CN1996136A - All-optical code type conversion device based on nonlinear optical waveguide loop mirror - Google Patents

Abstract

The invention discloses an all-optical code conversion device based on a nonlinear optical waveguide ring mirror. The device includes a nonlinear optical waveguide, a tunable delay line, a tunable filter and two optical couplers; the nonlinear optical waveguide is a PPLN or AlGaAs optical waveguide, and the nonlinear optical waveguide is connected with two optical couplers to form a built-in nonlinear optical waveguide. A circular mirror of a linear optical waveguide; one port of the second optical coupler is connected to the tunable delay line to provide a pumping light input port to the outside, and one port of the first optical coupler is used as the input port for the input non-return-to-zero code signal light, which is located at the same The other port on the side is connected to the tunable filter to provide an output port. The device of the invention utilizes the second-order nonlinear effect of the nonlinear optical waveguide sum frequency, the second-order nonlinear effect of the cascaded sum frequency and difference frequency, and the interference principle to realize all-optical code type conversion from non-return-to-zero codes to return-to-zero codes. The device is simple in structure, easy to implement, reliable in operation, good in expandability, fast in code pattern conversion process, and free from the influence of spontaneous radiation noise.

Description

All-optical code conversion device based on nonlinear optical waveguide loop mirror

technical field

The invention belongs to the field of nonlinear optical frequency mixing technology and the field of all-optical signal processing, and specifically relates to an all-optical code conversion device based on a nonlinear optical waveguide ring mirror. The device is based on periodic polarization inversion lithium niobate (PPLN ) or periodic domain inversion of aluminum gallium arsenide (AlGaAs) passive optical waveguide second-order and cascaded second-order nonlinear effects, using a fiber loop mirror structure to realize non-return-to-zero code to return-to-zero code tunable all-optical code conversion.

Background technique

The future all-optical network will combine two key technologies of wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM). It is more suitable to use the return-to-zero code (RZ) with the network. Therefore, at the interface between the two, the all-optical code conversion between the non-return-to-zero code and the return-to-zero code is particularly important, and has been paid attention to by researchers from various countries in recent years.

At present, a lot of very meaningful work has been carried out in all-optical code conversion from non-return-to-zero codes to return-to-zero codes. The reported schemes mainly use nonlinear optical loop mirrors and walk-off balanced nonlinear fiber optic loop mirrors. , vertical cavity surface emitting laser, traveling wave semiconductor laser amplifier, semiconductor optical amplifier, Mach-Zehnder interferometer and so on. For example: In 1995, L.Noel et al. in the article "Four WDM channel NRZ to RZ format conversion using a singlesemiconductor laser amplifier," in Electron.Lett., vol.31, no.4, 1995, pp.277-272, Using the cross-phase modulation effect of traveling-wave semiconductor laser amplifiers to report the all-optical code conversion of 4-channel non-return-to-zero codes to return-to-zero codes at a rate of 10Gbit/s; in 2003, L.Xu et al. format conversion between RZ and NRZ based on a Mach-Zehnder interferometric wavelength converter", in IEEE Photon.Technol.Lett., vol.15, no.2, 2003, pp.308-310, using cross-phase modulation based on semiconductor optical amplifiers The Mach-Zehnder interferometer structure experimentally reported the all-optical code conversion of 2.5Gbit/s non-return-to-zero code to return-to-zero code. These schemes are relatively mature in technology, and also show a good conversion effect. However, there are still some shortcomings, such as the response speed is not fast enough to work at a high speed of 40Gbit/s, and the inevitable spontaneous emission noise in the active medium will also have an adverse effect on high-speed all-optical code conversion, etc. These cannot adapt to the requirements of future high-speed optical communication networks. It can be seen that finding and exploring new all-optical code conversion technology and designing corresponding conversion devices will have important research and application value. In recent years, nonlinear passive optical waveguides such as periodic polarization inversion lithium niobate (PPLN) and periodic domain inversion aluminum gallium arsenide (AlGaAs) have been widely used in all-optical wavelength conversion, which have ultra-fast response speed , and is not affected by spontaneous emission noise, so it also has potential advantages in high-speed all-optical code conversion.

