Injection Power Level Research Articles

Photobleaching Effect on the Radiation‐Induced Attenuation of an Ultralow Loss Optical Fiber at Telecommunication Wavelengths

An unexpected high sensitivity to radiation has recently been discovered in a new generation of ultralow loss pure‐silica core optical fiber, the Corning Vascade EX1000. It is investigated how the injected power level of the probing signal at 1310 and 1550 nm affects the radiation‐induced attenuation (RIA) during and after steady‐state X‐ray exposure up to a total ionizing dose (TID) of 250 kGy (SiO2) at room temperature. The experiments confirm this fiber's high sensitivity to radiations, mainly due to the generation of metastable defects absorbing in the infrared domain. RIA kinetics are characterized by a non‐monotonic behavior, reaching a maximum of the radiation‐induced losses at 3.3 kGy (SiO2). Through successive radiation tests, the RIA dependence on the signal power level at the dose corresponding to the maximum of the RIA is studied, finding out that, for the two investigated wavelengths, the RIA follows a power law dependence in the 100 nW–1 mW injected power range, whose exponent seems independent on the dose rate (between 1 and 6 Gy s−1). The results highlight a clear photobleaching phenomenon, with the RIA associated to these metastable defects strongly reduced at higher injected powers of mW levels.

Photobleaching Effect on Infrared Radiation-Induced Attenuation of Germanosilicate Optical Fibers at MGy Dose Levels

We investigated the radiation-induced attenuation (RIA) at 1550 nm under X-rays in two single-mode germanosilicate optical fibers (OFs): the Corning SMF-28e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and a homemade fiber manufactured by the Université Côte d'Azur in the framework of the CERTYF project. The RIA dependence on the injected power level of the probing signal is studied in order to analyze the photobleaching phenomenon at high doses [>100 kGy(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )]. The Corning SMF-28e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> revealed no RIA variation with the signal power (microwatts-milliwatts range), proving to be a good candidate for distributed OF sensor (DOFS) applications, while the CERTYF OF showed a clear photobleaching effect. A fitting routine based on the second-order growth kinetics model of Griscom has been performed, which has shown good consistency with the experimental results and offered a quantitative evaluation of the photobleaching effect on the CERTYF OF.

A Multi-Mode Multi-Coil Coupled Tuned Inductive Peaking ILFD for Low Injected Power With Compact Size

In this paper, a multi-mode magnetically coupled and tuned inductive peaking technique with impedance transforming capability is proposed to achieve a wider operational locking range in the injection locked frequency divider (ILFD) for low injected power levels. Fabricated in 65 nm CMOS process, the proposed ILFD operating at 60 GHz, achieves a locking range of 16.3% from 53.2 to 63 GHz with a low injected power of -10 dBm. Occupying a small area of 0.0288 mm2, the ILFD delivers an average single-ended output power of -6 dBm with a dc power consumption of 3.7 mW from a 1.2 V supply voltage. The power efficiency (P out /P dc ) of the proposed ILFD is 6.8%.

Experiment on Ka‐band amplifiers degraded and damaged by electromagnetic waves

Research on amplifiers injected by high-power microwave is important and lays foundation for reinforce technology. This study reports an experiment on Ka-band amplifiers injected and damaged by electromagnetic waves. The continuous wave and the pulse wave are injected into the amplifiers which are based on HMMC5040 chips. The injected power level increases until the amplifiers are damaged. The results are recorded and analysed. The results show that: (i) the uncharged amplifiers need more injected power to be damaged compared with the charged amplifiers. (ii) To degrade or damage the amplifiers, the pulse wave need more power. (iii) The first node of the HMMC5040 chip is damaged in the experiment, so this is the key part for anti-radiation design.

Linewidth Enhancement Factor and Amplification of Angle-Modulated Optical Signals in Injection-Locked Quantum Cascade Lasers

AbstractThis paper presents a nonlinear analysis of the effect of linewidth enhancement factor (LEF) on the amplification of angle-modulated optical signals in injection-locked mid-infrared (IR) quantum cascade lasers (QCLs). A higher value of LEF tends to conserve the output angle modulation index of the amplified mid-IR signal particularly in the low-modulation frequency region. Further, a higher value of signal injection ratio produces a wider bandwidth of the locked QCL amplifier. The LEF introduces asymmetry in the lockband (LB) of the injection-locked QCL and this asymmetry increases with the increase in the value of LEF. Typically ratio of calculated lower-side LB to upper-side LB for an injection power level of – 20 dB and a LEF of unity is 1.67. The electron relaxation time in the uppermost subband lasing level in a three-level system has a profound effect on the LB asymmetry in a QCL.

