Carrier-to-noise Ratio Research Articles

Optical Reading From Videotapes Using Magnetic Garnet Film

In order to greatly increase the speed at which videotapes are read, we propose an optical reading method using a magnetic garnet film. This method allows several data tracks to be read in parallel. In order to realize the optical reading of data, the magnetic garnet films need to have not only high enough resolution for all data to be transferred from the videotape, but also a large Faraday coefficient for data to be reproduced with a high carrier-to-noise ratio (CNR). We have constructed trial films with a Faraday rotation angle of approximately 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> per micrometer film thickness when a green laser is used. The data patterns transferred from a D-3 format videotape were clearly observed using a polarizing microscope. An experiment to reproduce videotape data was carried out at a tape speed of 0.367 m/s, and a CNR of over 30 dB was achieved for a bit-length of 0.385 mum. The film had a constant real permeability over a frequency range of 40 MHz, which corresponds to a tape speed of 353x with respect to the D-3 system.

Employing split-band and only one sideband techniques to improve fiber optical CATV system performance

A directly modulated NTSC 77-channel fiber optical CATV transport system based on split-band and only one sideband techniques is proposed and demonstrated. Good performances of carrier-to-noise ratio (CNR), composite second-order (CSO) and composite triple beat (CTB) were obtained in our proposed systems over a 100 km standard single-mode fiber (SMF) transmission. Since an expensive externally modulated transmitter, sophisticated optical single sideband (SSB) modulation and stimulated Brillouin scattering (SBS) suppression techniques are not used, it reveals an outstanding system with simplicity and economic advantages over that of an externally modulated transport system.

Optical recording characteristics of molybdenum oxide films prepared by pulsed laser deposition method

Molybdenum-oxide (MoO 3)films were deposited on glass substrates (Corning #7059 with an area of 26 × 38 mm 2) by pulsed laser deposition using an ArF excimer laser. It was found that after annealing at 340 °C for 10 min, the film thickness became 2.3 times that (approximately 30 nm) of the as-deposited film thickness. The difference in the transmittance, Δ T, between the annealed state and the as-deposited state was about 40% at a wavelength of 400 nm. X-ray diffraction spectra indicated that oxygen was absorbed into the MoO 3 films through the annealing process. From revolution testing of 30 nm-thick MoO 3 films without a protective layer deposited on a polycarbonate DVD-R disk substrate (120 mm ϕ, 0.6 mm thickness), a write peak-power dependence of carrier-to-noise ratio (CNR) (recording on-land, at λ = 406 nm, NA = 0.65) of the 3T signal (58.5 MHz) was measured at a linear velocity of 5 m/s and a read power of 0.6 mW. Consequently, CNR near 50dB was obtained in the wide write-power margin Δ P of 7 mW (at peak powers between 3.5 and 10.5 mW). From SEM observations, it was recognized that bits of 0.25–0.30 μm size, corresponding to a storage capacity of 7–10GB/in 2 in the case of NA = 0.65, were formed. For the sample structure with an Al 2O 3 protective layer of ~ 20 nm thickness, a CNR near 50dB was obtained in the peak-power margin Δ P of 12 mW (at peak powers between 6.0 and 18.0 mW). Larger values of the CNR can be obtained if the film thickness of each layer including both the active and protective layers is optimized.

Blu-ray Type Super-Resolution Near-Field Phase Change Disk with In2Ge8Sb85Te5 Mask Layer

A new mask layer of In2Ge8Sb85Te5 was developed and used on super-resolution near-field phase change optical disks (super-RENS). The thermal and optical properties of the mask layer were investigated. Thermal analysis showed higher crystallization temperature and activation energy but lower melting temperature than Ge2Sb2Te5 phase change material. Ultra-fast crystallization within 30 ns was obtainable using a pulsed high-power laser beam of 405 nm wavelength. The recording performance of the new structure was evaluated on an optical recording system with a numerical aperture of 0.85 and a 405 nm blue-violet laser diode. Carrier-to-noise ratio (CNR) of 32, 25, 15, and 10 dB were obtained for 80, 50, 40, and 30 nm mark trains, respectively. Readout thermal stability of 20,000 cycles was realized for 80 nm mark trains. These performances were by far the highest obtainable for blu-ray aperture-type super-RENS disk.

