Fully reconfigurable optical add-drop multiplexer based on parallel configuration using Mach-Zehnder module

Reconfigurable optical add-drop multiplexer (ROADM) with the ability of dynamic configuration will be one of the core equipment for the future optical transport networks. This paper proposes an effective scheme for fully ROADM with parallel modularized structure and ability of upgrading. Each module consists of a Mach-Zehnder interferometer based on fiber Bragg grating (FBG), a 1 × 2 optical switch and a Y-model combiner. Optical signal with single wavelength or multiwavelength could be dropped or added at one drop port or add port by configuring the optical switch in each module. The proposed ROADM with four-stage parallel connection is designed and experimentally investigated to prove its performance and advantage in dynamic selection of the wavelengths and upgrading. It is also showed that this ROADM can also reduce the ununiformity of power at output port and drop port to improve the optical signal to noise ration (OSNR) of the whole system.     

Compact four-channel reconfigurable optical add-drop multiplexer using silicon photonic wire

We designed and fabricated a four-channel reconfigurable optical add-drop multiplexer based on silicon photonic wire waveguide, which is controlled through the thermo-optic effect. The effective footprint of the device is about 1000 × 500 μm². The minimum insertion loss including the transmission loss and coupling loss is about 10.7 dB. The tuning bandwidth is about 17 nm, the average tuning efficiency about 6.11 mW/nm and the tuning speed about 24.5 kHz.     

Novel optical add-drop multiplexer based on dual racetrack resonators

In this paper, we designed and fabricated a four-channel optical add-drop multiplexer (OADM) based on dual racetrack resonators. The size of the fabricated device is only 2400 μm × 500 μm. The fabricated device can effectively and perfectly realize the signals upload and download. The free spectral range (FSR) of OADM is about 15.2 nm. We take the spectral responses near 1555 nm as an example. When the device acts as an optical drop multiplexer, the minimum insertion loss is 4.481 dB and the maximum extinction ratio is 31.931 dB. The maximum adjacent channels crosstalk is -9.845 dB. When the device acts as an optical add multiplexer, the minimum insertion loss is 0.944 dB and all of the extinction ratios are bigger than 25 dB. The maximum crosstalk is -16.531 dB which indicates the crosstalk can be neglected.     

Tunable optical add-drop multiplexer based on long-period fiber gratings for coarse wavelength division multiplexing systems

We propose and experimentally demonstrate a voltage-controllable add-drop multiplexer with a tunable coupler based on long-period fiber gratings (LPFGs). The tunable coupler is based on cladding mode coupling between two parallel LPFGs with divided coil heaters, which controls the resonant wavelength positions of the two LPFGs. The wavelength tunability of the tunable coupler is measured to be -0.45 nm/degrees C in the temperature range from 20 to 120 degrees C. The large tuning range of optical signals (approximately 50.54 nm) from 1502.32 to 1552.86 nm, which covers both the short (S) and the conventional (C) bands, is achieved. The channel isolation is as high as approximately 40 dB. It has several advantages, including a broad tuning range of wavelength in both the S- and C-bands, high channel isolation, no backreflection, and so on.     

Tunable dual-wavelength fiber laser based on an opto-VLSI processor and four-wave mixing in a photonic crystal fiber

A stable wavelength and wavelength spacing tunable dual-wavelength fiber laser based on an Opto-very-large-scale-integration (Opto-VLSI) processor and four-wave mixing (FWM) in a high-nonlinear photonic crystal fiber is experimentally demonstrated. The results show that the line width of the tunable dual-wavelength fiber laser is 0.02 nm, and the wavelength spacing can be tuned from 0.8 nm to 4 nm with a 0.15 nm step. Under the influence of the FWM, the uniformity is below 0.6 dB and the measured side mode suppression ratio (SMSR) is above 45 dB.     

Multi-functional optical fiber sensor system based on a dense wavelength division multiplexer

We propose a novel and efficient multi-functional optical fiber sensor system based on a dense wavelength division multiplexer(DWDM).This system consists of an optical fiber temperature sensor, an optical fiber strain sensor, and a 48-channel DWDM.This system can monitor temperature and strain changes at the same time.The ranges of these two sensors are from-20℃ to 100℃ and from-1000 με to 2000 με, respectively.The sensitivities of the temperature sensor and strain sensor are 0.03572 nm/℃ and 0.03808 nm/N, respectively.With the aid of a broadband source and spectrometer,different kinds and ranges of parameters in the environment can be monitored by using suitable sensors.     

