Optical Wavelength Conversion Research Articles

On-Chip SOI Delay Line Bank for Optical Buffers and Time Slot Interchangers

We demonstrate integrated silicon-on-insulator (SOI) spiral waveguides with record-high 2.6-ns/mm2 on-chip delay efficiency performing as delay bank stage in variable optical delay buffering and time-slot interchanger applications with 10-Gb/s optical packets. The micro-scale SOI chip comprises three integrated waveguide delay elements of different lengths, providing variable delays of 6.5, 11.3, and 17.2 ns, respectively. Utilizing two semiconductor optical amplifier Mach-Zehnder interferometer wavelength converters and on-chip packet delay, error-free on-chip variable delay buffering from 6.5 to 17.2 ns and successful time-slot interchanging for 10-Gb/s optical packets are presented.

All-Optical Wavelength Conversion Based on Four-Wave Mixing in Dispersion-Engineered Silicon Nanowaveguides

We demonstrate experimentally all-optical wavelength conversion based on four-wave mixing in dispersion-engineered silicon nanowaveguides with a picosecond pulse pump. We find that the conversion efficiency is significantly limited by nonlinear losses induced by the two-photon absorption and freecarrier absorption. Using a picosecond pulse pump centered at 1,550 nm, we show that the input continuous-wave signals can efficiently be converted into a broadband idler pulse in silicon waveguides with various dimensions. Conversion efficiencies versus signal wavelengths are different for silicon waveguides with different dimensions due to the variation in the phase mismatch; we obtain a conversion efficiency of – 32 dB in silicon nanowaveguides with a length of 5.8 mm. Such on-chip optical wavelength converters can find important potential applications in highly-integrated optical circuits for all-optical ultrafast signal processing.

Demonstration of Optical FEC Coding Scheme With Convolutional Code Consisting of a Signal Source

In this letter, we experimentally demonstrated an all-optical forward error correction (FEC) coding scheme with the $(7, 5)_{8}$ convolutional code using a single signal source to compensate time-dependent noise. The proposed coding scheme was comprised of optical XOR gates, delay lines, and optical wavelength converters, which are based on four-wave mixing in highly non-linear fibers. The temporal waveforms of the optical FEC coding scheme were experimentally achieved for 10 Gb/s return-to-zero differential phase shift keying (RZ-DPSK) signals modulated with $2^{23}-1$ , and the obtained idler signals accurately corresponded to the $(7, 5)_{8}$ code between any input signals. Under the optimized conditions of operational wavelengths, the proposed scheme theoretically offered 4.0 and 3.5 dB net coding gains for the conditions of BER $\geq 10^{-8}$ and BER $= 10^{-9}$ , respectively, owing to its small power penalties.

Optimizing OSSB Generation Using Semiconductor Optical Amplifier (SOA) for 5G Millimeter Wave Switching

Millimeter waves (MMWs), operating at 30–300 GHz band, are very promising to the next-generation 5G wireless communication systems, enabling data rates of multi Gbps per user. Photonic technology is increasingly considered to play a key role in a wide range of MMW devices, modules, and subsystems that are essential to successfully build next generation MMW-based 5G networks. This work considers the switching function of MMWs exploiting nonlinearity in photonic devices. In this paper, we perform a systematic investigation of the optimum operating conditions that enable an optical single sideband wavelength conversion, by exploiting the nonlinear effects in a semiconductor optical amplifier (SOA). This principle of switching carefully exploits SOA’s four-wave mixing, cross-gain modulation in addition to self-phase modulation effects. The key parameters under investigation include the injection current, the wavelength spacing between the probe and the pump signals in addition to their respective powers. We experimentally determine the optimal operating conditions that maximize the sideband suppression ratio and simultaneously reduce the useless left sideband signal intensity, leading to a dispersion free transmission in optical fiber. Further, we experimentally demonstrate a photonic-based MMW switch of MMW signals having 30 GHz frequency and carrying 3 Gbaud/QPSK modulated signals. A 14-dB sideband suppression ratio of modulated signal is reported.

