavelength conversion; on the other hand, it uses the ring cavity laser inside the device to generate pump Puguang has got rid of the previous dependence on expensive external cavity lasers as external pumping light sources. The device has a simple structure, is easy to implement, greatly reduces costs, and is reliable in operation. Specifically, compared with existing wavelength conversion technologies and devices, the present invention has the following advantages:

First, all-optical wavelength conversion based on the second-order nonlinear effect of PPLN has significant advantages compared with wavelength conversion based on semiconductor optical amplifier (SOA) cross-gain modulation and cross-phase modulation, and wavelength conversion based on fiber four-wave mixing .

(1) Compared with the semiconductor optical amplifier, the PPLN optical waveguide is a passive optical waveguide, so the PPLN optical waveguide itself will not introduce the influence of spontaneous emission noise during the wavelength conversion process;

(2) Compared with optical fiber four-wave mixing, PPLN has a higher nonlinear coefficient, which is conducive to the nonlinear effect, and the PPLN optical waveguide has a compact structure, easy integration and modularization, and reliable performance;

(3) There are rich second-order nonlinear effects such as frequency multiplication (SHG), sum frequency (SFG), and difference frequency (DFG) in PPLN optical waveguides, as well as cascaded second-order nonlinear effects between them, such as cascaded multiplier Frequency and difference frequency (SHG+DFG) and cascaded sum frequency and difference frequency (SFG+DFG), which greatly increase the selectivity of wavelength conversion based on the second-order nonlinear effect of PPLN optical waveguide;

(4) The wavelength conversion based on the second-order nonlinear effect of the PPLN optical waveguide also has the following characteristics of an ideal wavelength converter:

① Ultra-fast response speed (fs level);

②It has nothing to do with the bit rate and modulation format of the signal;

③Simultaneous conversion of multiple wavelengths and wide dynamic conversion range;

④ Spectrum and chirp inversion can be used for dispersion compensation;

⑤parameter amplification;

⑥ There is no internal frequency chirp during the conversion process.

Among them, the ultra-fast response speed and the characteristics independent of the signal bit rate and modulation format can enhance the high-speed signals with a rate of 40Gbit/s and above and various new modulation format signals (such as return-to-zero code RZ, carrier suppression return-to-zero code CSRZ, The processing ability of differential phase shift keying code DPSK, optical duobinary code ODB, etc.) makes wavelength conversion based on the second-order nonlinear effect of PPLN optical waveguide have potential advantages and application prospects in future high-speed all-optical signal processing technology.

Second, the cascaded frequency multiplication and difference frequency (SHG+DFG) second-order nonlinear effect based on the PPLN optical waveguide utilized by the present invention and the second-order nonlinear effect of the cascaded sum frequency and difference frequency (SFG+DFG) are used in the traditional SHG Improvements and enhancements have been made on the basis of +DFG and SFG+DFG.

(1) Inheriting the advantages of traditional SHG+DFG and SFG+DFG, the injected pump light and signal light are both in the 1.5μm band, which overcomes the second-order nonlinear effect of the traditional direct difference frequency (DFG) due to the pump light (0.77 μm) and signal light (1.5μm) are in different wavelength bands and it is difficult to perform single-mode transmission in the optical waveguide at the same time;

(2) The traditional SHG+DFG pump light is located at the quasi-phase-matching wavelength of the frequency doubling (SHG) process, and the response bandwidth is very narrow (~0.3nm). It is difficult to achieve tunable wavelength conversion for signal light of a given wavelength. The SHG+DFG used in the present invention improves this by placing the signal light at the quasi-phase-matching wavelength of the SHG process. For the fixed input signal light, the tunable output of converted idle light is realized by changing the wavelength of the pump light. In addition, by increasing the number of pump lights, the tunable wavelength conversion of single-channel to dual-channel and single-channel to multi-channel ("broadcast") of fixed input signal light is realized;

(3) Although the improved SHG+DFG achieves tunable wavelength conversion, the wavelength tunable range of the input signal light becomes very narrow (~0.3nm). This problem can be solved by using SFG+DFG. The tunable wavelength conversion of the variable input signal light can be easily realized by using two pump lights and adjusting their wavelengths appropriately, and both the input signal light and the output converted idle light can be tuned in a wide range (>75nm). The SFG+DFG utilized in the present invention further realizes tunable wavelength conversion of variable input signal light single-channel-multi-channel (“broadcasting”) by increasing the number of pump lights on this basis;

Third, the wavelength conversion device based on the PPLN ring cavity proposed by the present invention has a simple structure, is easy to implement, has low cost, and is stable and reliable.