Contents of the invention

The object of the present invention is to provide a kind of all-optical pattern conversion device based on nonlinear optical waveguide loop mirror, this device has the characteristics of simple structure, easy to realize, reliable operation and good scalability, and realizes all-optical pattern transformation Good flexibility and fast response.

An all-optical code conversion device based on a nonlinear optical waveguide loop mirror provided by the present invention is characterized in that the device includes a nonlinear optical waveguide, a first optical coupler, a second optical coupler, and a tunable delay line and a first tunable filter; the nonlinear optical waveguide is a PPLN optical waveguide or an AlGaAs optical waveguide, and the nonlinear optical waveguide, the first optical coupler and the second optical coupler form a loop mirror with a built-in nonlinear optical waveguide;

One end of the nonlinear optical waveguide is connected to the first port of the second optical coupler, and the other end is connected to the first port of the first optical coupler; Two, the third port, the second port of the second optical coupler is connected with the adjustable delay line, and the input port of the pump light is provided externally, the third port of the second optical coupler is connected with the second port of the first optical coupler The first and second ports of the first optical coupler are located on the same side, and the third and fourth ports are also provided on the opposite side. The third port of the first optical coupler is used as the input non-return-to-zero code signal The light injection port, the fourth port is connected with the first tunable filter and provides an output port to the outside.

The device of the invention utilizes the second-order nonlinear effect of the sum frequency (SFG) in the PPLN or AlGaAs nonlinear optical waveguide, the second-order nonlinear effect of the cascaded sum frequency and difference frequency (SFG+DFG) and the interference principle to realize non-return-to-zero code to return Zero code all-optical code conversion. Compared with the existing non-return-to-zero code to return-to-zero code all-optical code type conversion technology and device, the present invention has the following advantages:

First, PPLN and AlGaAs optical waveguides respond quickly and are transparent to the bit rate of the signal, so it can realize high-speed all-optical code conversion at a rate of 40Gbit/s and above, which is difficult to achieve with traditional code conversion schemes;

Second, PPLN and AlGaAs optical waveguides are passive optical waveguides, so the code conversion process is not affected by spontaneous emission noise;

Third, the code conversion process based on PPLN and AlGaAs optical waveguide will not generate internal frequency chirp;

Fourth, the rich second-order nonlinear effects and cascaded second-order nonlinear effects in PPLN and AlGaAs optical waveguides can realize a variety of all-optical code conversion functions, such as single-channel-single-channel, single-channel-three-channel and single-channel - Multi-channel all-optical code conversion;

Fifth, all-optical code conversion based on PPLN or AlGaAs optical waveguide second-order and cascaded second-order nonlinear effects has good tunable performance;

Its six, the device of the present invention adopts the annular mirror structure based on PPLN or AlGaAs optical waveguide, and device structure is simple, is easy to realize, and the two-way light wave that transmits clockwise and anticlockwise in the annular mirror passes through the same path, so the device's Stable and reliable;

Seventh, the device of the present invention has good expandability. By changing the number of input continuous control lights, various all-optical code conversion functions such as single-channel-five-channel, single-channel-seven-channel, etc. can be easily realized.

Description of drawings

Fig. 1 is the schematic diagram of the principle of the all-optical pattern conversion device based on the sum-frequency second-order nonlinear effect of the present invention;

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

3 is a schematic diagram of the principle of tunable all-optical code conversion based on the sum-frequency secondary nonlinear effect of the present invention;

Fig. 4 is a schematic diagram of the principle of a single-channel-three-channel all-optical code conversion device based on the cascaded sum frequency and difference frequency second-order nonlinear effect of the present invention;

Fig. 5 is a second structural schematic diagram of the all-optical code conversion device of the present invention;

Fig. 6 is a schematic diagram of the principle of single-channel-three-channel tunable all-optical code conversion based on the second-order nonlinear effect of cascaded sum frequency and difference frequency in the present invention;

Fig. 7 is a schematic diagram of the principle of a single-channel-multi-channel all-optical code conversion device based on the cascaded sum frequency and difference frequency second-order nonlinear effect of the present invention;

Fig. 8 is a third structural schematic diagram of the all-optical code conversion device of the present invention;

Fig. 9 is a schematic diagram of the principle of single-channel-multi-channel tunable all-optical code conversion based on the second-order nonlinear effect of cascaded sum frequency and difference frequency in the present invention.

