Narrow-band Optical Signals Research Articles

Narrow bandpass filter with ultra-wide stopband in a hybrid metal-optical Tamm state structure

Narrow bandpass filters (NBPF) play an important role in quantum communications, optical biometrics and other fields. However, traditional narrow bandpass filters have limited stopband capabilities. Here, an ultrawide stopband narrow bandpass filter is realized by combining a metal layer with a distributed Bragg reflector (DBR) structure to simultaneously excite the upper and lower Tamm plasma polarization (TP) modes. Numerical simulations show that the transmittance of the filter exceeds 94 % at a wavelength of 1.55 μm with a full width at half maximum (FWHM) of 8 nm. In addition, the addition of metal layer Ge reduces the electric field intensity of the lower DBR structure, effectively reducing the side peak, making the filter stopband range reach 1 μm–20 μm, which is 32 times that of traditional NBPF. Our research results provide a method to obtain narrow-band optical signals from ultra-broad and strong background noise, which facilitates the field of quantum communication.

Integrating Triply‐ and Singly‐Bent Highly Flexible Crystal Optical Waveguides for Organic Photonic Circuit with a Long‐Pass‐Filter Effect

Fabrication of organic photonic integrated circuits (OPICs) greatly relies on crystalline materials with high mechanical flexibility and fluorescence (FL). Realizing an efficient OPIC with multiple photonic functions suitable for practical applications depends on creating complex circuit architectures. The mechanical and optical functions of crystals are susceptible to subtle differences in the molecular packing and, more importantly, the type of intermolecular interactions. Herein, an organic crystal (E)‐1‐(4‐(iodo)phenyl)iminomethyl‐2‐hydroxyl‐naphthalene (IPIN) exhibiting high flexibility under mechanical stress, bright green FL, and selective self‐absorbance of the blue part of its broadband FL signal is reported. IPIN microcrystal transduces its FL effectively even in its bent geometry. The significant crystal‐surface adhesion energy facilitates the micromechanical fabrication of a triply‐bent waveguide using a mechano(crystal)photonic approach, which is later integrated with a singly‐bent waveguide to create a unique OPIC. This futuristic OPIC delivers excitation position‐dependent and direction‐specific long‐pass‐filtered narrowband optical signals with different split ratios.

Photonic envelope detection and fiber transmission of 24 GHz IR-UWB signal based on phase modulation

A novel scheme for photonic envelope detection and fiber transmission of 24 GHz impulse radio ultra-wideband (IRUWB) signal is proposed based on phase modulator (PM). In the system, an optics assisted envelope detection unit (OAEDU) is used for filtering one of the first sidebands at the output of PM, then this narrow band optical signal transfers over single-mode fiber (SMF), and the envelope of 24 GHz IR-UWB signal is obtained after photodetection (PD) and low pass filter (LPF). The numerical simulation results show that the combination of PM and OAEDU can alleviate the fiber chromatic dispersion (CD) effectively. The proposed system may provide a simple and cost-effective solution for IR-UWB receiver.

Quantum frequency conversion in nonlinear microcavities

We study nonlinear microresonantors as potential implements for quantum frequency conversion of narrowband optical signals. Using silicon-nitride microdisks as a concrete example, we show that high-conversion performance can be achieved with relatively low pump power. Being chip integratable, such devices hold promise for use in large-scale quantum applications, including atomic-memory-based quantum repeaters.

Design and analysis of a dynamic spectral encoding code-division multiple-access communication system

An optical dynamic spectral encoding code division multiple access (CDMA) communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for a sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase-induced intensity noise (PIIN), and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping (FFH) system and a spectral amplitude coding (SAC) system that uses either a Hadamard code, a modified quadratic congruence (MQC) code, or a modified frequency hopping (MFH) code.

Design and analysis of synchronous dynamic frequency hopping code division multiple access communication system

An optical dynamic frequency hopping code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based of shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase induced intensity noise, and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping system and a spectral amplitude coding system that uses either a Hadamard code, a modified quadratic congruence code (MQC), or a modified frequency hopping code (MFH).

Fast frequency modulation optical code division multiple access communication system

An optical fast frequency modulation code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code named functional code is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The performance of this system is shown to be better compared with a fast frequency hopping and a spectral amplitude coding systems.

Long time-base temporal holography using fiber-optic tapped delay line diffractive arrays

We propose a temporal holography technique for realizing matched filter structures for arbitrary, narrow-band optical signals. By utilizing the extraordinarily large angular dispersion of a fiber-optic tapped delay line array, we show that it is possible to achieve temporal filtering of optical signals whose coherence times can exceed nanoseconds. This represents a significant improvement in the temporal reach of holographic filters, compared to grating-based methods.

Optical duobinary transmission systemwith no receiver sensitivity degradation

This Letter proposes a novel optical duobinary transmission system with no receiver sensitivity degradation. The transmitter yields a narrowband optical signal, and the receiver configuration is as simple as a binary IM-DD receiver. The feasibility of the proposed system is experimentally confirmed at 2.5, 5 and 10 Gbit/s.

A tapped delay line optical spectrum analyzer

A novel method for the spectral measurement of narrow-band optical signals is proposed. Temporal variations of an input signal are linearly converted into spatio-temporal variations across a coherent array of optical radiators via a tapped delay line wave-guiding structure. The power spectrum is estimated from the resulting diffraction pattern, with significantly larger angular dispersion than that obtainable using conventional gratings.

Injection traveling-wave laser amplifier based on a (GaAI)As double heterostructure

Theoretical and experimental investigations were made of single-pass amplification of narrow-band optical signals in resonator-free stripe heterostructures operated at room temperature. The following optophysical characteristics of laser amplifiers of this type were recorded: the maximum gain was 26 dB; the output signal/background ratio was up to 7 dB without spectral selection and up to 24 dB when an output filter with a pass band 0.1 nm wide was used; the sensitivity was of the order of 100 nW; the output signal power was up to 20 mW; the linear operation range was in excess of 20 dB; the response time in the linear region was less than 1 nsec. The experimental results were in satisfactory agreement with calculations.

Estimating the spectral width of a narrowband optical signal

Methods for estimating the spectral width of a narrowband optical signal are investigated. Spectral analysis and Fourier spectroscopy are compared. Optimum and close-to-optimum estimators are developed under the constraint of having only one photodetector.

Amplification of a narrow-band optical signal in an active waveguide

An investigation was made of amplification in an optically pumped single-mode planar dielectric waveguide activated with rhodamine B. Radiation emitted from a distributed–feedback laser of spectral width 0.2 run was used as the input signal. Measurements were made of the power and spectrum of the output signal as a function of the input signal level. A gain of 100 was obtained for the ratio of the signal to background exceeding 10. The method for filtering out the spontaneous background was considered.

Performance of an Ideal Quantum Receiver of a Coherent Signal of Random Phase

An ideal quantum receiver is to detect a coherent narrow-band optical signal in the presence of thermal background radiation. Curves are given both of the average probability of error in a binary communication system transmitting O's (blanks) and 1's (pulses) with equal probabilities, and of the probability of detection for various fixed values of the false-alarm probability.