WO2002005026A2 - Optical wavelength converter - Google Patents
Optical wavelength converter Download PDFInfo
- Publication number
- WO2002005026A2 WO2002005026A2 PCT/US2001/021550 US0121550W WO0205026A2 WO 2002005026 A2 WO2002005026 A2 WO 2002005026A2 US 0121550 W US0121550 W US 0121550W WO 0205026 A2 WO0205026 A2 WO 0205026A2
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- WO
- WIPO (PCT)
- Prior art keywords
- coupler
- optical
- paths
- wavelength converter
- output
- Prior art date
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2/00—Demodulating light; Transferring the modulation of modulated light; Frequency-changing of light
- G02F2/004—Transferring the modulation of modulated light, i.e. transferring the information from one optical carrier of a first wavelength to a second optical carrier of a second wavelength, e.g. all-optical wavelength converter
Definitions
- This invention relates generally to the field of optical communications and in particular to a method and apparatus for providing optical wavelength conversion employing cross phase modulation (XPM).
- XPM cross phase modulation
- the input signal is used to saturate the gain of the nonlinear element and thereby modulates the cw signal carrying the new wavelength.
- a strong input signal is used to modulate both the phase and intensity of a second signal. The modulation of this second signal is then exploited in an interferometric configuration for redirecting the signal from one output to an other.
- MI Michaelson
- MZI Mach-Zehnder interferometer
- an integrated wavelength converter with a monolithically integrated delay loop in a delayed interference configuration that needs only one SOA or other non-linear optical element coupled to the input fiber, a first coupler to arranged to split the output of the SOA or other non-linear optical element (i.e., an element that changes its material property, such as, for example, refractive index, absorption or gain, in the presence of a strong light signal) into two paths having controllable delay and phase shift characteristics, and at least one output coupler to combine the signals present on the two paths to provide the converter output.
- the SOA or other non-linear optical element i.e., an element that changes its material property, such as, for example, refractive index, absorption or gain, in the presence of a strong light signal
- at least one output coupler to combine the signals present on the two paths to provide the converter output.
- one embodiment of our inventive device has a monolithically integrated delay loop utilizing a coupler that has an asymmetric splitting ratio.
- the asymmetric coupler can be either the first coupler or the second coupler, or both.
- the non-linear optical element can, in addition to a semiconductor optical amplifier, be, for example, an electro-absorption modulator, a DFB laser, a gain clamped semiconductor optical amplifier, etc.
- Another embodiment of our invention has a coupler that does not require an asymmetric splitting ratio, and has either a gain element in one or both paths, an attenuation element in one or both paths, or the two in one or both paths.
- yet another coupler can be added to the wavelength converter to couple out part of the light in one or both of the paths, thereby obtaining a better extinction ratio.
- Figure 1 is a schematic drawing illustrating one embodiment of our inventive wavelength converter
- Figure 2(a) is a graph depicting time resolved output power as measured with a streak camera demonstrating the high extinction ratios and good quality of signals converted by the device of Figure 1;
- Figure 2(b) is an eye diagram of a 100 Gbit/s signal as measured with a 50
- Figure 3 is a graph showing measured BER of 100 Gbit/s wavelength converted signal vs. received preamplified input power
- Figure 4 is a schematic drawing illustrating another embodiment of our inventive wavelength converter in which a gain element and/or an attenuation element is used; and Figure 5 is a schematic drawing illustrating yet another embodiment of our inventive wavelength converter in which an additional coupler is added to the wavelength converter.
- FIG. 1 there is shown in schematic form a diagram depicting one embodiment, of our inventive optical wavelength converter 100. It includes a semiconductor optical amplifier (SOA) 110 monolithically integrated with a delayed interference loop 120 which may be formed by a tunable or fixed, but asymmetric splitting ratio coupler 130 and a coupler 140, e.g., a 2x2 or 1x2 coupler.
- SOA semiconductor optical amplifier
- a longer arm 125 of the delayed interference loop 120 provides a ⁇ t delay
- shorter arm 127 of the delay interference loop 120 includes a phase shifter 150.
- the device converts and reshapes a pulsed return-to-zero (RZ) input signal Pin at ⁇ l into a wavelength converted signal Pconv at ⁇ 2.
- the input signal Pin modulates the phase and the gain of co-propagating cw signal Pew in the SOA.
- the rise time of the phases shift in the Pew signal is almost instantaneous and limited by the pulse width of the Pin signal, whereas the fall time is limited by the slower, carrier recovery time.