Detailed ways

The device of the present invention is based on the sum-frequency second-order nonlinear effect and the principle of interference, as shown in Figure 1, the working principle of the device of the present invention is:

(1) The input non-return-to-zero code signal light equal power is divided into two paths.

(2) Input the pumping light synchronized with the optical clock of the non-return-to-zero code signal, the pumping light is a periodic pulse sequence, and the pulse width is less than the bit period.

(3) The first signal light is bit-aligned with the pump light and injected into the PPLN or AlGaAs nonlinear optical waveguide in the same direction, and the sum-frequency second-order nonlinear effect occurs in it: a signal light photon and a pump light photon are annihilated and then A sum-frequency photon is produced. Therefore, the part of the signal light overlapping with the pump light in the time domain will be attenuated and introduce a nonlinear phase shift in the sum-frequency process. That is to say, at the output end of the nonlinear optical waveguide, the middle part of the signal light bit "1" corresponding to the position of the pump light will form a "pit" and introduce a nonlinear phase shift due to consumption. The shape of the "pit" is the same as that of the pump light. The shape of the Pu light pulse is similar, as shown in the dotted box A in Fig. 1 .

(4) The second signal light does not experience sum-frequency interaction, so there will be no phenomenon that the middle part of the first signal light bit "1" forms a "pit" and introduces a nonlinear phase shift. The time-domain waveform is similar to the time-domain waveform of the input NRZ signal light, as shown by the dashed box B in FIG. 1 . However, the second path of signal light introduces a π phase shift relative to the first path of signal light.

(5) The first signal light (the middle part of the bit "1" forms a "pit" and introduces a nonlinear phase shift) and the second signal light (introduces a π phase shift relative to the first signal light) recombine and occur Interference, the result of the interference is to obtain the signal light output of the return-to-zero code, so that the all-optical code conversion from the non-return-to-zero code to the return-to-zero code is realized, and the wavelength remains unchanged before and after the code conversion.

As shown in FIG. 2 , the device of the present invention includes a nonlinear optical waveguide 1 , a first optical coupler 2 , a second optical coupler 3 , a tunable delay line 4 and a first tunable filter 5 . The nonlinear optical waveguide 1 is a PPLN optical waveguide or an AlGaAs optical waveguide. One end of the nonlinear optical waveguide 1 is connected to the first port G of the second optical coupler 3 , and the other end is connected to the first port F of the first optical coupler 2 . The side opposite to the first port in the second optical coupler 3 is provided with second and third ports H and K, wherein the second port H is connected to the tunable delay line 4 and provides an input port for pumping light to the outside , the third port K is connected to the second port E of the first optical coupler 2 . The first and second ports F and E of the first optical coupler 2 are located on the same side, and the third and fourth ports C and D are also provided on the opposite side. The third port C of the first optical coupler 2 is used as an injection port for inputting the NRZ code signal light, and the fourth port D is connected with the first tunable filter 5 to provide an output port to the outside. The nonlinear optical waveguide 1, the first optical coupler 2 and the second optical coupler 3 constitute a loop mirror with a built-in nonlinear optical waveguide.

