In this paper, dual-wavelength laser emission of an erbium-doped fiber laser (EDFL) with a tunabl... more In this paper, dual-wavelength laser emission of an erbium-doped fiber laser (EDFL) with a tunable distinct wavelength selection of the simultaneously produced laser lines was achieved by applying a parallel comb filter configuration based on the optical Vernier effect. The intracavity inserted proposed comb filter consists of two parallel branches to generate the Vernier effect. Each branch is an in-line Mach–Zehnder interferometer (MZI) filter, which is composed of a polarization-maintaining fiber fusion spliced between single-mode fibers with sphere shapes at both ends. The tunability of the selected laser wavelength was realized by submerging the proposed filter in different sodium chloride/water mixtures. The proposed comb filter-based Vernier effect was used to independently achieve the selection of the dual-wavelength EDFL lines and for refractive index (RI) sensing applications. The in-line MZI1 and MZI2 structures show a wavelength shift sensitivity to RI variations of −88 and 79 nm/RIU, respectively. Our proposed MZI structure presents a reliable, straightforward, and low-cost spectral comb filter for separate tunable dual-wavelength laser generation in the c-band region. Furthermore, the proposed filter structure-based Vernier effect presents a new perspective and method in the RI sensing application.
This book takes a solid step toward a systematic analysis of the implications of microfinance for... more This book takes a solid step toward a systematic analysis of the implications of microfinance for the role and regulation of capital markets. The authors address integration of capital markets with microfinance, technological innovations such as the use of mobile phone technology, the consequences of women’s access to micro-loan borrowings, and the regulatory challenges and opportunities emerging as the landscape of microfinance dramatically evolves.
In this paper we consider Millimeter wave (mmWave) Massive MIMO systems where a large antenna arr... more In this paper we consider Millimeter wave (mmWave) Massive MIMO systems where a large antenna array at the base station (BS) serves a few scheduled terminals. The high dimensional null space of the channel matrix to the scheduled terminals is utilized to broadcast system information to the non-scheduled terminals on the same time-frequency resource. Our analysis reveals the interesting result that with a sufficiently large antenna array this non-orthogonal broadcast strategy requires significantly less total transmit power when compared to the traditional orthogonal strategy where a fraction of the total resource is reserved for broadcast of system information.
We consider a point-to-point mm-wave massive multiple-input multiple-output hybrid beamforming sy... more We consider a point-to-point mm-wave massive multiple-input multiple-output hybrid beamforming system where the transmitter is impaired with in-phase and quadrature-phase imbalance (IQI). We propose a novel channel estimation and IQI parameter estimation algorithm which first estimates the true sparse channel parameters using which it then estimates the IQI parameters. We show that the transmitter IQI limits the spectral efficiency of hybrid beamforming systems at high signal-to-noise ratio irrespective of the choice of hybrid precoder/combiner. We also propose a novel IQI symbol-level pre-compensation scheme at the transmitter which modifies the input symbol vector to the transmit radio frequency (RF) chains in such a way that the symbol vector received at the output of the RF chains is free from any IQI. Analysis and simulations confirm the effectiveness of the proposed IQI pre-compensation technique.
In this paper, dual-wavelength laser emission of an erbium-doped fiber laser (EDFL) with a tunabl... more In this paper, dual-wavelength laser emission of an erbium-doped fiber laser (EDFL) with a tunable distinct wavelength selection of the simultaneously produced laser lines was achieved by applying a parallel comb filter configuration based on the optical Vernier effect. The intracavity inserted proposed comb filter consists of two parallel branches to generate the Vernier effect. Each branch is an in-line Mach–Zehnder interferometer (MZI) filter, which is composed of a polarization-maintaining fiber fusion spliced between single-mode fibers with sphere shapes at both ends. The tunability of the selected laser wavelength was realized by submerging the proposed filter in different sodium chloride/water mixtures. The proposed comb filter-based Vernier effect was used to independently achieve the selection of the dual-wavelength EDFL lines and for refractive index (RI) sensing applications. The in-line MZI1 and MZI2 structures show a wavelength shift sensitivity to RI variations of −88 and 79 nm/RIU, respectively. Our proposed MZI structure presents a reliable, straightforward, and low-cost spectral comb filter for separate tunable dual-wavelength laser generation in the c-band region. Furthermore, the proposed filter structure-based Vernier effect presents a new perspective and method in the RI sensing application.
This book takes a solid step toward a systematic analysis of the implications of microfinance for... more This book takes a solid step toward a systematic analysis of the implications of microfinance for the role and regulation of capital markets. The authors address integration of capital markets with microfinance, technological innovations such as the use of mobile phone technology, the consequences of women’s access to micro-loan borrowings, and the regulatory challenges and opportunities emerging as the landscape of microfinance dramatically evolves.
In this paper we consider Millimeter wave (mmWave) Massive MIMO systems where a large antenna arr... more In this paper we consider Millimeter wave (mmWave) Massive MIMO systems where a large antenna array at the base station (BS) serves a few scheduled terminals. The high dimensional null space of the channel matrix to the scheduled terminals is utilized to broadcast system information to the non-scheduled terminals on the same time-frequency resource. Our analysis reveals the interesting result that with a sufficiently large antenna array this non-orthogonal broadcast strategy requires significantly less total transmit power when compared to the traditional orthogonal strategy where a fraction of the total resource is reserved for broadcast of system information.
We consider a point-to-point mm-wave massive multiple-input multiple-output hybrid beamforming sy... more We consider a point-to-point mm-wave massive multiple-input multiple-output hybrid beamforming system where the transmitter is impaired with in-phase and quadrature-phase imbalance (IQI). We propose a novel channel estimation and IQI parameter estimation algorithm which first estimates the true sparse channel parameters using which it then estimates the IQI parameters. We show that the transmitter IQI limits the spectral efficiency of hybrid beamforming systems at high signal-to-noise ratio irrespective of the choice of hybrid precoder/combiner. We also propose a novel IQI symbol-level pre-compensation scheme at the transmitter which modifies the input symbol vector to the transmit radio frequency (RF) chains in such a way that the symbol vector received at the output of the RF chains is free from any IQI. Analysis and simulations confirm the effectiveness of the proposed IQI pre-compensation technique.
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