- the power of an input pulse is chosen such that it modulates the phase of the cw signal by an amount of approximately +/- ⁇ or less.
- the Pew signal Upon exiting the SOA, the Pew signal is asymmetrically split between the longer arm 125 and the shorter arm 127 of the delayed interference loop 120 through the action of the asymmetric splitting ratio coupler 130. After traversing the respective arms of the interference loop 120, the signals are combined by coupler 140.
- the coupler 140 directs the Pew signal into a Pinv output port if the two signals in the two arms of the interference loop have a predetermined phase relation (additional phase-shifters on one or both of the arm can be used to provide the necessary offset phase shifts to obtain this predetermined phase relation), whereas it couples the signal into the Pconv output if an additional phase-shift of approximately ⁇ or less is induced.
- InGaAsP/InP wavelength converters may be grown by conventional Metal Organic Vapor Phase Epitaxy on (001) InP.
- the separate confinement hetero structure SOAs, having a length of approximately 1.2 mm may be grown first. Subsequently, the spotsize converters and passive waveguide layers are regrown using a butt coupling scheme to connect the two different layers in the same plane. Waveguides, couplers and phase shifters are defined by a wet etching step.
- the radius of the curved waveguides is substantially 250 ⁇ m and the total waveguide losses are below 3 dB.
- a doped, InGaAs layer is grown on top of the active SOA sections and phase-shifter sections to provide ohmic contacts.
- a representative size of such a packaging construction is approximately 6 x 1.3 mm. Subsequently, input and output ports may be fiber-pigtailed and the integrated device so constructed may be mounted with a temperature cooling unit into an additional (i.e., "butterfly") package.
- RZ input data signals P m were generated at a pseudo random bit sequence (PRBS) of 2 31 -1 at 100 Gbit/s.
- PRBS pseudo random bit sequence
- the phase shifter and the integrated tunable coupler were set such that the bit inverted and wavelength converted signal was directed to the output port.
- the bit inverted signals are more advantageous for high speed operation, since they contain all the signal pulse energy, whereas the non-inverted pulses are suppressed by the cross-gain modulation (XGM) that inevitably goes along with the cross-phase modulation (XPM).
- XGM cross-gain modulation
- XPM cross-phase modulation
- FIG. 2(a) A streak camera picture of the bit inverted and wavelength converted signal is depicted in Figure 2(a). Extinction rations iarger than 13 dB, as enabled by the integrated phase shifter and tunable coupler, are visible. Both the leading and trailing pulse transients are steep.
- Figure 2(b) shows eye diagrams of the 100 Gbit/s signal as recorded with a 50 GHz bandwidth photodiode. The eye diagrams of the second and ninth demultiplexed signals are shown as an example in the lower left and right inset of Figure 2(b).
- bit error rate (BER) performance is shown in Figure 3.
- the BER of the converted 100 Gbit/s signal was measured after demultiplexing back to 10 Gbit/s and feeding this signal to an optically pre-amplified pin receiver. Thus, the received power is measured for 10 Gbit/s.
- Figure 4 there is shown a schematic drawing illustrating another embodiment of our inventive wavelength converter in which a gain element and/or an attenuation element is used.
- non-linear element 410 performs the amplification function of SOA 110 of Fig. 1.
- the output of non-linear element 410 is applied to a coupler 430, which does not have to be asymmetric (as in the embodiment of Fig.
- Path 425 includes disposed therein a gain element 470, which can be a semiconductor optical amplifier, an optically pumped material, etc.
- Path 427 optionally includes a phase shifter 450, which corresponds to phase shifter 150 of Fig. 1, as well as an attenuation element 460, which can be an absorber or a radiating part of the waveguide, etc. Both the phase-shifter and/or the attenuator may be placed in one or the other, or both of the arms.
- the outputs of gain element 470 and attenuation element 460 are combined in a symmetric, asymmetric or tunable coupler 440, which, as a practical matter, can be a two by two coupler having complementary outputs, one of which is useful.
- the amount of gain provided by gain element 470 and the amount of attenuation provided by attenuation element 460 are advantageously adjusted, taking account of the characteristics of coupler 440, so that the extinction ratio of the output signal is optimized. For example, if coupler 440 is symmetric, then the gain provided by gain element 470 and/or the amount of attenuation provided by attenuation element 460 are adjusted so that the levels on the individual inputs to coupler 440 are essentially equal.