The input NRZ code signal light is injected into the device through the third port C of the first optical coupler 2, and is divided into two signals of equal power at the second and first ports E and F of the first optical coupler 2 Light travels in the ring mirror in clockwise and counterclockwise directions, respectively. The input pumping light is synchronized with the optical clock of the non-return-to-zero code signal, and the pumping light is a periodic pulse sequence with a pulse width less than the bit period. The pumping light enters the device through the second optical coupler 3 after passing through the tunable delay line 4, and transmits therein in a clockwise direction. The tunable delay line 4 is used to adjust the relative delay between the pump light and the first signal light transmitted clockwise, so as to ensure the bit alignment of the two. The first signal light at the second port E of the first optical coupler 2 is transmitted in the clockwise direction in the ring mirror, passes through the second optical coupler 3 and the nonlinear optical waveguide 1 in turn, and then reaches the port of the first optical coupler 2 The first port F; the second signal light at the first port F of the first optical coupler 2 is transmitted in the counterclockwise direction in the ring mirror, and then passes through the nonlinear optical waveguide 1 and the second optical coupler 3 in turn to reach the first The second port E of the optical coupler 2; then the two signal lights are recombined by the first optical coupler 2 and then output by interference at the fourth port D. Therefore, the first path of signal light transmitted in the clockwise direction passes through "first optical coupler 2 third port C-first optical coupler 2 second port E-second optical coupler 3-nonlinear optical waveguide 1- The first optical coupler 2 first port F-the first optical coupler 2 fourth port D", the second signal light transmitted in the counterclockwise direction passes through the "first optical coupler 2 third port C-first optical Coupler 2 first port F—nonlinear optical waveguide 1—second optical coupler 3—first optical coupler 2 second port E—first optical coupler 2 fourth port D″. It is worth noting that when passing through the first optical coupler 2 for the first time, the signal light of the second path passes from the third port C to the first port F relative to the signal light of the first path passing from the third port C to the second port E A π/2 phase shift will be introduced. When passing through the first optical coupler 2 for the second time, the second signal light passes from the second port E to the fourth port D relative to the first signal light from the first port F to the fourth port. Four-port D again introduces a π/2 phase shift. Therefore, when the two signal lights are output by interference at the fourth port D of the first optical coupler 2 , the second signal light transmitted in the counterclockwise direction introduces a total π phase shift relative to the first signal light transmitted in the clockwise direction. The first signal light transmitted in the clockwise direction is injected into the nonlinear optical waveguide 1 in the same direction as the pump light, and the sum-frequency second-order nonlinear effect occurs under the condition of satisfying the sum-frequency process quasi-phase matching (QPM), and the signal light bit " The position corresponding to the pump light in the middle part of 1" will form a "pit" and introduce a nonlinear phase shift due to consumption. The shape of the "pit" is similar to the shape of the pump light pulse. Therefore, the time-domain waveform of the first signal light transmitted in the clockwise direction when it reaches the fourth port D of the first optical coupler 2 is shown in the dotted box A in FIG. 1 . The second signal light transmitted in the counterclockwise direction is opposite to the pump light. When the first signal light in the clockwise direction and the pump light meet the sum frequency quasi-phase matching condition, the second signal light in the counterclockwise direction and the pump light The optical and frequency phase mismatch is serious, and the signal light and pump light transmitted in the reverse direction cannot effectively contact each other, so the second signal light and pump light transmitted in the counterclockwise direction occur in the nonlinear optical waveguide 1 And frequency effects can be ignored. When the second signal light transmitted in the counterclockwise direction reaches the fourth port D of the first optical coupler 2, the middle part of the bit "1" does not appear the "pit" phenomenon and introduces a nonlinear phase shift, as shown in the dotted line in Figure 1 Shown in Box B. The two-way signal light transmitted clockwise and counterclockwise is output by interference at the fourth port D of the first optical coupler 2 to obtain the signal light of the return-to-zero code, and then filtered by the first tunable filter 5 to output the return-to-zero code signal light .

Based on the inventive device shown in Figure 2, by appropriately changing the wavelengths of the signal light and the pump light, the all-optical code conversion from tunable non-return-to-zero codes to return-to-zero codes can be easily realized. The tunable principle is shown in FIG. 3 , the signal light 6 and the pump light 7 generate sum-frequency light 8 through sum-frequency interaction. For the variable input signal light 6, as long as the wavelength of the pump light 7 is properly adjusted to keep the wavelength of the sum-frequency light 8 constant, thereby satisfying or approximately satisfying the quasi-phase matching condition of the sum-frequency process, the signal light 6 can be used in a wide range It is tunable within the range. According to the principle of energy conservation, the wavelengths of signal light 6, pump light 7 and sum frequency light 8 satisfy the following relationship:

SFG: 1/λ _SF ＝1/λ _S +1/λ _P (1)

According to formula (1), when the wavelength of the sum-frequency light 8 is kept constant, the wavelengths of the signal light 6 and the pump light 7 are approximately symmetrically distributed with respect to the quasi-phase matching wavelength in the nonlinear optical waveguide frequency doubling process, and the wavelength of the pump light 7 is It is determined by the wavelength of the signal light 6 . Based on the sum-frequency effect, by properly adjusting the wavelength of the pump light 7 , the code conversion from the variable input non-return-to-zero code signal light to the return-to-zero code signal light can be realized.