Stability and Signal Quality Enhancement of Super-Resolution Disc by Pre- and Post-Curings of Readout Layer

By applying pre- and post-curings to the fabrication of a readout layer of a super-resolution disc that uses a phase-change material for the readout layer, the short-term readout stability and the signal quality were greatly improved. We obtained a disc whose signal degradation does not occur after the curing and the noise level was reduced by 1–2 dB, carrier-to-noise ratio (CNR) was enhanced by 2–3 dB, and the jitter was enhanced by 2–3%. Moreover, for long-term readout stability, we chose GeN interfacial layers between the readout and dielectric layers and obtained stable signal quality in terms of CNR of up to over 0.2 million readings.

Super-Resolution Near-Field Blue Laser Type Optical Disk with Modified Coumarin Dye Recording Layer and Poly(methyl methacrylate) Contrast Enhanced Layer

A new coumarin derivative with blue light absorption was designed and synthesized. The absorption properties and thermal stability of the coumarin derivative were discussed. We also studied the characteristics of a super-resolution near-field blue laser type optical disk with a modified coumarin recording layer and a poly(methyl methacrylate) (PMMA) contrast enhanced layer. A sample disk, which consists of a spin-coated coumarin derivative recording layer and a PMMA contrast enhanced layer, showed excellent recording and readout characteristics with a carrier-to-noise ratio (CNR) of about 33 dB for a mark length of 100 nm (laser wavelength = 405 nm, numerical aperture = 0.65). These results indicate that the coumarin derivative dye is a promising candidate for optical recording by a super-resolution near-field structure (super-RENS) technique.

CATV/ROF transport systems based on −1 side mode injection-locked and optoelectronic feedback techniques

A directly modulated CATV/radio-on-fiber (ROF) transport system based on −1 side mode injection-locked and optoelectronic feedback techniques is proposed and demonstrated. Good performances of carrier-to-noise ratio (CNR), composite second-order (CSO) and composite triple beat (CTB) were obtained for the CATV band, as well as low third-order intermodulation distortion to carrier ratio (IMD3/C) and bit error rate (BER) values were achieved for the intelligence transport system (ITS) application. This demonstrated CATV/ROF transport system is a promising candidate for long-haul fiber transmission applications.

Radio-on-hybrid WDM transport systems based on mutually injection-locked Fabry–Perot laser diodes

A radio-on-hybrid wavelength-division-multiplexing (WDM) transport system employing mutually injection-locked Fabry–Perot laser diodes (F–P LDs) is proposed and demonstrated. System performances evaluated by carrier to noise ratio (CNR), composite second order (CSO), composite triple beat (CTB), bit error rate (BER), and third-order intermodulation distortion to carrier ratio (IMD 3/C) for simultaneous transmission of CATV/LAN/ITS are improved. Our proposed systems are relatively simple and potentially low cost due to the use of mutually injection-locked F–P LDs as broadband light source (BLS).

An Integrated Pulsed Interference Mitigation for GNSS Receivers

The E5/L5 frequency band for the new Global Navigation Satellite System (GNSS) signals is crowded with aeronautical pulsed emitters. This results in severe degradation of the performance of GNSS receivers. This paper describes a novel technique for estimating and suppressing time-varying pulsed interference signals such as the Distance Measuring Equipment (DME)/Tactical Air Navigation (TACAN) signals generated by these pulsed emitters. The proposed technique involves the integration of the time-based pulse blanker and the wavelet-based interference mitigation technique. Aviation is the key application considered although many other applications such as transport management and navigation, environmental monitoring, and telecommunications would benefit. A performance assessment of the new technique is carried out by determining the degradation of the carrier-to-noise ratio (CNR) at the output of the correlator. The performance of the new technique is compared with the traditional time domain pulse blanking approach. The results show that the proposed technique performs better than both the time domain pulse blanker and the wavelet-based interference mitigation algorithm. Hence, the integrated pulse mitigation approach can be employed to provide an enhanced degree of interference detection and suppression.

Deeply Integrated GPS/Low-Cost IMU for Low CNR Signal Processing: Concept Description and In-Flight Demonstration

ABSTRACT: A deeply integrated GPS/low-cost IMU system is developed and applied to re-acquire and track GPS signals with low carrier-to-noise ratio (CNR). The system provides continuous carrier phase tracking without requiring the knowledge of navigation data bits. Flight data with a 90-degree turn are applied to demonstrate re-acquisition and continuous carrier phase tracking of 15 dB-Hz GPS signals.