- Fig. 4 depicts the use of both a gain element 470 and an attenuation element 460, it is contemplated that the present invention may be arranged to use one or the other, as well as to use both. A clever combination of gain and attenuation elements might even be useful to eliminate additional phase-shifters on one or both arms.
- FIG. 5 is a schematic drawing illustrating yet another embodiment of our inventive wavelength converter in which an additional coupler is added to the wavelength converter.
- the elements are similar to those shown in Fig. 1, except that a non-linear element 510 is used in lieu of SOA 110.
- the outputs of symmetric, asymmetric or tunable splitting ratio coupler 530 are applied to a first path having a delay loop and to a second path optionally including a phase shifter 550 or one, the other or both of the arms.
- An additional coupler 580 is interposed in the second path, to remove a desired portion of light from the second path. This is done to adapt the signal intensities on the two interferometer arms in order to obtain good extinction ratios.
- the symmetric, asymmetric or tunable splitting ratio coupler 540 serves the same purpose as coupler 140 of Fig.1, i.e. it combines the light from the first and second paths, and makes the converted signal available: Note that the additional coupler can be placed in either or both of the first and/or second paths.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
Description
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2001275878A AU2001275878A1 (en) | 2000-07-07 | 2001-07-09 | Optical wavelength converter |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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US09/611,572 | 2000-07-07 | ||
US09/611,572 US6437905B1 (en) | 2000-07-07 | 2000-07-07 | Optical wavelength converter |
US09/809,401 US6646784B2 (en) | 2000-07-07 | 2001-03-15 | Optical wavelength converter |
US09/809,401 | 2001-03-15 |
Publications (2)
Publication Number | Publication Date |
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WO2002005026A2 true WO2002005026A2 (en) | 2002-01-17 |
WO2002005026A3 WO2002005026A3 (en) | 2002-06-06 |
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PCT/US2001/021550 WO2002005026A2 (en) | 2000-07-07 | 2001-07-09 | Optical wavelength converter |
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WO (1) | WO2002005026A2 (en) |
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2001
- 2001-07-09 WO PCT/US2001/021550 patent/WO2002005026A2/en active Application Filing
Non-Patent Citations (5)
Title |
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LEUTHOLD J ET AL: "100 Gbit/s all-optical wavelength conversion with integrated SOA delayed-interference configuration" ELECTRONICS LETTERS, IEE STEVENAGE, GB, vol. 36, no. 13, 22 June 2000 (2000-06-22), pages 1129-1130, XP006015367 ISSN: 0013-5194 * |
LEUTHOLD J ET AL: "ALL-OPTICAL MACH-ZEHNDER INTERFEROMETER WAVELENGTH CONVERTERS AND SWITCHES WITH INTEGRATED DATA- AND CONTROL-SIGNAL SEPARATION SCHEME" JOURNAL OF LIGHTWAVE TECHNOLOGY, IEEE. NEW YORK, US, vol. 17, no. 6, June 1999 (1999-06), pages 1056-1065, XP000908277 ISSN: 0733-8724 * |
LEUTHOLD J ET AL: "Cascadable dual-order mode all-optical switch with integrated data- and control-signal separators" ELECTRONICS LETTERS, IEE STEVENAGE, GB, vol. 34, no. 16, 6 August 1998 (1998-08-06), pages 1598-1600, XP006010130 ISSN: 0013-5194 * |
LEUTHOLD J ET AL: "Compact and fully packaged wavelength converter with integrated delay loop for 40 Gbit/s RZ signals" OPTICAL FIBER COMMUNICATION CONFERENCE. (OFC). TECHNICAL DIGEST POSTCONFERENCE EDITION. BALTIMORE, MD, MARCH 7 - 10, 2000, NEW YORK, NY: IEEE, US, vol. 4 OF 4, 7 March 2000 (2000-03-07), pages 218-220, XP002177936 ISBN: 0-7803-5952-6 * |
UENO Y ET AL: "SPECTRAL PHASE-LOCKING IN ULTRAFAST ALL-OPTICAL MACH-ZEHNDER-TYPE SEMICONDUCTOR WAVELENGTH CONVERTERS" JAPANESE JOURNAL OF APPLIED PHYSICS, PUBLICATION OFFICE JAPANESE JOURNAL OF APPLIED PHYSICS. TOKYO, JP, vol. 38, no. 11A, PART 2, 1 November 1999 (1999-11-01), pages L1243-L1246, XP000948550 ISSN: 0021-4922 * |
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WO2002005026A3 (en) | 2002-06-06 |
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