(1) There is no need for an expensive external cavity laser to provide pump light. The pump light is generated by a ring cavity laser with a built-in PPLN optical waveguide. A single pump light can be easily generated by using different pump light wavelength selectors through flexible design , double-pumped light and multi-pumped light can realize a variety of wavelength conversion functions in various forms, which can greatly reduce the complexity and operating cost of the device. For example, for single-channel-multi-channel ("broadcast") wavelength conversion, multiple external cavity lasers can be saved by using a multi-wavelength selector, which has potential application in future dense wavelength division multiplexing optical networks value.

(2). The built-in PPLN optical waveguide and polarization controller in the ring cavity laser can increase the polarization inhomogeneity of the ring cavity, thereby alleviating the uniform broadening characteristics of the erbium-doped fiber amplifier. In addition, it is used in the wavelength selector of the ring cavity The tunable optical attenuator can also balance the gain competition of the erbium-doped fiber amplifier, which is very beneficial for the ring cavity laser to generate stable lasing light and thus ensure the stability of the wavelength conversion process.

Its four, the device of the present invention has good expandability.

(1) By replacing the pump light wavelength selector in the ring cavity laser, various tunable wavelengths such as fixed or variable input signal light, single-channel-three-channel, single-channel-four-channel, etc. can be further realized conversion;

(2) The wavelength selection device in the ring cavity laser can be changed flexibly. For example, for multi-wavelength selectors, the comb filter can also use Mach-Zehnder delay interferometer (MZ-DI), polarization-maintaining fiber loop mirror ( PMF-LM) and other devices with comb filter function.

Description of drawings

1 is a schematic diagram of the principle of an all-optical wavelength conversion device of the present invention;

Fig. 2 is the first structural schematic diagram of the all-optical wavelength conversion device of the present invention;

Figure 3(a)(b) are two kinds of single wavelength selective devices;

Figure 4(a)(b) are two kinds of dual wavelength selective devices;

Figure 5 is a multi-wavelength selective device;

Fig. 6 is a second structural schematic diagram of the all-optical wavelength conversion device of the present invention;

7 is a schematic diagram of the third structure of the all-optical wavelength conversion device of the present invention;

Figure 8 is a schematic diagram of the principle of optical fixed tunable wavelength conversion based on cascaded frequency multiplication and difference frequency (SHG+DFG): (a) single-channel-single-channel tunable wavelength conversion, (b) single-channel-dual-channel tunable Wavelength conversion, (c) single-channel to multi-channel ("broadcast") tunable wavelength conversion.

Figure 9 is a schematic diagram of the principle of optically variable and tunable wavelength conversion based on cascaded sum frequency and difference frequency (SFG+DFG) signals;

Figure 10 is a schematic diagram of the principle of optically variable single-channel-multi-channel ("broadcast") tunable wavelength conversion based on cascaded sum frequency and difference frequency (SHG+DFG) signals;

Fig. 11 is a schematic diagram of the principle of simultaneous conversion of multiple channels based on cascaded frequency multiplication and difference frequency (SHG+DFG).

Detailed ways

Below in conjunction with accompanying drawing and example the present invention is described in further detail.

The invention provides an all-optical wavelength conversion device based on a PPLN ring cavity structure without external injection of pump light, which is characterized in that a PPLN optical waveguide is built in a ring cavity laser, and PPLN cascaded frequency multiplication and difference frequency (SHG+DFG) are used And two cascaded second-order nonlinear effects of cascaded sum frequency and difference frequency (SFG+DFG) realize various all-optical wavelength conversion functions. The main body of the converter is a wavelength converter based on a PPLN ring cavity. As shown in Figure 1, it mainly includes a PPLN optical waveguide 1, a wavelength selector 2 and an erbium-doped fiber amplifier 3, which are sequentially connected to form a ring cavity laser with a built-in PPLN optical waveguide. The direction of the light path inside the annular cavity is clockwise. The pump light is generated by the internal lasing of the ring cavity laser, and the signal light and the pump light undergo a cascaded second-order nonlinear effect in the PPLN optical waveguide to generate converted output idle light, thereby realizing the wavelength conversion from signal light to converted idle light. All-optical wavelength conversion with multiple functions can be realized by selecting different wavelength conversion mechanisms and changing the specific internal composition of ring cavity lasers.

As shown in Figure 2, the device of the present invention includes a first optical coupler 4, an erbium-doped fiber amplifier 3, a polarization controller 5, a PPLN optical waveguide 1, an optical isolator 6, and a second optical coupler that are sequentially connected in a clockwise direction. The device 7 and the pump light wavelength selector 2 constitute the first ring cavity laser with built-in PPLN optical waveguide. Wherein, the first optical coupler 4 and the second optical coupler 7 respectively provide a signal light input port and a converted idle light output port to the outside.