CATV/ROF transport systems based on one DFB LD with main and side modes injection-locked

A four-wavelength CATV/radio-on-fiber (ROF) transport system based on one distributed feedback laser diode (DFB LD) with main and side modes injection-locked (MSMIL) is proposed and demonstrated. Transmission performances over 100 km of standard single mode fiber (SMF) were investigated. System performances evaluated by carrier-to-noise ratio (CNR), composite second-order (CSO), composite triple beat (CTB), bit error rate (BER), and third order intermodulation distortion to carrier ratio (IMD 3/C) for simultaneous transmission of CATV, local area network (LAN) and intelligent transport system (ITS) signals are improved.

Employing split-band technique and Fabry–Perot etalon filter to improve directly modulated fiber optical CATV system performances

We proposed and demonstrated a directly modulated NTSC 77-channel fiber optical CATV transport system using split-band technique at the transmitting site and Fabry–Perot (FP) etalon filter at the receiving site to improve system performance. Good performance of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained in our proposed systems over a 100-km standard single-mode fiber (SMF) transmission. Employing a FP etalon filter in fiber optical CATV transport systems is useful in real network, as it is simple, passive, and potentially low cost. This proposed system reveals an outstanding one with simpler and more economic advantages than that of externally modulated transport system.

Feasibility Study of ZnO/Ge Bilayer Recording Medium in Blue Laser Recordable Disc

In this paper, a new recording medium (ZnO/Ge bilayer film) used for a write-once blue laser disc is reported. By differential scanning calorimeter technique (DSC), a new endothermic peak of the bilayer was observed at 385 °C. Simultaneously the optical contrast of the ZnO/Ge bilayer film at a wavelength of 405 nm was observed to be higher than 77%. X-ray diffraction (XRD) spectra showed that this film has three major components (ZnO, Zn, and Ge), and an additional component (Zn2GeO4) observed after annealing at 500 °C. From the results of the dynamic tests of the entire disc structure of PC/ZnS–SiO2 (30 nm)/ZnO (13 nm)/Ge (5 nm)/ZnS–SiO2 (20 nm)/Ag (120 nm), the carrier-to-noise ratio (CNR) with a writing power of 10 mW was determined to be 49 dB for a numerical aperture (NA) of 0.65 at a wavelength of 405 nm. In this study, the key to recording in this ZnO/Ge bilayer film was mainly due to the production of Zn2GeO4 between the layers of ZnO and Ge under illumination with the blue laser.

Rewrite Characteristics of a Scattered-Type Superresolution Near-Field Structure Optical Disk with a Ag2O Mask Layer

On the basis of the working mechanism of a silver-oxide-type superresolution near-field structure (super-RENS) disk, we realized excellent rewriting by performing the following steps: (1) initialize the disk at a continuous power of Pi=8.0 mW for 3 s, (2) write at a pulsed power of Pw=8.0–9.0 mW, (3) read (reinitialize only the mask layer) at a superresolution power of Psr=5.5 mW, which lies between the powers under reversible conditions of Pil=4.5 mW and Piu=6.0 mW for the mask layer, (4) erase at a continuous power of Pe=7.5 mW for 3 s, and (4) rewrite at a pulsed power of Pw=8.0–9.0 mW. The carrier-to-noise ratio (CNR) difference between writing and erasing slightly varies for successive rewritings, resulting in CNR=23 dB after 20 rewrite operations for a mark length of 400 nm, which is less than the resolution limit λ/4NA=413 nm. The Ag2O mask layer is decomposed into Ag nanoparticles at 160 °C that aggregate to form nanoclusters dispersed in the mask layer after the initialization operation at Pi=8.0 mW (3 s), and the recording layer made of Ge2Sb2Te5 (GST) is transformed by a second phase transition from a rocksalt crystal structure of fcc to a hexagonal crystal structure (the phase transition temperature range is estimated to be 250–450 °C) at a pulsed power of Pw=8.0–9.0 mW, and vice versa at a continuous power of Pe=7.5 mW for a disk velocity of 2 m/s.

Employing photonic crystal fiber to improve composite second-order and composite triple-beat performances in a two-wavelength wavelength-division-multiplexing transport system

A two-wavelength wavelength-division-multiplexing (WDM) externally modulated transport system employing photonic crystal fiber (PCF) as a dispersion compensation device to compensate the fiber dispersion and to reduce the cross-phase modulation (XPM)–induced cross talk is proposed and demonstrated. In comparison with a two-wavelength WDM externally modulated transport system without a dispersion compensation device or with a conventional dispersion compensating fiber (DCF) as a dispersion compensation device, good performances of composite second-order (CSO) and composite triple beat (CTB) were obtained accompanied by acceptable carrier-to-noise ratio (CNR) in our proposed system.