Examination of the entry to burn and burn control for the ITER 15 MA baseline and hybrid scenarios

The entry to burn and flattop burn control in ITER will be a critical need from the first DT experiments. Simulations are used to address time-dependent behaviour under a range of possible conditions that include injected power level, impurity content (W, Ar, Be), density evolution, H-mode regimes, controlled parameter (Wth, Pnet, Pfusion), and actuator (Paux, fuelling, fAr), with a range of transport models. A number of physics issues at the L–H transition require better understanding to project to ITER, however, simulations indicate viable control with sufficient auxiliary power (up to 73 MW), while lower powers become marginal (as low as 43 MW).

Ring Oscillator Based Injection Locked Frequency Divider Using Dual Injection Paths

Ring oscillator based injection locked frequency dividers (ILFD) generally feature higher power efficiency compared to conventional static frequency dividers. However it is difficult for ring oscillator based ILFDs to achieve large division ratio and wide input locking range at the same time. To increase the input locking range, a ring oscillator based ILFD utilizing dual injection technique is proposed in this letter. For this, both tail injection and direct injection are applied in phase such that the output currents of the two mixing processes corresponding to the two injection paths are added constructively at the output frequency $\omega o$ and the overall injection efficiency is therefore increased. A differential buffer circuit with dual injection is proposed. Equivalent circuit modeling of the dual injection buffer and mathematical analysis of locking range enhancement are presented. The core ring oscillator consists of 4 stages of the dual injection buffers. It is fabricated in a 65 nm CMOS technology and consumes less than 2 mW with supply voltage of 1.2 V. Its locking range is from 1.2 to 20.7 GHz without any tuning at 0 dBm injection power level. The proposed ILFD is compact with the core only occupying 15 $\mu$ m $\,\times\,$ 30 $\mu$ m and does not need any extra controls, making it suitable for integrated wideband phase locked loop.

Predictive Simulations of Plasma Heating and Current Drive by Neutral Beam Injection on EAST

Long pulse and high performance steady-state operation is the main scientific mission of experimental advanced superconducting tokamak (EAST). In order to achieve this objective, high-power auxiliary heating systems are essential. Radio frequency (RF) wave heating and neutral beam injection (NBI) are two principal methods. NBI is an effective method of plasma heating and current drive, and it has been used in many magnetic confinement fusion devices. Based on the plasma equilibrium of EAST (Li et al., Plasma Phys Control Fusion 55:125008, 2013) plus previous EAST experimental data used as initial conditions, the NBI module (Polevoi et al., JAERI-Data, 1997) employed in automated system for transport analysis (ASTRA) code (Pereverzev et al., IPP-Report, 2002) is applied to predict the effects of plasma heating and current drive with different neutral beam injection power levels. At certain levels of plasma densities and plasma current densities, the simulation results show that the NBI heats plasma effectively, also increases the proportions of NB current and bootstrap current among total current significantly.

Coupled Dual LC Tanks Based ILFD With Low Injection Power and Compact Size

This letter presents a fully differential injection locked frequency divider using coupled dual LC tanks. The proposed injection locked frequency divide-by-2 divider achieves a wide locking range with low injected power levels. The divider, fabricated in 0.18 μm SiGe BiCMOS process achieves a locking range of 3.77 GHz with an injected power as low as -16 dBm, a phase noise of -116 dBc/Hz at 10 kHz offset with an input referred phase noise of -109.7 dBc/Hz at 10 kHz offset at 25 GHz, maximum output power of -2.44 dBm, efficiency of 18.5% and the dc power consumption is 4.8 mW.

A low-power differential injection-locked frequency divider with output power flatness in 0.5 μm E/D-mode GaAs PHEMT

This study implemented an injection-locked frequency divider (ILFD) on Ka-band millimeter-wave communication systems in 0.5μm enhancement/depletion-mode (E/D-mode) GaAs PHEMT technology. The ILFD presents a low-power design based on the differential-injection circuit topology without using any injectors. Compared with the conventional single-injection ILFD circuits, the proposed ILFD exhibits output power flatness and wide locking range characteristics with a power consumption of 0.9mW under a 0.4V supply. The self-oscillation frequency was chosen to be 20GHz for divided-by-2 operation. The measured locking range is approximately 11.5GHz ranging from 32.5GHz to 44GHz when the injection power level is 5dBm. The locking range exhibiting a 3dB power roll-off characteristic at output is 10.5GHz ranging from 33GHz to 42.5GHz.