TYPE 1 & TYPE 2 OPTICAL LIMITING STUDIES IN DISPERSE ORANGE-25 DYE-DOPED PMMA-MA POLYMER FILMS USING CW LASER

Materials with exceptional third-order nonlinear optical properties are critical to the continuing development of photonics and electro-optical devices such as those used in optical communications, networking, the optical computation for signal processing, and data storage devices. The nonlinear optical material research is generally focussed on improving the efficiency of optical wavelength conversion, optical amplification, nonlinear absorption, refractive index changes etc. which are input light intensity dependent. During last few years, the organic dye-doped polymer films are getting more attention due to their advantages in fabricating optimum photonics devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an azo dye Disperse Orange-25 (DO-25) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods for continuous wave (CW) laser input. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input power using continuous wave (CW) laser beams of 532 nm wavelength.The nonlinear absorption coefficient, nonlinear refractive index, and saturated output power for type 1 and type 2 optical limiting are determined.

Reconfigurable high-speed optical fibre networks: Optical wavelength conversion and switching using VCSELs to eliminate channel collisions

Abstract We experimentally provide an alternative solution to channel collisions through up-wavelength conversion and switching by using vertical cavity surface-emitting lasers (VCSELs). This has been achieved by utilizing purely optical wavelength conversion on VCSELs at the low attenuation, 1550 nm transmission window. The corresponding transmission and bit error-rate (BER) performance evaluation is also presented. In this paper, two 1550 nm VCSELs with 50–150 GHz channel spacing are modulated with a 10 Gb/s NRZ PRBS 2 7 -1 data and their interferences investigated. A channel interference penalty range of 0.15–1.63 dB is incurred for 150–50 GHz channel spacing without transmission. To avoid channel collisions and to minimize high interference penalties, the transmitting VCSEL with data is injected into the side-mode of a slave VCSEL to obtain a new up converted wavelength. A 16 dB extinction ratio of the incoming wavelength is achieved when a 15 dBm transmitting beam is injected into the side-mode of a −4.5 dBm slave VCSEL. At 8.5 Gb/s, a 1.1 dB conversion and a 0.5 dB transmission penalties are realized when the converted wavelength is transmitted over a 24.7 km G.655 fibre. This work offers a low-cost, effective wavelength conversion and channel switching to reduce channel collision probability by reconfiguring channels at the node of networks.

High-Brightness Continuously Tunable Narrowband Subterahertz Wave Generation

We report on the generation of high-brightness (high peak power and narrow linewidth) continuously tunable subterahertz waves by optical parametric wavelength conversion using lithium niobate as a nonlinear optical crystal. The high-brightness subterahertz waves were achieved by expanding the interaction volume of the pumping beam and the idler wave, as well as the subterahertz wave, during wavelength conversion and by injecting the seeding beam into the idler wave. We could continuously tune the wavelengths of the generated subterahertz waves by controlling the angle and wavelength difference between the pumping and injection seeding beams to satisfy the noncollinear phase-matching conditions. The high-brightness (maximum peak output power, linewidth) and tunable range were about 10 MW/sr· cm 2 (>7 kW, <;5 GHz), and 760-150 μm (0.39-2 THz), respectively.

On the Use of Terminal and Inline Conversion in Planar Optical Interconnection Networks

Optical wavelength converters (WCs) are used in the design of most optical interconnection networks to improve blocking performance. Typical network architectures make use of WCs at the terminal of the network (i.e., at the input and/or output ports). Recently, inline conversion has been introduced where WCs are deployed and shared between the stages of the network. Sharing conversion among stages can lead to architectures with reduced complexity and hence lower cost. However, sharing inline conversion requires crossovers of interstage links to enter and exit the shared inline converters. As a result, inline conversion can be difficult to implement in planar switching networks with no crossover between interstage links. In this paper, we study, for the first time to the best of our knowledge, the use of combined terminal and inline WCs in planar optical interconnection networks. In particular, we show that terminal conversion has limited scalability even when fixed-range WCs are used. Accordingly, we propose a new design approach that improves scalability while preserving the noncrossover property of planar interconnection networks. It is shown that all conversion processes in the new design are independent of the number of wavelengths in the network, and hence high scalability is achieved.

