CN1846159A - All-optical wavelength converter based on sagnac interferometer with an soa at asymmetric position - Google Patents

Abstract

According to at least one embodiment, a system comprises a Sagnac interferometric loop and a semiconductor optical amplifier (SOA) located at an asymmetric position on that loop, wherein the Sagnac interferometric loop and the SOA are operable to perform signal conversion on an input signal.

Description

Has All Optical Wave Converter at the based semiconductor image intensifer of the Sagnac interferometer of asymmetric position

Technical field

[0003] the present invention relates to wavelength Conversion in the optical fiber base communication system.

Background technology

[0004] in communication system, signal often transmits very long distance.The distance of this length may and be interfered owing to decay makes signal become degraded signal.Therefore, some systems utilize signal converter to receive degraded signal and recover its shape and amplitude.

[0005] in the past, optical fiber base communication system is utilized the electric signal transducer of receiving optical signals from light tranmitting medium, and light signal is changed over electric signal, recovers its shape and amplitude, and again electric signal is changed over the light that transmits by another kind of optical medium.The progress of optical fiber technology has allowed to develop light wavelength conversion operation, finishes conversion not changing under the condition that light signal becomes electric signal.Yet traditional optical transponder unit suffers the effect of pattern-dependent effect and weak extinction ratio.

Summary of the invention

[0006] the purpose of this invention is to provide a kind of like this system and method, wherein each embodiment utilization has Sagnac (Sarnia gram) interferometer of SOA to finish wavelength Conversion.Some typical embodiment utilize best interferometric phase biasing, can alleviate pattern-dependent effect and improve extinction ratio.According at least one embodiment, this system comprises: the Sagnac interferometric loop and on this loop the SOA (semiconductor optical amplifier) of asymmetric position, wherein Sagnac interferometric loop and SOA can finish conversion of signals to input signal.

[0007] content described above is summarized feature of the present invention and technological merit widely, in order to understand following detailed description of the present invention better.Other feature and advantage of the following description of the present invention constitute the theme of claims of the present invention.Those skilled in the art will appreciate that notion disclosed herein can be easily as other architecture basics that change or be designed for the identical purpose of realization the present invention with specific embodiment.The professional it is also understood that this suitable structure does not depart from the content of the present invention that appended claims limits.According to description below in conjunction with accompanying drawing, tissue that the present invention may be better understood and method of operating and other purpose and advantage, we believe that these are novel features of the present invention.Yet, it should be clearly know that each accompanying drawing that provides only is used for the purpose of illustration and description, rather than is construed as limiting the invention.

Description of drawings

[0008] in order to understand the present invention more completely, referring now to description, wherein below in conjunction with accompanying drawing:

[0009] Fig. 1 be according to each embodiment the Sagnac interferometric loop asymmetric position on the structure of SOA is arranged;

[0010] Fig. 2 (a) is that the typical case who can be used for some embodiments of the invention imports the NRZ signal graph;

[0011] Fig. 2 (b) is the signal graph that utilizes the conversion of XGM effect to produce;

[0012] Fig. 2 (c) is the signal graph that utilizes the conversion of Sagnac interferometer to produce according to each embodiment;

[0013] Fig. 2 (d) is the signal graph that utilizes the conversion of Sagnac interferometer to produce according to each embodiment;

[0014] Fig. 3 is the type signal converter that adopts the Sagnac interferometer according to each embodiment;

[0015] Fig. 4 (a) is the input signal eye pattern that can be used for one or more embodiment;

[0016] Fig. 4 (b) and (c) be wavelength converted signal eye pattern according to each embodiment;

[0017] Fig. 4 (d) is the translation data signal eye diagram that utilizes the XGM effect;

[0018] Fig. 5 (a) is the data pattern of input signal;

[0019] Fig. 5 (b) is a switching signal data pattern of utilizing the XGM effect;

[0020] Fig. 5 (c) is a switching signal data pattern of utilizing Sagnac interferometric loop shown in Figure 3;

[0021] Fig. 6 is the bit error rate (BER) measurement result of switching signal; With

[0022] Fig. 7 is the optical power loss of switching signal under different wave length.