The input signal light enters the device through the first optical coupler 4 , is amplified by the erbium-doped fiber amplifier 3 , and its polarization state is adjusted by the polarization controller 5 , and then enters the PPLN optical waveguide 1 . The pump light is generated by the internal lasing of the first ring cavity laser with a built-in PPLN optical waveguide, and the pump light travels clockwise in the ring cavity and passes through "erbium-doped fiber amplifier 3-polarization controller 5-PPLN optical waveguide 1- Optical isolator 6-the second optical coupler 7-pump light wavelength selector 2-the first optical coupler 4-erbium-doped fiber amplifier 3 ", wherein the erbium-doped fiber amplifier 3 provides the required gain for pumping light lasing , the polarization controller light 5 adjusts the polarization state of the pump light, the optical isolator 6 ensures that the light wave in the ring cavity is unidirectionally transmitted along the clockwise direction, and the pump light wavelength selector 2 is used to determine the internal excitation generated by the first ring cavity laser The wavelength of the pump light can be a single wavelength selector 2A, a dual wavelength selector 2B or a multi-wavelength selector 2C. The input signal light and the pump light generated by the internal lasing of the first ring cavity laser enter the PPLN optical waveguide 1 and undergo nonlinear effects therein to realize wavelength conversion, and the converted idle light is output from the second optical coupler 7 .

Based on the inventive device shown in Figure 2, the input signal light can be fixed, and there is no need to inject external pump light into single-channel-single-channel, single-channel-dual-channel and single-channel-multi-channel ("broadcast") tunable all-optical wavelength conversion. It is characterized in that the second-order nonlinear effect of cascaded frequency multiplication and difference frequency (SHG+DFG) occurs between the signal light and the pump light in the PPLN optical waveguide 1: the wavelength of the signal light is located in the quasi-phase of the PPLN optical waveguide frequency doubling (SHG) process At the matching wavelength, the frequency doubled light generated by the signal light through the frequency doubling (SHG) process interacts with the pump light generated by the internal lasing of the first ring cavity laser at the same time (DFG) and generates converted idle light. By adjusting the pump The wavelength of the pump light can be changed to convert the wavelength of idle light to achieve tunable output. The input signal light is fixed and is a single channel, and the channel number of the output converted idle light is determined by the number of pump lights. According to the pump light wavelength selector 2 in the ring cavity, the single wavelength selector 2A, the double wavelength selector 2B, Also the multi-wavelength selector 2C can correspondingly obtain single-channel-single-channel, single-channel-dual-channel, and single-channel-multiple-channel ("broadcast") tunable wavelength conversions.

Based on the inventive device shown in Figure 2, when the pump light wavelength selector 2 uses a dual wavelength selector 2B, it can also realize tunable all-optical wavelength conversion with variable input signal light and no need to inject external pump light . It is characterized in that in the PPLN optical waveguide 1, the second-order nonlinear effect of the cascaded sum frequency and difference frequency (SHG+DFG) occurs between the signal light and the two pump lights: the first pump generated by the signal light and the first ring cavity laser The pump light generates sum frequency light through the sum frequency (SFG) process. At the same time, the second pump light generated by the first ring cavity laser interacts with the sum frequency light by difference frequency (DFG) and generates converted idle light. With variable input signal light, the tunable output of converted idle light can be realized by appropriately changing the wavelengths of the two pumping lights.

As shown in FIG. 3( a ), the single wavelength selector 2A is composed of a first tunable optical attenuator 8 and a first tunable filter 9 . Light waves travel from right to left in this single wavelength selector. The first tunable filter 9 is used to select the required wavelength, and the first adjustable optical attenuator 8 is used to properly adjust the selected wavelength corresponding to the loss of the lasing light in the ring cavity to control the optical power of the lasing light. The positions of the first tunable optical attenuator 8 and the first tunable filter 9 can be interchanged.

The single wavelength selector 2A can also adopt the structure shown in FIG. 3( b ), which consists of an optical circulator 10 , an adjustable optical attenuator 8 and a fiber Bragg grating (FBG) 11 . The optical path direction of the light wave when it is transmitted from right to left in the single wavelength selector is "optical circulator 10 port a-optical circulator 10 port b-first adjustable optical attenuator 8-first fiber Bragg grating 11- First adjustable optical attenuator 8-optical circulator 10 port b-optical circulator 10 port c". Utilize the reflection spectrum of the first fiber Bragg grating 11 to select the desired wavelength, different fiber Bragg gratings can be selected to obtain different lasing wavelengths, and the first adjustable optical attenuator 8 is used to properly adjust the selected wavelength corresponding to the lasing light in the ring cavity loss to control the optical power of the lasing light.