When realizing single-channel-three-channel non-return-to-zero code to return-to-zero code all-optical code pattern conversion, the device of the present invention is based on the second-order nonlinear effect of cascaded sum frequency and difference frequency and the principle of interference. As shown in Figure 4, a continuous control light is added on the basis of Figure 1, and the input non-return-to-zero code signal light and the equal power of the continuous control light are divided into two paths. The first signal light, the first control light and the pump light are injected into the PPLN or AlGaAs nonlinear optical waveguide in the same direction, and the second-order nonlinear effect of the cascaded sum frequency and difference frequency occurs in it: in the sum frequency process, A signal light photon and a pump light photon are annihilated to produce a sum frequency photon; meanwhile, in the difference frequency process, a sum frequency photon is annihilated to produce a control light photon and a converted idle light photon. Therefore, while generating the sum-frequency light and converting the idle light, the part of the signal light overlapping with the pump light in the time domain will be attenuated and introduce a nonlinear phase shift during the sum-frequency process, while the control light at these positions will be amplified and introduce a nonlinear phase shift. That is to say, as shown in the dotted box A in Fig. 4, at the output end of the nonlinear optical waveguide, except for the position corresponding to the pump light in the middle part of the signal light bit "1", a "pit" will be formed due to consumption and a nonlinear phase will be introduced. In addition, the control light at these positions will form "protrusions" due to being amplified and introduce a nonlinear phase shift. The shapes of "pits" and "protrusions" are similar to the shape of the pump light pulse. In addition, it is worth noting that the converted idle light generated during the cascaded sum frequency and difference frequency process is a return-to-zero code. The second signal light and the second control light do not experience the interaction of the cascaded sum frequency and difference frequency, and there will be no "pit" in the middle part of the first signal light bit "1" and the formation of the first control light "" "protrusion" and introduce the phenomenon of nonlinear phase shift, as shown in the dotted box B in Fig. 4. However, the second path of signal light introduces a π phase shift relative to the first path of signal light, and the second path of control light also introduces a π phase shift relative to the first path of control light. The result of the interference after the recombination of the two signal lights is to obtain the signal light output of the return-to-zero code. The result of the interference after the recombination of the two control lights is to obtain the control light output of the return-to-zero code, plus the return-to-zero code to convert the idle light, In this way, the all-optical code conversion from single-channel to three-channel non-return-to-zero code to return-to-zero code is realized. The wavelength of one channel remains unchanged before and after code conversion, while the wavelength of the other two channels changes before and after code conversion. That is, code conversion and wavelength conversion are realized at the same time.

As shown in FIG. 5 , the device of the present invention adds a third optical coupler 9 , a fourth optical coupler 10 , a second tunable filter 11 and a third tunable filter 12 on the basis of FIG. 2 . Wherein, one end of the third optical coupler 9 is connected to the third port C of the first optical coupler, and the two ports on the other side provide the input port of the non-return-to-zero code signal light and the continuous control light to the outside respectively; the fourth optical coupler One end of the optical coupler 10 is connected to the fourth port D of the first optical coupler, and the three ports on the other side are respectively connected to the first tunable filter 5, the second tunable filter 11, and the third tunable filter 12. Three output ports are provided externally, which respectively output return-to-zero code signal light, return-to-zero code idle light and return-to-zero code control light.