Embodiment

[0023] in semiconductor optical amplifier (SOA) is placed on the Sagnac interferometric loop during off-centered position, the present invention shows a plurality of functions of utilizing short (RZ) light signal that makes zero, for example, the demultiplexing that is used for Optical Time Division Multiplexing (OTDM) system, light exchange and grouping route, light samples, photo reversal, or the like.For non-return-to-zero (NRZ) signal, it is possible utilizing waveform of the present invention to recover.In one embodiment, utilize the optical fiber base Sagnac interferometric loop that SOA is arranged on asymmetric position, the invention provides the All Optical Wavelength Conversion of NRZ signal.The phase bias that the analysis showed that interference is crucial for wavelength conversion operation.Compare with cross-gain modulation (XGM) fundamental wavelength converter, utilize the Sagnac interference structure, the present invention can reduce pattern-dependent effect and improve extinction ratio.As explained in more detail below, in one embodiment, utilize the Sagnac interferometric loop, the switching signal power loss that the 10Gb/s bit error rate (BER) measurement shows reduces.

[0024] though the wavelength conversion operation that other system adopts Mach-Zehnder and Michelson interferometer to show the NRZ signal with SOA, exemplary embodiments employing Sagnac interferometer described herein is as the NRZ wavelength shifter.Fig. 1 is Sagnac interferometric loop 100 structural drawing that SOA 101 is arranged on asymmetric position.Input signal 10 is divided into (CW) component 11 and (CCW) component 12 clockwise counterclockwise by 50:50 coupling mechanism 102.Because the asymmetric position of SOA 101 on loop 100, CW component 11 is by SOA 101 in different time transmission with CCW component 12.When getting back to 50:50 coupling mechanism 102, Polarization Controller 103 is used for the interference of control loop birefringence and formation when two components (CW component 11 and CCW component 12).

[0025] for convenience of description, we consider that the wave plate that postpones  and angle of orientation θ (being used to illustrate the loop birefringence) is arranged.CW component 11 and CCW component 12 stand phase shift  respectively _CWAnd  _CCWAnd gain G _CWAnd G _CCWInput light 10 is the linearly polarized lights with polarization direction α.The different phase shifts of CW and CCW light component and gain are included in the analysis of Sagnac loop 100, and the transmission of input optical signal can be expressed as follows:

(formula 1)

[0026] transmission of input optical signal can also be expressed as:

(formula 2)

Wherein $A=\sqrt{{({\cos }^2\left(2\mathrm{\θ}\right)+\cos \mathrm{\φ}{\sin }^2\left(2\mathrm{\θ}\right))}^2+{\left(\sin \mathrm{\φ}\sin \left(2\mathrm{\θ}\right)\sin \left(2\mathrm{\α}\right)\right)}^2}$

(formula 3)

With

(formula 4)

[0027] ordinary skill is appreciated that the transmission of above formula 1 and 2 can also be expressed as follows:

(formula 5)

With $T=\frac{1}{4}\{G_{\mathrm{CW}}^1+G_{\mathrm{CCW}}^2-2A{G}_{\mathrm{CW}}{G}_{\mathrm{CCW}}\cos ({\mathrm{\φ}}_{\mathrm{CCW}}-{\mathrm{\φ}}_{\mathrm{CW}}+{\mathrm{\φ}}_{\mathrm{\β}})\}$

(formula 6)

[0028] as shown in Equation 4, by adjusting input polarisation of light and loop birefringence, phase bias that can tuning interference.Utilize Polarization Controller, for example, Polarization Controller 103, the embodiment of the invention can provide the complete tunability of phase bias.The professional can understand, and has the whole bag of tricks can calculate gain and the phase change of light transmission by SOA.Because SOA101 is the asymmetric position on Sagnac loop 100, CW signal 11 arrives time ratio CCW signal τ=2 Δ x 12 morning of SOA 101 _SOA/ c _FiberTime delay, Δ x wherein _SOABe the skew of SOA 101 and loop 100 centers, and c _FiberIt is the light velocity in the optical fiber.

[0029] the typical input of Fig. 2 (a) expression NRZ signal 200, it is this shape of superelevation of 8mW that this signal has peak power.In one embodiment of the invention, can utilize following SOA parameter: live width enhancer=4.0, saturation power=1.0pJ, small-signal gain=20dB, SOA carrier lifetime=70ps and with the SOA skew=20ps of loop center.When not putting into the single SOA of Sagnac loop and be used for wavelength Conversion, the switching signal 201 that Fig. 2 (b) expression is produced by the XGM effect.The amplitude leyel of signal 201 metas " 1 " has very big fluctuating, and it represents the pattern-dependent effect that slow SOA regeneration rate produces.By reducing SOA release time, can address this problem, but it adds to the difficulties for the manufacturing of SOA.Employing can produce the switching signal 202 and 203 shown in Fig. 2 (c) and 2 (d) according to the Sagnac interference structure of the embodiment of the invention.In Fig. 2 (c), setting the phase bias of interfering is zero, and it is the condition of work that light exchange and regeneration are used.Fig. 2 (d) expression optimum phase is biased to-1.12 switching signal 203, compares with Fig. 2 (b), and it can reduce pattern-dependent effect and improve extinction ratio.