As shown in Figure 4 (a), the dual wavelength selector 2B consists of first and second adjustable optical attenuators 8, 12, first and second tunable filters 9 and 13, and third and fourth optical couplers 14, 15 composition. When the light wave is transmitted from right to left in the dual wavelength selector, it first passes through the third optical coupler 14 and is divided into upper and lower paths for parallel transmission. The upper path passes through the first adjustable optical attenuator 8 and the first tunable filter 9, and the lower path The light waves of the upper and lower paths pass through the second adjustable optical attenuator 12 and the second tunable filter 13 successively, and the upper and lower paths of light waves are then coupled out through the fourth optical coupler 15 . The first and second tunable filters 9 and 13 are respectively used to determine the wavelengths of the two lasing lights in the ring cavity laser, and the first tunable optical attenuator 8 is used to properly adjust and control the wavelengths determined by the first tunable filter 9. The optical power of the laser light, the second adjustable optical attenuator 12 is used to properly adjust and control the optical power of the laser light determined by the second tunable filter 13 . The positions of the first tunable optical attenuator 8 and the first tunable filter 9 can be interchanged, and the positions of the second tunable optical attenuator 12 and the second tunable filter 13 can be interchanged.

Dual wavelength selector 2B also can adopt the structure shown in Figure 4 (b), by optical circulator 10, the first, the second adjustable optical attenuator 8,12 and the first, the second fiber Bragg grating 11,16 composition. There are two paths for light waves to travel from right to left in the dual wavelength selector. The first path is "optical circulator 10 port a-optical circulator 10 port b-first adjustable optical attenuator 8-first fiber Bragg grating 11-first adjustable optical attenuator 8-optical circulator 10 port b - Optical circulator 10 port c", wherein the reflection spectrum of the first fiber Bragg grating 11 determines the wavelength of the first lasing light, the wavelength of the first lasing light can be changed by selecting different first fiber Bragg gratings 11, the first can Dimmable attenuator 8 is used to adjust and control the optical power of the first lasing light; the second path is "optical circulator 10 port a-optical circulator 10 port b-first adjustable optical attenuator 8-first optical fiber Bragg grating 11-second tunable optical attenuator 12-second fiber Bragg grating 16-second tunable optical attenuator 12-first fiber Bragg grating 11-first tunable optical attenuator 8-optical circulator 10 port b-optical circulator 10 port c", wherein the reflection spectrum of the second fiber Bragg grating 16 determines the wavelength of the second lasing light, the wavelength of the second lasing light can be changed by selecting different second fiber Bragg gratings 16, the first , The second adjustable optical attenuators 8, 12 are used to adjust and control the optical power of the second laser light.

It is worth noting that the first and second adjustable optical attenuators 8 and 12 in Figure 4(a)(b) can increase the inhomogeneity of the two-path lasing light wave loss in the ring cavity, thereby weakening the The uniform broadening characteristics of the amplifier, and the use of polarization controllers in the ring cavity and polarization devices such as PPLN optical waveguides will also introduce inhomogeneity, which can ensure stable dual-wavelength lasing, so it is important to enhance the stability of the wavelength conversion process Sex is very rewarding.

As shown in FIG. 5 , the multi-wavelength selector 2C is composed of an erbium-doped fiber amplifier 17 , a bandpass filter 18 and a Fabry-Perot (FP) etalon 19 . Light waves travel from right to left in the multiple wavelength selector. The Fabry-Perot (FP) etalon 19 is equivalent to a comb filter, which constitutes the main body of the multi-wavelength selector after being connected with the bandpass filter 18 . The wavelength spacing of the multi-wavelength lasing is determined by the Fabry-Perot (FP) etalon 19 , and the number of lasing wavelengths depends on the bandwidth of the bandpass filter 18 . The positions of the bandpass filter 18 and the Fabry-Perot (FP) etalon 19 can be interchanged. Erbium-doped fiber amplifier 17 provides gain for multi-wavelength lasing inside the ring cavity.

As shown in Figure 6, when it is necessary to realize the variable input signal light without injecting external pump light single-channel-multi-channel ("broadcast") tunable wavelength conversion, the device of the present invention adds multiple wavelengths on the basis of Figure 2 The selector 20 can form a double-ring cavity laser with a built-in PPLN optical waveguide. The added second ring cavity laser consists of first optical coupler 4, erbium-doped fiber amplifier 3, polarization controller 5, PPLN optical waveguide 1, optical isolator 6, second optical coupler 7 and multi-wavelength selection along the counterclockwise direction The multi-wavelength selector 20 is formed by sequentially connecting optical paths, and the multi-wavelength selector 20 is used to generate multiple pumping lights, and its structure is the same as that of the multi-wavelength selector 2C. The structure of the first ring cavity laser is the same as that in FIG. 2 , and the direction of the optical path is clockwise, but the pump light wavelength selector 2 is a single wavelength selector 2A.

The input signal light enters the device through the first optical coupler 4 . The two ring cavity lasers emit one and multiple pump lights respectively, the erbium-doped fiber amplifier 3 provides gain, and the optical isolator 6 ensures the unidirectional transmission of the optical paths in the two ring cavity lasers. The signal light and the pump light generated by the internal lasing of the two ring cavity lasers are amplified by the erbium-doped fiber amplifier 3 and adjusted by the polarization controller 5, and then enter the PPLN optical waveguide 1, where nonlinear effects occur to realize wavelength conversion, and the conversion is obtained The converted idle light is output from the second optical coupler 7 .