The input non-return-to-zero code signal light and the continuous control light are coupled through the third optical coupler 9 and then injected into the ring mirror with built-in nonlinear optical waveguide through the third port C of the first optical coupler 2, and the first optical coupler The second and first ports E and F of 2 are divided into two channels of equal power signal light and two channels of control light, which are respectively transmitted in the ring mirror along the clockwise direction and the counterclockwise direction. The input pump light passes through the tunable delay line 4 and then enters the loop mirror with built-in nonlinear optical waveguide through the second optical coupler 3, and transmits therein in the clockwise direction. The first signal light and the first control light transmitted in the clockwise direction enter the nonlinear optical waveguide 1 in the same direction as the pump light, and the cascaded sum frequency and difference frequency interaction occur in it, generating the clockwise transmitted At the same time as the idle light of the zero code, the position corresponding to the pump light in the middle part of the first signal light bit "1" is consumed, which will form a "pit" and introduce a nonlinear phase shift, and the first control light will correspond to these positions The amplified will form a "protrusion" and introduce a nonlinear phase shift. The return-to-zero code idle light, the first signal light and the first control light transmitted in the clockwise direction arrive at the fourth port D of the first optical coupler 2 The time-domain waveform is shown in the dotted line box A in Figure 4; the second signal light and the second control light transmitted in the counterclockwise direction are opposite to the pumping light. The phases cannot effectively contact each other during transmission, so the nonlinear effect occurring in the nonlinear optical waveguide 1 can be ignored, and no counterclockwise idle light is generated. When arriving at the fourth port D of the first optical coupler 2, the time-domain waveform of the second signal light is similar to the time-domain waveform of the input signal light, and there is no "pit" phenomenon and the introduction of nonlinear phase shift. The time-domain waveform of the control light is similar to the time-domain waveform of the input control light, and there is no "protrusion" phenomenon and the introduction of nonlinear phase shift, as shown in the dotted box B in Figure 4. At the fourth port D of the first optical coupler 2, the second path of signal light transmitted in the counterclockwise direction introduces a π phase shift relative to the first path of signal light transmitted in the clockwise direction, and the second path of signal light transmitted in the counterclockwise direction The control light also introduces a π phase shift relative to the first control light traveling in the clockwise direction. The two-way signal light interferes at the fourth port D of the first optical coupler 2 to obtain the return-to-zero code signal light, which is filtered by the first tunable filter 5 and then output; the two-way control light is transmitted to the fourth port of the first optical coupler 2 The return-to-zero code control light is obtained after interference at port D, and is output after being filtered by the third tunable filter 12 ; in addition, the return-to-zero code idle light is output after being filtered by the second tunable filter 11 .

Based on the inventive device shown in Figure 5, by appropriately changing the wavelengths of signal light, pump light, and continuous control light, it is convenient to realize the full range of single-channel-three-channel non-return-to-zero codes to return-to-zero codes with both input and output tunable Optical code conversion. The tunable principle is shown in Figure 6. The signal light 6, the pump light 7 and the control light 13 participate in the cascaded sum frequency and difference frequency interaction: the signal light 6 and the pump light 7 generate the sum frequency light 8 through the sum frequency process, At the same time, the difference frequency interaction between the control light 13 and the sum frequency light 8 obtains the converted idle light 14 . According to the principle of energy conservation, the wavelengths of signal light 6, pump light 7, sum frequency light 8, control light 13 and idle light 14 satisfy the following relationship:

SFG: 1/λ _SF ＝1/λ _S +1/λ _P

DFG: 1/λ _i = 1/λ _SF -1/λ _C (2)

SFG+DFG: 1/λ _i ＝1/λ _S +1/λ _P -1/λ _C

For the variable input signal light 6, as long as the wavelength of the pump light 7 is properly adjusted to keep the wavelength of the sum-frequency light 8 constant, thereby satisfying or approximately satisfying the quasi-phase matching condition of the sum-frequency process, the signal light 6 and pump light 7. Both the control light 13 and the idle light 14 can be tunable in a wide wavelength range. The wavelengths of the signal light 6 and the pumping light 7 and the wavelengths of the control light 13 and the idle light 14 are approximately symmetrically distributed with respect to the quasi-phase matching wavelengths in the frequency doubling process of the nonlinear optical waveguide. According to formula (2), when the wavelength of the sum-frequency light 8 remains unchanged, the wavelength of the pump light 7 is determined by the wavelength of the input signal light 6, and the wavelength of the converted idle light 14 is determined by the wavelength of the control light 13. Based on the second-order nonlinear effect of the cascaded sum frequency and difference frequency, by properly adjusting the wavelengths of the pump light 7 and the control light 13, it is very convenient to realize all-optical code conversion with tunable input and output from single-channel to three-channel , that is, variable input non-return-to-zero code signal light to return-to-zero code signal light, variable input non-return-to-zero code signal light to variable output return-to-zero code control light, and variable input non-return-to-zero code signal light to variable output Zero code idle light.