Optical Wavelength Converters Based on Four Wave Mixing in SOA-MZI Configuration

Wavelength converter plays an important role for increasing the capacity and flexibility of future broadcast network. This paper investigates the performance of a 10Gb/s the SOA based FWM wavelength converter. All performances are analyzed in terms of its shifted wavelength conversion efficiency, Q-factors and converted signal powers. The converters are modeled and simulated using Optisystem7 Software, by varying the probe signal wavelength and power. It was found that conversion efficiency and OSNR of the converted signal both decreased at large detuning wavelengths. Similarly, higher total SOA input powers worsened the conversion efficiency, but steadily improved the OSNR. FWM wavelength converter had the lowest conversion efficiency for CW sources.

基于光子晶体光纤的受激拉曼散射全光波长转换研究

基于光子晶体光纤的受激拉曼散射全光波长转换研究

10 Gbps Externally Modulated XGM Based Wavelength Conversion Using SOA

This paper proposes a method for All Optical Wavelength Conversion using semiconductor optical amplifier at 10Gbps. The system is demonstrated for Cross Gain Modulation (XGM) process of SOA, which is the simplest wavelength conversion technique that takes the advantage of non linear gain suppression mechanism in SOA. The system performances are analyzed using Q factor and Extinction Ratio of the eye diagram. The input pump power is varied from 2 dBm to 5 dBm; also the extinction ratio of Mach-Zehnder modulator is varied from 30 dBm to 60 dBm. Maximum Q Factor of 11.86dB is obtained for a maximum output signal power 23.94 dBm. Minimum Q Factor obtained is 7.58dB for a minimum output signal power 23.15 dBm. The extinction ratio falls from 18.56dB to 16.63dB as the input conditions are varied.

基于光子晶体光纤的受激拉曼散射全光波长转换研究

基于光子晶体光纤的受激拉曼散射全光波长转换研究

Pump linewidth requirements for processing dispersion-altered DQPSK signals using FWM

We report on a potentially deleterious issue regarding the four-wave mixing (FWM)-based processing of dispersion-altered signals. We estimate the baudrate-dependent pump linewidth tolerances by calculating the extra optical signal to noise ratio (OSNR) penalty with respect to the propagation distance. We find that the issue is not important for 10Gbaud differential quadrature phase shift keying (DQPSK) signals, though for 28Gbaud (and 56Gbaud) DQPSK signals we find that the pump linewidth requirements to implement FWM based optical signal processing needs to be in the sub-MHz range in order to avoid excessive OSNR penalties for the case of dispersion-altered signals. These results are pertinent for systems employing FWM, which could be all—optical wavelength converters for packet switching or mid-span spectral inversion techniques.

Broad-Range tunable optical wavelength converter for next generation optical superchannels

A broad-range tunable all optical wavelength conversion scheme that is based on a dual driven Mach-Zehnder modulator with an integrated microwave generator to tune the channel spacing along the entire C band, is proposed. Successful signal demodulation up to 8 wavelength conversions, in steps of 50-400 GHz of 100 Gbps Nyquist QPSK channels with configurable channel spacing is reported. The proposed wavelength conversion scheme enables flexible wavelength routing on gridless optical networks, as can be seen in the Superchannels with a BER lower than 10&lt;sup&gt;-13&lt;/sup&gt;.

Investigation on optical wavelength conversion based on SPM using triangular-shaped pulses

Abstract A photonic triangular-shaped pulse train is generated based on optical subcarrier modulation and harmonic fitting. After modulated by an amplitude modulator, a single symmetrical triangle-shaped pulse is extracted to investigate the optical wavelength conversion caused by the self-phase modulation effect in a high nonlinear fiber (HNLF). Then two frequency shifts are induced and gradually separated from the original pulse frequency. The energy has been transferred to the two new frequencies efficiently and wavelength conversion is realized. It is also found that the wavelength conversion is proportional to the input power level of the triangular-shaped pulse, the fiber length and nonlinear coefficient of the HNLF and the spectra intensity evolution over time.