[0030] Fig. 3 represents can be used for the exemplary embodiments of the present invention of experiment purpose.Because this embodiment is an experimental, term " control " is used to be described in its conversion input NRZ signal before.This description only means that this signal also needs conversion, does not hint that this signal finishes the control function about any optical element in the signal converter 300.

[0031] signal converter 300 comprises Sagnac interferometer 301.SOA 302, and for example, working current is the Alcatel 1901 of 195mA, are connected to two output ports of 50:50 coupling mechanism 303.Can the skew (straight line 305 shown in) of tuned light tunable delay line (OTDL) 304 to adjust SOA302 and loop center subtly.Polarization Controller PC1 306 and PC2307 are used to adjust the light polarization direction along CW and the propagation of CCW direction.Utilize that length is 2 in the impulse source 309 ²³The continuous glistening light of waves can produce the NRZ data-signal in-1 the pseudo-random bit sequence modulated light source 308.Utilize Erbium-Doped Fiber Amplifier (EDFA) 311 to amplify the light modulated of output from modulator 320, and offer the control section of loop 301.The continuous glistening light of waves in the tunable laser source 312 enters the input port 30 of Sagnac loop 301, for example, and lasing light emitter HP 8168C.The have an appointment three dB bandwidth of 1nm of the tunable bandpass filters of using among this embodiment 310.In this EXPERIMENTAL EXAMPLE, the output of loop 301 is connected to error rate tester 313.Though in Fig. 3, specify each parameter and component models, but be understood that, the professional can determine when utilization has the Sagnac Ring Interferometer of asymmetric SOA, other parameter and/or component models can be used for producing suitable conversion of signals, and these different embodiment are within the scope of the invention.

[0032] in exemplary embodiments shown in Figure 3, control NRZ data-signal 31 (λ in the lasing light emitter 308 ₁=1545nm) average light power is 5.3dBm, and input light 30 (λ in the lasing light emitter 312 ₂=1535nm) luminous power is-2.7dBm.The wavelength of light 30 is determined the wavelength of output data 32 in the lasing light emitter 312.In this embodiment, adjust Polarization Controller PC1306 and PC2307 subtly to optimize wavelength converted signal.Fig. 4 (a) is the eye pattern of input NRZ signal 31 among this embodiment.Fig. 4 (b) and 4 (c) be respectively the skew of SOA and Sagnac loop center during for 23ps and 60ps wavelength converted signal 32 at the eye pattern of 1535nm.As a comparison, utilizing SOA is to implement under the optimization luminous power of the control data and the continuous glistening light of waves based on the wavelength Conversion of direct XGM effect.Fig. 4 (d) is this translation data signal eye diagram that utilizes the XGM effect.

[0033] Fig. 5 (a) is the input NRZ signal 500 data pattern figure that use in this embodiment.Fig. 5 (b) is the switching signal 501 data pattern figure that utilize the XGM effect, and Fig. 5 (c) is the switching signal 502 data pattern figure that utilize the Sagnac interferometric loop 301 that skew SOA 302 (23ps) is arranged.Comparison diagram 5 (b) and 5 (c), we can clearly be seen that, utilize the Sagnac interferometric loop can alleviate pattern-dependent effect.When the skew of SOA 302 and loop center is too big, can interacts between the phase ortho position, thereby switching signal is degenerated, shown in Fig. 4 (c).Note that the skew at SOA is under the situation of 60ps, the mistiming that CW component and CCW component arrive SOA 302 is 120ps.

[0034] Fig. 6 represents the measurement result of the bit error rate (BER).The power loss of switching signal 501 (utilizing the XGM effect) and switching signal 502 (utilizing Sagnac interferometric loop 301 among Fig. 3) is 10 ^-9Be respectively 4.3dB and 1.4dB down.Utilizing the XGM effect to cause switching signal 501 that the main cause of very high-power loss is arranged is pattern-dependent effect.Fig. 7 represents the optical power loss of switching signal 501 and 502 under different wave length.With the XGM wavelength shifter relatively, on asymmetric position, have the Sagnac interferometric loop 301 of SOA 302 shown in Figure 3 can reduce to surpass the power loss of 2dB.

