In this paper, a simple and effective tunable multi-wavelength ytterbium-doped fiber laser (MWYDFL) is proposed and demonstrated. A nonlinear polarization rotation (NPR) structure, including polarization controller (PC) and polarizationdependent isolator (PDI) is used as the wavelength selector and works to generate intensity-dependence transmission to suppress the mode competition and solves the problem of greater intensity of side modes. Thus the stable all-fiber ring cavity structure is realized. Through controlling and adjusting the polarization of the PC in the cavity, a multiwavelength and tunable single wavelength laser with good performance is achieved under the room temperature. The laser outputs of the single-wavelength can be tuned about 12 nm with an interval of about 1 nm from 1074.42 nm to 1090.97 nm. The side-mode suppression ratios (SMSRs) and the linewidths of these lasing lines are all over 50 dB and less than 0.02 nm. Single-wavelength, dual-wavelength, triple-wavelength and quadruple-wavelength can be switched by appropriately adjusting the PC. The power fluctuations and wavelength shifts are less than 2 dB and 0.02 nm in an hour at room temperature.
A simple and effective tunable and switchable L-band multi-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. A Mach-Zehnder interferometer with a fiber Bragg grating inside one arm used as the wavelength selective filter makes the output wavelength at the L band. The nonlinear polarization rotation effect induced by a 5-km long single mode fiber, a polarization controller (PC) and polarization-dependent isolator is used to effectively suppress the mode competition. Thus the stable all-fiber ring cavity structure with multi-function operation is realized. The laser outputs of the single-wavelength can be tuned about 12 nm with an interval of 1 nm in L band. The side-mode suppression ratios (SMSRs) of these lasing lines are all over 60 dB. And single-wavelength, dual-wavelength, triple-wavelength and quadruple-wavelength can be switched by appropriately adjusting the PC. The SMSRs of multiwavelength lasing lines are all over 50 dB. The laser has the advantages of simple all-fiber configuration, low cost, high stability and operating at room temperature.
KEYWORDS: Modulation, Single sideband modulation, Radio over Fiber, Microwave radiation, Modulators, Signal detection, Eye, Single mode fibers, Phase shifts, Particle filters
To simultaneously modulate and transmit 10-Gb/s baseband and 20-GHz microwave signals on a single wavelength
using single-sideband (SSB) modulation technique, a novel ROF scheme is proposed and verified by simulation. Based
on a Dual-Parallel Mach-Zehnder Modulator (DPMZM) the scheme can carry the microwave signal on the upper
sideband(USB) and the baseband signal on the lower sideband(LSB). It is to be seen from the simulated results that the
crosstalk between the signals with dual services is very small. By means of subcarrier-multiplexing (SCM) technique, the
optical 20-GHz microwave wave carrier is generated to carry 155-Mb/s baseband signal and 10-Gb/s baseband signal is
imposed on the original optical carrier via SSB modulation. The simulated results of BER and the eye diagram are
achieved separately. The signals with dual services are successfully transmitted over 50-km single-mode fiber.
Simultaneous generation and transmission of 10-Gb/s baseband signal and 20-GHz microwave signal with 155-Mb/s
on-off-keying (OOK) data on a single wavelength over 50-km-long fiber link based on a dual-parallel Mach-Zehnder
modulator (DPMZM) are investigated. After simultaneous modulation of the baseband signal and microwave signal at
central office (CO), the hybrid signals are separated by interleaver(IL) or fiber Bragg grating (FBG) at base station (BS).
The center wavelength spacing and bandwidth of IL, also the reflection ratio, center wavelength and bandwidth of FBG
are to be considered carefully as the baseband and microwave signal are only tens of GHz spacing and hard to be
separated with each other. Through theoretical analyses and simulation, for the demonstrated hybrid transmission system,
the relations of Q factor with the reflection ratio and bandwidth of FBG are analyzed separately in different fiber links
(SMF and DSF).
Acousto-optic tunable filter (AOTF) is one of important optical switch components in optical networks. The possibility of tellurium dioxide acousto-optic tunable filter (TeO2 AOTF) as an optical add/drop multiplexer (OADM) is studied on the basis of the theory of the anomalous acousto-optic Bragg diffraction and the design principle of non-collinear AOTF. Its main performances and structure are analyzed and discussed, and the significance of incident angles and interaction lengths for its performances is presented. The model for optimization design is built under some limitation and the transducer areas is adopted as a regulator for performance, the designed example of the TeO2 AOTF for WDM systems is given by the optimized method.
In the paper, a weighted-coupling scheme of a SiO2 film-loaded Ti:LiNbO3 quasi-collinear integrated acousto-optic mode converter is reported, in which an angular offset between the acoustic and optical waveguides is introduced to implement an optimized Hamming weighted function for realization of ultralow sidelobe level. Acoustic wave guiding properties have been investigated for films such as SiO2, ZnO on LiNbO3 firstly. SiO2 film on LiNbO3 was selected as acoustic waveguide. With the mode analysis of the acoustic wave guide and the theory of coupling mode the limit of the width, weighted coupling coefficient and the characteristics of the conversion of acousto-optic modes are obtained. As the angle between acoustical and optical waveguides is 0.45°, the worst sidelobe level is -16dB and the theoretical values of bandwidths of -3dB and -10dB is 1.37nm and 2.31nm respectively, which have excelled the domestic reported level.
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