Based on the inventive device shown in Fig. 6, it is possible to realize single-channel-multi-channel ("broadcast") tunable all-optical wavelength conversion with variable input signal light and no need to inject external pump light. It is characterized in that the signal light and the pump light in the PPLN optical waveguide 1 have a second-order nonlinear effect of the cascaded sum frequency and difference frequency (SFG+DFG): the signal light and the single pump light generated by the first ring cavity laser pass through and The sum frequency (SFG) process generates the sum frequency light. At the same time, the multi-channel pump light generated by the added second ring cavity laser interacts with the sum frequency light by difference frequency (DFG) to generate multiplexed idle light. By changing the input single-channel signal light, the tunable output of multi-channel conversion idle light can be realized by appropriately changing the wavelength of the laser pump light of the first and second ring cavity lasers, that is, single-channel-multi-channel with variable input signal light ("broadcast") tunable wavelength conversion.

As shown in Figure 7, when it is necessary to realize the all-optical wavelength conversion of multi-channel simultaneous conversion without injecting external pump light, the device of the present invention is the same as that of Figure 6, and also adds a multi-wavelength selector 20 on the basis of Figure 2 to form a built-in Double ring cavity laser with PPLN optical waveguide. Unlike FIG. 6 , there is no external input signal light in FIG. 7 . The multiple laser beams generated by the multi-wavelength selector 20 in FIG. 6 are multiple pump beams, and the multiple laser beams generated by the multi-wavelength selector 20 in FIG. 7 are regarded as multiple signal beams. The inventive device based on Fig. 7 can realize multi-channel simultaneous conversion without injecting external pump light, which is characterized in that in the PPLN optical waveguide 1, the cascaded frequency multiplication and difference frequency (SHG+DFG) of the pump light and the multi-channel signal light are two First-order nonlinear effect: the single pump light generated by the first ring cavity laser is located at the quasi-phase matching wavelength of the PPLN optical waveguide frequency doubling (SHG) process, and the frequency doubled light generated by the pump light through the frequency doubling (SHG) process is simultaneously with the The multi-channel signal light generated by the second ring cavity laser undergoes difference frequency (DFG) interaction and generates multiplexed idle light, which is output by the second optical coupler 7 . The signal light is multi-channel, and the converted idle light is also multi-channel and the number is equal to the signal light, that is, the simultaneous conversion of multiple channels is realized.

The working principle of the device of the present invention will be further described in detail below.

1. Single-channel-single-channel, single-channel-dual-channel and single-channel-multichannel ("broadcast") tunable wavelength conversion based on PPLN ring cavity signal optical fixation

1. Principle of wavelength conversion

1.1, single channel - single channel

As shown in Figure 8(a), based on the second-order nonlinear effect of cascaded frequency multiplication and difference frequency (SHG+DFG): the signal light 21 is located at the quasi-phase matching wavelength of the PPLN optical waveguide frequency doubling (SHG) process, and the signal light 21 undergoes a frequency doubling (SHG) process to generate frequency doubled light 22 , and at the same time, the pump light 23 interacts with the frequency doubled light 22 in a difference frequency (DFG) to obtain converted idle light 24 . According to the principle of energy conservation, the wavelengths of signal light 21, frequency doubled light 22, pump light 23 and converted idle light 24 satisfy the following relationship:

SHG: 1/λ _SH = 2/λ _S

DFG: 1/λ _i =1/λ _SH -1/λ _P (1)

SHG+DFG: 1/λ _i =2/λ _S -1/λ _P

1.2, single channel - dual channel

As shown in Figure 8(b), the basic principle is the same as single-channel-single-channel wavelength conversion, that is, based on SHG+DFG: the signal light 21 is located at the quasi-phase matching wavelength of the PPLN optical waveguide frequency doubling (SHG) process, and the signal light 21 The doubled frequency light 22 generated through the frequency doubling (SHG) process interacts with the two pumping lights 23 and 25 at the same time in a difference frequency (DFG) interaction, thereby generating two converted idle lights 24 and 26 . There is only one path of input signal light, and there are two paths of idle light for output conversion, so it corresponds to single-channel-dual-channel wavelength conversion. According to the principle of energy conservation, the wavelengths of the signal light 21, the frequency doubled light 22, the two pump lights 23, 25 and the two converted idle lights 24, 26 satisfy the following relationship:

SHG: 1/λ _SH = 2/λ _S

DFG: 1/λ _i1 = 1/λ _SH -1/λ _P1

SHG+DFG: 1/λ _i1 = 2/λ _S -1/λ _P1 (2)