When it is necessary to realize the all-optical code conversion from single-channel to multi-channel non-return-to-zero codes to return-to-zero codes, multiple continuous control lights need to be input, which is still based on the cascaded sum frequency and difference frequency second-order nonlinear effect and interference principle. As shown in FIG. 7 , the working principle of the device of the present invention is: on the basis of FIG. 4 , the number of continuous control lights is further increased, that is, multiple continuous control lights are input. Similar to the case of inputting a single continuous control light, each time a continuous control light is input, a return-to-zero code converted idle light and a return-to-zero code control light will be generated correspondingly. Therefore, when n continuous control lights are input, n return-to-zero code converted idle lights and n return-to-zero code control lights, plus a return-to-zero code signal light , so that the all-optical code conversion from non-return-to-zero codes to return-to-zero codes of single-channel-(2n+1) channels is realized, and the wavelength of one channel remains unchanged before and after code conversion, while the wavelength of the other 2n channels before and after code conversion The wavelength is changed, that is, code conversion and wavelength conversion are realized at the same time.

As shown in FIG. 8 , the device of the present invention adds a wavelength division multiplexer 15 and first and second wavelength division multiplexers 16 and 17 on the basis of FIG. 6 . Wherein, the output terminal of the wavelength division multiplexer 15 is connected with one of the ports of the third optical coupler 9, and the other port on the same side of the third optical coupler 9 provides an input port of the non-return-to-zero code signal light to the outside, and the wavelength division The input end of the multiplexer 15 provides a plurality of input ports for continuous control light. The input end of the wave division multiplexer 16 is connected to the second tunable filter 11 , and its output end provides output ports for multiple return-to-zero code idle light. The input end of the wave division multiplexer 17 is connected to the third tunable filter 12, and its output end provides a plurality of return-to-zero code control light output ports. When arriving at the fourth port D of the first optical coupler 2, the position corresponding to the pumping light in the middle part of the first signal light bit "1" transmitted in the clockwise direction will form a "pits" and introduce abnormal Linear phase shift, while the first multiple continuous control lights transmitted in the clockwise direction correspond to these positions due to being amplified to form "protrusions" and introduce nonlinear phase shifts, the shapes of "pit" and "protrusion" Similar to the pulse shape of the pump light, in addition, the cascaded sum frequency and difference frequency process will also generate multiple return-to-zero code idle light, as shown in the dotted box A in Figure 7. There is no "pit" phenomenon and nonlinear phase shift in the middle part of the second signal light bit "1" transmitted in the counterclockwise direction, and there are no "protrusions" in the second multiple control lights transmitted in the counterclockwise direction phenomenon and the introduction of nonlinear phase shift, the time-domain waveform when it reaches the fourth port D of the first optical coupler 2 is shown in the dotted box B in FIG. 7 . When two channels of signal light transmitted clockwise and counterclockwise and two channels of multiple control lights interfere and output at the fourth port D of the first optical coupler 2, the second signal light transmitted in the counterclockwise direction is relatively The first path of signal light transmitted in the opposite direction introduces a π phase shift in total, and for any one of the multiple control lights, the second path of control light transmitted in the counterclockwise direction has a total of π phase shift compared with the first path of control light transmitted in the clockwise direction. A π phase shift is introduced. The result of the two-way signal light interference is to obtain the signal light output of the return-to-zero code, and the result of the two-way multiple control light interference is to obtain the control light output of multiple return-to-zero codes. Each continuous control light corresponds to generate a return-to-zero code idle light and a return-to-zero code control light. When n continuous control lights are input, n return-to-zero code idle lights and n return-to-zero code control lights can be obtained, and there is also one return-to-zero code signal light, so that a single channel-(2n+1) can be realized All-optical code conversion from channel non-return-to-zero code to return-to-zero code.