Add/drop applications in fiber ring networks based on a reconfigurable optical add/drop multiplexer in a re-circulating loop

A periodic add/drop system in a fiber ring network was investigated using a reconfigurable optical add/drop multiplexer (ROADM) in a re-circulating fiber loop. After seven cascaded add/drop nodes at every 150 km along the transmission, at bit error ratio (BER) equals to 10⁻⁹ and data rate of 10 Gbps, we observed a 2.5 dB power penalty for the passing through channels with 1050 km transmission distance, and 0.3 dB sensitivity penalty variation for the periodic add/drop channels at every 150 km, respectively.     

A novel reconfigurable radio-over-fiber system based on flexible optical devices

In this paper, a reconfigurable Radio over Fiber system based on optical switches, optical multimode interference power splitter and tunable optical filters is designed, which can achieve quadrature phase shift keying wireless modulation in optical domain and switch carrier frequency between 30 and 60 GHz. The scheme can make good use of bandwidth resource and realize signal transmission in fiber within 10 km.     

Sensor based on an integrated optical microcavity

A novel integrated optical sensor based on a cylindrical microcavity (MC) is proposed. A MC sustains so-called whispering-gallery modes (WGMs), in which the energy of the optical field can be efficiently stored. By monitoring the scattering intensity from the MC, one can detect minute changes in the refractive index of the WGM, for instance, as a result of analyte adsorption. Measurement of a change in refractive index of as little as 10(-4) is demonstrated experimentally. The MC-based integrated optical sensor may have a size of approximately 8mum , and it is rugged and inexpensive.     

Compact fluorescence depletion microscope system using an integrated optical element

The performance of a fluorescence depletion microscope system depends critically on the precise alignment of both the pump and the erase beams with the axis of the focusing objective lens. In this article we propose a technique with which the need for separate alignment of the pump and erase beams is eliminated. Besides being insensitive to alignment errors, our technique is much more compact than present systems, and can serve as a basis for a commercial fluorescence depletion microscope.     

Design of Hilbert transformers with tunable THz bandwidths using a reconfigurable integrated optical FIR filter

We present the design and analysis of a wideband and tunable optical Hilbert transformer (OHT) using a tunable waveguide-based finite-impulse response (FIR) filter structure by using the digital filter design method and the Remez algorithm. The tunable Nth-order waveguide-based FIR filter, which simply consists of N delay lines, N tunable couplers, N tunable phase shifters and a combiner, can be tuned, by thermally adjusting the tunable couplers and tunable phase shifters, to tune the bandwidth of an OHT using silica-based planar lightwave circuit (PLC) technology. To demonstrate the effectiveness of the method, the simulation results have an excellent agreement with the theoretical predictions. The tunable OHT can function as a wideband and tunable 90° phase shifter and thus has many potential applications. The two unique features of wideband characteristic (up to ~ 2 THz) and tunable bandwidth (THz tuning range) of the proposed OHT cannot be obtained from the existing OHTs.     

An all-silicone zoom lens in an optical imaging system

An all-silicone zoom lens is fabricated. A tunable metal ringer is fettered around the side edge of the lens. A nylon rope linking a motor is tied, encircling the notch in the metal ringer. While the motor is operating, the rope can shrink or release to change the focal length of the lens. A calculation method is developed to obtain the focal length and the zoom ratio. The testing is carried out in succession. The testing values are compared with the calculated ones, and they tally with each other well. Finally, the imaging performance of the all-silicone lens is demonstrated. The all-silicone lens has potential uses in cellphone cameras, notebook cameras, micro monitor lenses, etc.     

Silicon-on-insulator eight-channel optical multiplexer based on a cascade of asymmetric Mach-Zehnder interferometers

A monolithically integrated eight-channel optical multiplexer (Mux) with a 400 GHz channel spacing ~1550 nm is presented based on a silicon-on-insulator rib waveguide and an asymmetric Mach-Zehnder interferometer. All channels were optimized independently with integrated heaters. The fully tuned Mux shows an adjacent channel isolation of ~13 dB, an excess loss of ~2.6 dB, and a channel uniformity of ~1.5 dB over a 25 nm wavelength span. In addition, the phase tuning efficiency for different interlevel dielectric layer thicknesses and thermal crosstalk were investigated.     