DFG: 1/λ _i2 = 1/λ _SH -1/λ _P2

SHG+DFG: 1/λ _i2 = 2/λ _S -1/λ _P2

1.3, single channel - multi-channel ("broadcast")

As shown in Figure 8(c), the basic principle is the same as single-channel-single-channel and single-channel-dual-channel wavelength conversion, that is, based on SHG+DFG: the signal light 21 is located in the quasi-phase matching of the PPLN optical waveguide frequency doubling (SHG) process At the wavelength, the signal light 21 generates frequency doubled light 22 through a frequency doubling (SHG) process, and at the same time, the multiplexed pump light 27 interacts with the frequency doubled light 22 in difference frequency (DFG), thereby generating multiplexed idle light 28 . There is only one channel of input signal light, and the output converted idle light becomes multiple channels, that is, single-channel-multi-channel ("broadcast") wavelength conversion is realized. According to the principle of energy conservation, the wavelengths of signal light 21, frequency-doubled light 22, multi-channel pump light 27 and multiplexed idle light 28 satisfy the following relationship:

SHG: 1/λ _SH = 2/λ _S

DFG: 1/λ _i1 = 1/λ _SH -1/λ _P1

SHG+DFG: 1/λ _i1 = 2/λ _S -1/λ _P1

…… (3)

...

...

DFG: 1/λ _in = 1/λ _SH -1/λ _Pn

SHG+DFG: 1/λ _in ＝2/λ _S -1/λ _Pn

2. Wavelength conversion tunable principle

According to the inherent characteristics of the SHG+DFG process in the PPLN optical waveguide, the tunable range of the light wave at the quasi-phase matching wavelength of the frequency doubling (SHG) process is very narrow, and the traditional wavelength conversion scheme based on SHG+DFG pump light is located at the quasi-phase At the matching wavelength, although the wavelength of the input signal light can be changed in a wide range, it is difficult to achieve tunable wavelength conversion for a fixed input signal light. In the present invention, the signal light is placed at the quasi-phase matching wavelength. According to the formula (1), for a given signal light wavelength, the single-channel-single-channel tunable wavelength conversion can be easily realized by changing the pump light wavelength; according to Equation (2), for the input signal light with a fixed wavelength, the single-channel-dual-channel tunable wavelength conversion can be easily realized by adjusting the wavelength of the two pump lights; according to the formula (3), for a given signal light wavelength, The single-channel-multi-channel tunable wavelength conversion can be easily realized by changing the wavelength of multiple pumping lights.

2. Tunable wavelength conversion based on PPLN ring cavity signal light variable

1. Principle of wavelength conversion

As shown in FIG. 9 , based on the second-order nonlinear effect of the cascaded sum frequency and difference frequency (SFG+DFG): two pump lights 23 and 25 are required to participate. For the variable input signal light 21, the wavelength of the first pump light 23 is adjusted so that it meets or approximately satisfies the quasi-phase matching condition of the sum-frequency (SFG) process with the wavelength of the signal light 21. At this time, the first pump light 23 The wavelength of the sum signal light 21 is approximately symmetrical to the quasi-phase matching wavelength of the frequency doubling (SHG) process, the signal light 21 and the first pump light 23 generate the sum frequency light 29 through the sum frequency (SFG) process, and at the same time, the second A difference frequency (DFG) interaction occurs between the pump light 25 and the sum frequency light 29 to obtain converted idle light 30 . According to the principle of energy conservation, the wavelengths of the signal light 21, the first pump light 23, the sum-frequency light 29, the second pump light 25 and the converted idle light 30 satisfy the following relationship:

SFG: 1/λ _SF ＝1/λ _S +1/λ _P1

DFG: 1/λ _i = 1/λ _SF -1/λ _P2 (4)

SFG+DFG: 1/λ _i ＝1/λ _S +1/λ _P1 -1/λ _P2

2. Wavelength conversion tunable principle

For the tunable wavelength conversion based on the fixed SHG+DFG signal light, since the signal light is located at the quasi-phase matching wavelength of the frequency doubling (SHG) process, the variable range of the signal light wavelength is very small (3dB bandwidth ~ 0.3nm). In contrast, for the wavelength conversion based on SFG+DFG, when the wavelength of the signal light 21 changes, as long as the wavelength of the first pump light 23 is properly adjusted to keep the wavelength of the sum frequency light 29 unchanged, so as to satisfy or approximate Satisfying the quasi-phase matching condition of the sum-frequency (SFG) process, the wavelength of the signal light 21 can vary within a very wide (3dB bandwidth>75nm) wavelength range. According to formula (4), when the wavelength of the sum-frequency light 29 remains unchanged, the wavelength of the first pump light 23 is determined by the wavelength of the input signal light 21, and the wavelength of the converted idle light 30 is determined by the wavelength of the second pump light 25 . By properly adjusting the wavelengths of the two pump lights 23, 25, the tunable wavelength conversion from variable input signal light to variable output converted idle light can be realized very conveniently.