Impairments Computation for Routing Purposes in a Transparent-Access Optical Network Based on Optical CDMA and WDM

AbstractOptical access networks are becoming more widespread and the use of multiple services might require a transparent optical network (TON). Multiplexing and privacy could benefit from the combination of wavelength division multiplexing (WDM) and optical coding (OC) and wavelength conversion in optical switches. The routing process needs to be cognizant of different resource types and characteristics such as fiber types, fiber linear impairments such as attenuation, dispersion, etc. as well as fiber nonlinear impairments such as four-wave mixing, cross-phase modulation, etc. Other types of impairments, generated by optical nodes or photonic switches, also affect the signal quality (Q) or the optical signal to noise ratio (OSNR), which is related to the bit error rate (BER). Therefore, both link and switch impairments must be addressed and somehow incorporated into the routing algorithm. However, it is not practical to fully integrate all photonic-specific attributes in the routing process. In this study, new routing parameters and constraints are defined that reflect the distinct characteristics of photonic networking. These constraints are applied to the design phase of TON and expressed as a cost or metric form that will be used in the network routing algorithm.

Optical Phase Erasure and Wavelength Conversion Using Silicon Nonlinear Waveguide With Reverse Biased PIN Junctions

We demonstrate the optical phase erasure and wavelength conversion based on the nontransparency four-wave mixing simultaneously using the integrated silicon waveguide with reverse biased PIN junction. By optimizing the design of the waveguide, a conversion efficiency of $-$ 12 dB can be achieved with 3-dB conversion bandwidth of 15 nm. For demonstration, the phase information of the phase-shift keying signal at 10 Gb/s is erased. The simulated and measured constellations and eye diagrams validate the successful operation.

All Optical Wavelength Conversion of Nyquist-WDM Superchannels Using FWM in SOAs

In this paper, the performance of all-optical wavelength conversion (WC) of Nyquist-WDM superchannels is investigated for future implementation in optical networks. We consider advanced modulation formats of DQPSK and 16-QAM for the subchannel modulation format achieving raw bit rates of 448 and 896 Gb/s, respectively. We demonstrate through simulations the WC of Nyquist-WDM superchannel using degenerate and nondegenerate four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). We consider the effects of raised cosine (RC) and root raised cosine (RRC) signal pulse shaping within the wavelength conversion process. We find that the performance of the converted superchannel is severely impaired by crosstalk due to cross-gain modulation of the pump by the superchannel. Optimum performance of the converted superchannel is achieved by setting the detuning between the continuous-wave pump and the central wavelength of the superchannel to be around 200 GHz and using pumps of double the gain saturation power of the SOA with 23 dB pump to signal power ratio.

Nonresonant Excitation Inside an Ultrahigh- &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$Q$&lt;/tex-math&gt;&lt;/inline-formula&gt; Nanocavity

Achieving on-chip optical wavelength conversion is a long-pursued object with fundamental difficulty in integrated photonics. As a step toward this goal, we theoretically and numerically demonstrate that wavelength conversion can be realized in a high-Q photonic crystal nanocavity, without any phase matching and high power requirement. The wavelength conversion efficiency of nearly 100% is achieved for a broad conversion range, and the mechanism is attributed to the dynamic interaction between the trapped light and an ultrahigh-Q cavity.

Few‐Layer Topological Insulator for All‐Optical Signal Processing Using the Nonlinear Kerr Effect

Topological insulators (TIs) are a new quantum phase of matter with topologically protected surface metallic states inside the insulating bulk states. Due to their unique single Dirac cone surface state, relatively low sheet resistance, and broadband optical operation, they have attracted enormous interests in both electronics and optics. Out of those above‐mentioned applications, electronic devices are seeking most attention until now. Here the experimental prototype for light processing device, TI‐coated microfiber (TCM), is demonstrated. Owing to the large Kerr coefficient of TI, TCM could operate as an effective optical Kerr switcher and broadband wavelength converter at the telecommunication band. This device could be well integrated with current high‐speed fiber optic communication networks and might well provide an approach for all‐optical signal processing through nonlinear processes. It is anticipated that few‐layer topological insulator might afford new opportunities for nonlinear photonic applications, especially in all‐optical routing, optical multiplication frequency, etc.