Programmable multiple true-time-delay elements based on a Fourier-domain optical processor

A new technique to realize an array of multiple true-time-delay elements, which can be independently and continuously tuned, is reported. It is based on a WDM parallel signal processing approach in conjunction with a diffraction-based Fourier-domain optical signal processor. Programmable linear optical phase transfer functions are realized to obtain different electrical true-time delays. The technique can scale to a large number of wideband true-time-delay lines, with continuously tunable programmable delay. Results demonstrate multiple true-time-delay elements with independent tuning control and verify the concept by tuning the free spectral range of a microwave photonic notch filter. To our best knowledge, this is the first demonstration of multiple independently controllable true-time-delay lines for microwave photonic systems.     

An improved design of an integrated optical isolator based on non-reciprocalMach–Zehnder interferometry

Non-reciprocal rib waveguide structures can be used to realize integrated optical isolators. In this paper, we propose a concrete design for a Mach–Zehnder interferometer type isolator for TM modes. Just one of the arms, which are of equal length, is a non-reciprocal magneto-optic waveguide. The rest of the interferometer is reciprocal. Required fabrication tolerances are estimated, and the entire isolator is simulated by applying a finite difference beam propagation method.     

Chaotic signal generation and cancellation using a micro ring resonator incorporating an optical add/drop multiplexer

We propose a new design of a chaotic signal generation and cancellation system using an all fiber optic scheme. A system consists of a standard diode laser, a fiber optic micro ring resonator, and an optical add/drop multiplexer. When light from the diode laser is input into the fiber ring resonator, the chaotic signal can be generated by using the selected fiber ring resonator parameters and the diode laser input power. The required signal is obtained in the transmission link via the add/drop device by a specific user at the drop port. Simulation results obtained have shown the potential of application, especially, when the practical ring radius is 10 μm with the optical input power is in the range of the communication standard diode laser, for instance, when the coupling coefficients of the add/drop device are κ₁ = 0.01 and κ₂ = 0.01–0.9. When the add port of the add/drop device is employed, such a system can also be utilized for the multi user applications.     

Large-dispersion-tolerance optical signal transmission system based on temporal imaging

A novel optical signal transmission system, which is highly tolerant of dispersion of the transmission fiber, is proposed. The system employs a dispersion fiber and a phase modulator in both the transmitter and the receiver. We analyzed the characteristics of the system, using the temporal imaging concept, and found that the output optical pulse is insensitive to dispersion of the transmission fiber if the parameters of the system are set to hold a specific condition. We report simulation results that confirm these characteristics of the proposed system.     

Proposal and analysis of a reconfigurable pulse shaping technique based on multi-arm optical differentiators

We propose and numerically investigate an optical pulse re-shaping method based on multi-arm ultrafast optical differentiators. In this approach, the desired (arbitrary) optical pulse shape is synthesized by coherently overlapping different successive time derivatives of an input optical pulse (not necessarily a Gaussian-shape pulse), including the input pulse itself, with suitable relative weights. Time derivatives of (sub-)picosecond pulses can be obtained using first and higher-order ultrafast optical differentiators practically implemented with integrated waveguide or fiber-based linear filtering technologies. Different output pulse shapes can be generated from the same platform by properly programming the relative weights among the different pulse derivatives. The effective bandwidth of the output waveform is not necessarily limited by the input pulse bandwidth but rather it depends on the highest derivative order used for the pulse synthesis. Our results reveal that interesting transform-limited pulse shapes (including flat-top and parabolic waveforms) can be synthesized from Gaussian-like (e.g. Gaussian, sech) pulses using a simple and practical three-arm ultrafast differentiation system with amplitude-only relative weights.     

Robust design of an optical router based on a tapered side-coupled integrated spaced sequence of optical resonators

A novel (to our knowledge) scheme of an optical router/switch element, composed of a tapered side-coupled integrated spaced sequence of optical resonators, is proposed. It is based on a modified design of the ring sequence in which the resonance conditions are set by the single ring resonance and by the coherent feedback of the sequence of rings. This double condition yields robustness against fabrication defects, dense routing capability, and high switching efficiency.