3. Single-channel-multi-channel ("broadcast") tunable wavelength conversion based on optically variable PPLN ring cavity signal

1. Principle of wavelength conversion

As shown in Figure 10, the basic principle is the same as the tunable wavelength conversion with variable signal light, that is, based on the second-order nonlinear effect of the cascaded sum frequency and difference frequency (SFG+DFG): single-channel-n-channel wavelength conversion requires n +1 for the involvement of Pump Light 23, 31. For the variable input signal light 21, the wavelength of the first pump light 23 is adjusted so that it meets or approximately satisfies the quasi-phase matching condition of the sum-frequency (SFG) process with the wavelength of the signal light 21. At this time, the first pump light 23 The wavelength of the sum signal light 21 is approximately symmetrical with respect to the quasi-phase matching wavelength of the frequency doubling (SHG) process, and the sum frequency light 29 generated by the signal light 21 and the first pump light 23 through the sum frequency (SFG) process is simultaneously with the other n road pumps Difference frequency (DFG) interaction occurs between the Pu light 31 and n-way converted idle light 32 is obtained. According to the principle of energy conservation, the wavelengths of the signal light 21, the first pump light 23, the sum frequency light 29, the other n pump light 31 and the n converted idle light 32 satisfy the following relationship:

SFG: 1/λ _SF ＝1/λ _S +1/λ _P0

DFG: 1/λ _i1 = 1/λ _SF -1/λ _P1

SFG+DFG: 1/λ _i1 ＝1/λ _S +1/λ _P0 -1/λ _P1

…… (5)

...

...

DFG: 1/λ _in = 1/λ _SF -1/λ _Pn

SFG+DFG: 1/λ _in ＝1/λ _S +1/λ _P0 -1/λ _Pn

2. Wavelength conversion tunable principle

Similar to the variable tunable wavelength conversion based on SFG+DFG signal light, according to formula (5), for a given signal light wavelength, when the wavelength of the sum-frequency light 29 is kept constant, the wavelength of the first pump light 23 is given by The wavelength of the input signal light 21 is determined, and the wavelength of the n-way converted idle light 32 is correspondingly determined by the wavelength of the n-way pump light 31 . By properly adjusting the wavelengths of the first pumping light 23 and the other n pumping lights 31 , it is easy to realize single-channel-multi-channel ("broadcast") tunable wavelength conversion with variable signal light.

4. Simultaneous conversion of multiple channels based on PPLN ring cavity

1. Principle of wavelength conversion

As shown in Figure 11, based on the second-order nonlinear effect of cascaded frequency multiplication and difference frequency (SHG+DFG): the pump light 23 is located at the quasi-phase matching wavelength of the frequency multiplication (SHG) process, and the pump light 23 has undergone frequency multiplication (SHG) process generates frequency-doubled light 33, and at the same time, n-way signal light 34 interacts with frequency-doubled light 33 to obtain corresponding n-way converted idle light 35, which realizes multi-channel simultaneous wavelength convert. According to the principle of energy conservation, the wavelengths of the pump light 23, the frequency doubled light 33, the n-channel signal light 34 and the n-channel converted idle light 35 satisfy the following relationship:

SHG: 1/λ _SH = 2/λ _P

DFG: 1/λ _i1 = 1/λ _SH -1/λ _S1

SHG+DFG: 1/λ _i1 = 2/λ _P -1/λ _S1

…… (6)

...

...

DFG: 1/λ _in = 1/λ _SH -1/λ _Sn

SHG+DFG: 1/λ _in ＝2/λ _P -1/λ _Sn

In a word, the device of the present invention can flexibly realize various all-optical wavelength conversion functions without injecting external pump light, especially the tunable all-optical wavelength conversion of single-channel-dual-channel and single-channel-multi-channel ("broadcast"), These are of great significance for promoting the development of all-optical wavelength conversion technology and new devices.

Claims (8)

1, a kind of full optical wavelength converting device based on lithium niobate fiber waveguide ring antrum, it is characterized in that: this device comprises along clockwise direction first photo-coupler (4), Erbium-Doped Fiber Amplifier (EDFA) (3), Polarization Controller (5), PPLN optical waveguide (1), optoisolator (6), second photo-coupler (7) and the pump light wavelength selector (2) of light path connection successively, constitutes first annular cavity laser;

Wherein first photo-coupler (4) is coupled to the light wave that enters, and by Polarization Controller (5) polarization state of light wave is adjusted after Erbium-Doped Fiber Amplifier (EDFA) (3) amplifies again, enters PPLN optical waveguide (1) then; Pump light is by the inner sharp generation of penetrating of first annular cavity laser of built-in PPLN optical waveguide, and pump light is transmission along clockwise direction in ring cavity, and the pump light wavelength is determined by pump light wavelength selector (2); PPLN optical waveguide (1) is used for flashlight and the inner sharp pump light of penetrating generation of first annular cavity laser are handled, and makes it that nonlinear effect take place and realizes wavelength Conversion; Optoisolator (6) is used to guarantee the interior light wave of ring cavity one-way transmission along clockwise direction, and the conversion idle light that is converted to is exported from second photo-coupler (7).