Microwave Stabilization of a HEB Mixer in a Pulse-Tube Cryocooler

We report the results of our study of the stability of an 800 GHz hot electron bolometer (HEB) mixer cooled with a pulse-tube cryocooler. Pulse-tube cryocoolers introduce temperature fluctuations as well as mechanical vibrations at a frequency of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex></formula> 1 Hz, both of which can cause receiver gain fluctuations at that frequency. In our system, the motor of the cryocooler was separated from the cryostat to minimize mechanical vibrations, leaving thermal effects as the dominant source of the receiver gain fluctuations. We measured root mean square temperature variations of the 4 K stage of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\sim$</tex></formula> 7 mK. The HEB mixer was pumped by a solid state local oscillator at 810 GHz. The root mean square current fluctuations at the low noise operating point (1.50 mV, 56.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $\mu\hbox{A}$</tex></formula> ) were <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim 0.12\ \mu\hbox{A}$</tex></formula> , and were predominantly due to thermal fluctuations. To stabilize the bias current, microwave radiation was injected to the HEB mixer. The injected power level was set by a proportional-integral-derivative controller, which completely compensates for the bias current oscillations induced by the pulse-tube cryocooler. Significant improvement in the Allan variance of the receiver output power was obtained, and an Allan time of 5 s was measured.

A Millimeter-Wave Low-Power Active Backscatter Tag for FMCW Radar Systems

In this paper, a fully integrated active backscatter transponder based on the switched injection-locked oscillator (SILO) principle for frequency-modulated continuous-wave radar applications is presented. Furthermore, a method to characterize a SILO amplifier is extended and utilized to measure the system parameters of the presented backscatter tag that operates at 34.45 GHz. It is digitally tunable from 32.7 to 35.4 GHz and reaches an unpulsed output power of 5 dBm. Above injection power levels of $-\hbox{53 dBm}$ , the SILO tag responds phase coherent at its maximum output power. In system measurements, the SILO backscatter transponder was used to perform distance measurements at ranges from 0.7 to 11.5 m. A remarkably good mean distance measurement error of 7 cm with a standard deviation of 10 cm was achieved in a strong multipath environment. The single measurement precision is below 3 mm.

Combined Self-Seeding and Carrier Remodulation Scheme for WDM-PON

In this work, we propose a novel self-seeded WDM-PON topology. Unlike previous works, in our case, the self-seeding occurs in RSOAs located at the OLT, allowing upstream transmission based on carrier remodulation at the ONT. Thus, a single wavelength per user can be employed for both traffic directions while eliminating the need for an external broadband light source at the CO. A maximum bidirectional 2.5 dB power penalty for a BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> was obtained for an injection power level of -22 dBm into the ONT RSOAs. We also investigate the tolerance of downstream BER to downstream extinction ratio (ER <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> ) and self-seeding power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> ), as well as analyze the impact of upstream extinction level (ER <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">UP</sub> ), injection power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> ) and ER <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> levels on upstream BER performance, on symmetric 1.25 Gbps OOK transmission over 20 km without DTLA and FFCI mechanisms. We have successfully demonstrated downstream error free transmission (BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) for an as low as 3.5 dB.

Reconfigurable photonic ultrawideband pulse generation from an optically injected semiconductor laser

We demonstrate reconfigurable photonic ultrawideband (UWB) pulse generation by injecting a phase-modulated optical wave into a semiconductor laser. By adjusting the injection power level and phase modulation depth, the photonic UWB generator is capable of generating either a single-optical-carrier monocycle or power-efficient UWB pulses. A UWB pulse with spectral power efficiency (SPE) of 36.10% has been achieved by optimizing the injection parameters. Transmission in an 8.4 km single mode fiber results in a degradation of SPE to 27.55% without significant pulse distortion.