Based on the inventive device shown in Figure 8, by appropriately changing the wavelengths of the signal light, pump light and multiple continuous control lights, the single-channel-multi-channel non-return-to-zero code to return-to-zero code that can be tuned in both input and output can be easily realized All-optical code conversion. The tunable principle is shown in Figure 9, the signal light 6, the pump light 7 and multiple control lights 18 participate in the cascaded sum frequency and difference frequency interaction: the signal light 6 and the pump light 7 generate sum frequency light through the sum frequency process 8. At the same time, a plurality of control lights 18 interact with the sum frequency light 8 to obtain a plurality of converted idle lights 19 . According to the principle of energy conservation, the wavelengths of signal light 6, pump light 7, sum-frequency light 8, multiple control lights 18 and multiple converted idle lights 19 satisfy the following relationship:

SFG: 1/λ _SF ＝1/λ _S +1/λ _P

DFG: 1/λ _i1 = 1/λ _SF -1/λ _C1

SFG+DFG: 1/λ _i1 ＝1/λ _S +1/λ _P -1/λ _C1

... ...

...

...

DFG: 1/λ _m = 1/λ _SF -1/λ _Cn

SFG+DFG: 1/λ _m ＝1/λ _S +1/λ _P -1/λ _Cn

According to formula (3), by properly adjusting the wavelengths of the pump light 7 and multiple continuous control lights 18, it is very convenient to realize all-optical code conversion with tunable single-channel-multi-channel input and output. If n continuous control lights are input, it can realize single-channel variable input non-return-to-zero code signal light to single-channel return-to-zero code signal light, n-channel variable output return-to-zero code control light and n-channel variable output return-to-zero code Tunable all-optical code conversion for idle light.

Claims (3)

1, a kind of full optical code type conversion apparatus based on the non-linear optical waveguide annular mirror is characterized in that: this device comprises non-linear optical waveguide (1), first photo-coupler (2), second photo-coupler (3), tunable delay line (4) and first tunable optic filter (5); Non-linear optical waveguide (1) is PPLN optical waveguide or AlGaAs optical waveguide, and non-linear optical waveguide (1), first photo-coupler (2) and second photo-coupler (3) constitute the annular mirror of built-in non-linear optical waveguide;

One end of non-linear optical waveguide (1) links to each other with first port (G) of second photo-coupler (3), and its other end links to each other with first port (F) of first photo-coupler (2); A side relative with its first port (G) is provided with second, third port (H, K) in second photo-coupler (3), second port (H) of second photo-coupler (3) links to each other with tunable delay line (4), the input port of pump light externally is provided, the 3rd port (K) of second photo-coupler (3) links to each other with second port (E) of first photo-coupler (2), first, second port of first photo-coupler (2) (F, E) is positioned at the same side, and a side relative with it also is provided with the 3rd, the 4th port (C, D); The 3rd port (C) of first photo-coupler (2) is as the injection port of input nonreturn to zero code flashlight, the 4th port (D) with externally provide output port after first tunable optic filter (5) links to each other.

2, device according to claim 1 is characterized in that: this device also comprises the 3rd photo-coupler (9), the 4th photo-coupler (10), second tunable optic filter (11) and the 3rd tunable optic filter (12); Wherein, an end of the 3rd photo-coupler (9) links to each other with the 3rd port (C) of first photo-coupler (2), and two ports of opposite side externally provide the input port of nonreturn to zero code flashlight and stepless control light respectively; One end of the 4th photo-coupler (10) links to each other with the 4th port (D) of first photo-coupler (2), three ports of opposite side externally provide three output ports respectively with after first tunable optic filter (5), second tunable optic filter (11), the 3rd tunable optic filter (12) link to each other, and export return-to-zero code flashlight, return-to-zero code idle light and return-to-zero code control light respectively.

3, device according to claim 2 is characterized in that: this device also comprises wavelength division multiplexer (15) and first, second Wave decomposing multiplexer (16,17); Wherein, the output terminal of wavelength division multiplexer (15) links to each other with a port of the 3rd photo-coupler (9), the input end of wavelength division multiplexer (15) externally provides the input port of a plurality of stepless control light, the input end of Wave decomposing multiplexer (16) links to each other with second tunable optic filter (11), its output terminal externally provides the output port of a plurality of return-to-zero code idle light, input end the 3rd tunable optic filter (12) of Wave decomposing multiplexer (17) links to each other, and its output terminal externally provides the output port of a plurality of return-to-zero code control light.

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