[0035] though system shown in Figure 3 is a proving installation, embodiment of the present invention are feasible in actual applications.For example, in a scheme, the control of loop and output port can be connected to the optical fiber transmission line in the telecommunication system.The glistening light of waves (being similar to the light of lasing light emitter 312 among Fig. 3) can be input in the loop at input port continuously.As explained above, the continuous wave light wavelength is determined the wavelength of output signal.Therefore, the input signal on the optical fiber transmission line can utilize interferometric loop conversion, and outputs to and be transferred to the destination on the optical fiber transmission line again.Compare with the conversion that utilizes the XGM effect to finish on same signal, improved performance is being showed in this conversion aspect pattern-dependent effect and the extinction ratio.

[0036] advantage of some embodiment is, they are applicable in the optical networking that 10Gb/s and above conversion of signals can be provided, thereby are convenient to develop the current and following communication network.In fact, each embodiment can fully be integrated into the current and following optical networking.

[0037] in a word, utilize each embodiment of the optical fiber base Sagnac interferometric loop that SOA is arranged under 10Gb/s, to realize.Theoretical analysis shows that operation has significant effects to the phase bias of interference for wavelength.Compare with the wavelength Conversion of utilizing the XGM effect, utilize the switching signal of Sagnac interferometric loop that improved performance can be arranged shown in Fig. 1 and 3.

[0038] though we have described the present invention and advantage thereof in detail, should be understood that under the condition that does not depart from appended claims qualification spirit and scope of the invention, can make various variations, substitutions and modifications.In addition, scope of the present invention is not limited to the process in the specific embodiment described in the instructions, machine, and manufacture method, material is formed, device, method and step.According to corresponding embodiment described herein, the easy understanding of ordinary skill can utilize process existing or that develop later on, machine, manufacture method, material is formed, device, method or step, they are finished and describe the essentially identical function of corresponding embodiment herein or realize essentially identical result.Therefore, should comprise these processes in the scope of appended claims, machine, manufacture method, material is formed, device, method or step.

Claims (11)

1. system comprises:

The Sagnac interferometric loop; With

Semiconductor optical amplifier SOA on asymmetric position on this loop, wherein Sagnac interferometric loop and SOA can finish conversion of signals to input signal.

2. according to the system of claim 1, wherein Sagnac interferometric loop and SOA are included in the signal converter of optical communication net.

3. according to the system of claim 2, wherein optical communication net adopts Optical Time Division Multiplexing Technology.

4. according to the system of claim 2, wherein signal converter comprises:

50: 50 photo-couplers of communicating by letter with this loop;

Input signal source is used for communicating with the input of 50: 50 photo-couplers;

With the control signal source of photo-coupler coupling in 10: 90, wherein 10: 90 photo-couplers are communicated by letter with this loop, and can transfer control signal arrive this loop;

Two or more Polarization Controllers on this loop, the phase bias that they are interfered in can tuning this loop; With

Optic tunable lag line on this loop, it can adjust the skew of SOA and loop center.

5. according to the system of claim 1, wherein input signal is non-rz signal.

6. according to the system of claim 1, wherein converter output has low mode to rely on the switching signal of effect level, and wherein this low mode dependence effect level is lower than by the XGM effect of utilizing SOA converted input signal and the pattern-dependent effect level that does not have the Sagnac interferometric loop to produce.

7. according to the system of claim 1, wherein the Sagnac interferometric loop is to implement in fiber optic communication network.

8. method comprises:

Receive input optical signal and enter the Sagnac interferometric loop, wherein this loop comprises, the semi-conductor amplifier SOA on the asymmetric position on this loop;

In this loop input optical signal is divided into clockwise component and counterclockwise component, wherein each component arrives SOA in the different time;

Adjust polarization and loop birefringence, thus the phase bias of interfering in tuning this loop; With

The light signal of output conversion.

9. according to the method for claim 8, also comprise: adjust the skew of SOA and loop center.

10. according to the method for claim 8, wherein asymmetric position is the position that is different from loop center.

11. a system comprises:

Be used to receive the device that input optical signal enters the Sagnac interferometric loop, wherein this loop comprises the semi-conductor amplifier SOA on the asymmetric position that is positioned on this loop;

Be used at this loop input optical signal being divided into the clockwise component and the counterclockwise device of component, wherein each component arrives SOA in the different time;

Be used to adjust the birefringent device of polarization and loop, thus the phase bias of interfering in tuning this loop; With

Be used to export the device of the light signal of conversion.

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