Role of Suppressed Mode in the Polarization Switching Characteristics of Optically Injected VCSELs

Polarization switching characteristics of birefringent vertical cavity surface emitting lasers (VCSELs) subject to polarized optical injection are investigated experimentally. The role of the suppressed mode of VCSELs in reducing the injected optical power required for polarization switching (PS) has been identified. For orthogonal optical injection, the minimum optical injection power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> ) to induce PS is found to occur at a frequency detuning (FD) of -11 GHz corresponding to the VCSEL birefringence. The value of the minimum P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inj</sub> reduced significantly with increasing bias current. The FD for PS is independent of the VCSEL bias current, injected power level, and a defined range of polarization angles of the injected light. However, for parallel optical injection, the minimum FD for PS is normally found to be positive and dependent on the VCSEL bias current and injected optical power.

Fiber optical CATV transport systems based on PM and light injection-locked DFB LD as a duplex transceiver

A bidirectional fiber optical CATV transport system employing phase modulation (PM) scheme and frequency up-conversion technique to deal with downstream CATV signals, and using light injection-locked distributed feedback laser diode (DFB LD) as a duplex transceiver at the receiving site is proposed and experimentally demonstrated. With optimum injection wavelength and power level, a DFB LD is efficiently employed for both the transmitter and receiver operations. Such DFB LD is used to replace the functions of delay interferometer (DI) and CATV receiver, and also to be as the upstream light source. To the best of our knowledge, it is the first time to successfully utilize a DFB LD to detect the phase-modulated CATV signals. Impressive experimental results prove that our proposed systems not only can employ the PM scheme and the frequency up-conversion technique to optimize the overall performances of systems, but also can use an injection-locked DFB LD to detect the downstream phase-modulated CATV signals as well as to transmit the upstream CATV ones simultaneously.

Modeling the Dynamic Response of an Optically-Injected Nanostructure Diode Laser

We reformulate a dimensionless approach to evaluate the operational dynamics of an optically injected nanostructure laser as a function of the injection strength and the detuning frequency to account for the large nonlinear gain component associated with nanostructure lasers through the nonlinear carrier relaxation rate and gain compression coefficient. The large nonlinear carrier relaxation rate and gain compression coefficient are shown to impact the level of stability numerically predicted in the optically injected laser at low injected power levels. The numerical model is verified experimentally by optically injecting a quantum-dash Fabry-Perot laser with an operating wavelength of approximately 1550 nm. The quantum-dash laser's large damping rate, gain compression coefficient, and sufficiently small linewidth enhancement factor are observed to inhibit period-doubling and chaotic operation under zero frequency-detuning conditions. The inclusion of the nonlinear carrier relaxation rate in the simulation is shown to greatly enhance the agreement between the numerical predictions and the experimentally observed dynamics.

Differential Monitoring of AWG-Filtered Reflection Signal for Accurate Transmitter Power Control of Injection-Locked WDM PON Systems

We propose a simple and robust, automatic power control architecture for the injection-locked, wavelength-division-multiplexed passive optical network system. Monitoring the differential of reflected signal power from the mid-stage fiber mirror placed after the arrayed waveguide grating in the central office, the problem of transmitted signal power fluctuation experienced in conventional, back-facet photodiode monitoring schemes is eliminated. Results show the excellent control of the transmitted power within a peak-to-peak fluctuation of 0.1 dB over a wide operating range of temperature and injection power level.

Dynamic Switching Response of Semiconductor Ring Lasers to NRZ and RZ Injection Signals

Dynamic response of semiconductor ring lasers (SRLs) to external optical injection with nonreturn-to-zero (NRZ) and return-to-zero (RZ) waveforms is investigated using a model including linear and nonlinear mode coupling. The switching characteristics are simulated under various device sizes, injection power levels, and frequency detuning. For NRZ, the switching time reduces with decreasing SRL radius, which has a reasonable agreement with the current experimental results. It is also demonstrated that RZ pulse with duration of several picoseconds can reliably switch 6-mum radius SRL over a detuning range of more than 100 GHz, with the end state self-sustained after switching.

A Direct Power Injection Model for Immunity Prediction in Integrated Circuits

This paper introduces a complete simulation model of a direct power injection (DPI) setup, used to measure the immunity of integrated circuits to conducted continuous-wave interference. This model encompasses the whole measurement setup itself as well as the integrated circuit under test and its environment (printed circuit board, power supply). Furthermore, power losses are theoretically computed, and the most significant ones are included in the model. Therefore, the injected power level causing a malfunction of an integrated circuit, according to a given criterion, can be identified and predicted at any frequency up to 1 GHz. In addition to that, the relationship between immunity and impedance is illustrated. Simulation results obtained from the model are compared with measurement results, and these demonstrate the validity of this approach.