2, full optical wavelength converting device according to claim 1 is characterized in that: outer signals light is in first photo-coupler (4) injection device; Pump light wavelength selector (2) is made up of adjustable optical attenuator (8) and tunable optic filter (9).

3, full optical wavelength converting device according to claim 1 is characterized in that: outer signals light is in first photo-coupler (4) injection device; Pump light wavelength selector (2) comprises optical circulator (10), first adjustable optical attenuator (8) and first Fiber Bragg Grating FBG (11); The port b of optical circulator (10) links to each other with first adjustable optical attenuator (8), and first Fiber Bragg Grating FBG (11) links to each other with first adjustable optical attenuator (8), and port a, the c of optical circulator (10) links to each other with second, first photo-coupler (7,4) respectively.

4, full optical wavelength converting device according to claim 1 is characterized in that: outer signals light is in first photo-coupler (4) injection device; The structure of pump light wavelength selector (2) is: first tunable optic filter (9) links to each other with first adjustable optical attenuator (8) and forms branch road, second adjustable optical attenuator (12) links to each other with second tunable optic filter (13) and forms another branch road, link to each other with the 3rd, the 4th photo-coupler (14,15) respectively after the parallel connection of these two branch roads, the other end of the 3rd, the 4th photo-coupler (14,15) links to each other with second, first photo-coupler (7,4) respectively.

5, full optical wavelength converting device according to claim 1 is characterized in that: outer signals light is in first photo-coupler (4) injection device; The structure of pump light wavelength selector (2) is: first variable optical attenuator (8), first Fiber Bragg Grating FBG (11), second variable optical attenuator (12), second Fiber Bragg Grating FBG (16) back connected in series successively are connected by the port b of first variable optical attenuator (8) with optical circulator (10); Port a, the c of optical circulator (10) links to each other with second, first photo-coupler (7,4) respectively.

6, full optical wavelength converting device according to claim 1 is characterized in that: outer signals light is in first photo-coupler (4) injection device; Pump light wavelength selector (2) comprises Erbium-Doped Fiber Amplifier (EDFA) (17), bandpass filter (18) and Fabry-Perot etalon (19); The input end of Erbium-Doped Fiber Amplifier (EDFA) (17) links to each other with second photo-coupler (7) as the input end of pump light wavelength selector (2), the output terminal of Erbium-Doped Fiber Amplifier (EDFA) (17) links to each other with bandpass filter (18) or Fabry-Perot etalon (19), and the output terminal of pump light wavelength selector (2) links to each other with first photo-coupler (4).

7, full optical wavelength converting device according to claim 1, it is characterized in that: described pump light wavelength selector (2) is a single wavelength selector (2A), this device also comprises multi-wavelength selector switch (20), and multi-wavelength selector switch (20) comprises Erbium-Doped Fiber Amplifier (EDFA), bandpass filter and Fabry-Perot etalon; The input end of Erbium-Doped Fiber Amplifier (EDFA) is as the input end of multi-wavelength selector switch (20), and the output terminal of Erbium-Doped Fiber Amplifier (EDFA) links to each other with bandpass filter or Fabry-Perot etalon;

The input end of multi-wavelength selector switch (20) links to each other with the output terminal of second photo-coupler (7), and the output terminal of multi-wavelength selector switch (20) links to each other with the input end of first photo-coupler (4), constitutes second annular cavity laser of built-in PPLN optical waveguide;

The multiwavelength laser that second annular cavity laser of built-in PPLN optical waveguide produces is as multiple signals light.

8, according to claim 2 or 3 described full optical wavelength converting devices, it is characterized in that: outer signals light is in first photo-coupler (4) injection device; This device also comprises multi-wavelength selector switch (20), and multi-wavelength selector switch (20) comprises Erbium-Doped Fiber Amplifier (EDFA), bandpass filter and Fabry-Perot etalon; The input end of Erbium-Doped Fiber Amplifier (EDFA) is as the input end of multi-wavelength selector switch (20), and the output terminal of Erbium-Doped Fiber Amplifier (EDFA) links to each other with bandpass filter or Fabry-Perot etalon;

The input end of multi-wavelength selector switch (20) links to each other with the output terminal of second photo-coupler (7), and the output terminal of multi-wavelength selector switch (20) links to each other with the input end of first photo-coupler (4), constitutes second annular cavity laser of built-in PPLN optical waveguide.

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