Diverse Signals Combinations for High-Sensitivity GNSS

Indoor positioning imposes demanding requirements on the design of Global Navigation Satellite System (GNSS) sensors for both the acquisition and tracking functions. Although different combinations of coherent and non-coherent integration periods of a GNSS signal can be used to achieve reliable acquisition of the GNSS signals and indoors positioning, there are limitations to the extent that the integration period of the signal energy can be increased set by the receiver and satellite dynamics and the stability of the local oscillator. Assisting networks for GNSS applications (AGNSS) provide users with the capability of using long integration periods, enabling them to acquire indoor signals at low Carrier to Noise Ratio (CNR) values, where CNR is defined as the ratio of the received signal power over the noise density in units of dB-Hz. In this work we propose and evaluate the potential of a new method that will provide the user with an additional signal energy margin for accurate and reliable indoor positioning, with or without relying on assisted GNSS-type algorithms. The technique proposed here is based on the coherent and non-coherent combination of the energy of signals transmitted from the same GNSS satellite on different frequencies using the multiple open service signals that are to be provided by the Galileo system and under the GPS modernisation. This paper shows the improvement to the receiver acquisition and tracking performance using the proposed technique of combining energies at the L1, L2 and L5 bands for both data and pilot signals.

Simultaneous dispersion and non-linearity compensation with mid-span optical phase conjugation and distributed Raman amplifier for a sub-carrier multiplexed optical transmission link

Optical phase conjugation (OPC) and distributed Raman amplifier (DRA) combination (OPC–DRA) is demonstrated as a potential enabling solution for simultaneous reduction of fiber non-linearities and dispersion compensation of a sub-carrier multiplexed (SCM) optical transmission link. The present work is focused on the use of OPC–DRA combination for system performance improvement in terms of composite second order distortion (CSO) and carrier to noise ratio (CNR) of the SCM link. The analysis further shows that, introduction of DRA with proper pumping scheme significantly reduce fiber non-linearity resulting in improvement of the system performance in terms of CNR, compared to the situation where only mid-way optical phase conjugation is used.

Evaluation methods and requirements for the stimulated Brillouin scattering threshold in a single-mode fiber

This paper presents an experimental discussion of methods for evaluating the input power limitation caused by stimulated Brillouin scattering (SBS) in a single-mode fiber, and known as the SBS threshold. We consider five different evaluation methods including the traditional approach, which considers the input power at which the reflected power is the same as transmitted power. We show that two evaluation methods, which consider the second derivative of the reflected power and the change in the transmitted power characteristics, well describe analogue transmission characteristics by taking account of the input power dependence of the carrier-to-noise ratio (CNR). We also show that the SBS threshold can be evaluated practically by considering a 4% level change in the reflected power against the input power in terms of harmonization with the CNR. We also discuss the evaluation conditions required for an accurate SBS threshold measurement. We clarify the requirements for both the uncertainty in the reflected power and the input power interval in data acquisition.

Capacity Increase in Radial Direction of Super-Resolution Near-Field Structure Read-Only-Memory Disc

We propose a novel super-resolution near-field structure (super-RENS) read-only-memory (ROM) disc with a narrow track pitch using a group tracking technique. The group tracking technique enables the tracking control of an optical disc because it consists of track pitch sizes that are less than the diffraction limit. The group tracking technique to increases capacity in the radial direction of the super-RENS ROM disc. By using this technique, carrier-to-noise ratio (CNR) was obtained at 33 dB and the minimum crosstalk level was -23 dB at the 100 nm pit length. A readout track was selected by controlling the offset level of the tracking error signal in a high definition digital versatile disc (HD-DVD) system. It was confirmed that the capacity of the super-RENS ROM disc with the group tracking structure was improved in the radial direction.

Super-Resolution Recordable Disk with Modified Rhodamine Dye Recording Layer and Contrast Enhanced Layer

A new rhodamine derivative with red light absorption was designed and synthesized. The absorption properties and thermal stability of the rhodamine derivative were discussed. We also studied the characteristics of a super-resolution recordable disk with a modified rhodamine recording layer and a poly(methyl methacrylate) (PMMA) contrast enhanced layer. A sample disk, which consists of a spin-coated rhodamine derivative recording layer and a PMMA contrast enhanced layer, showed excellent recording and readout characteristics with a carrier-to-noise ratio (CNR) of about 43 dB for a mark length of 200 nm (laser wavelength = 635 nm, numerical aperture = 0.60). These results indicate that the rhodamine derivative dye is a promising candidate for optical recording by a super-resolution near-field structure (super-RENS) technique.