The paper studies an all fiber high-speed magneto-optic switch which includes an optical route, a nanosecond pulse generator, and a magnetic field module in order to reduce the switching time of the optical switch in the all optical network. A compact nanosecond pulse generator can be designed based on the special character of the avalanche transistor. The output current pulse of the nanosecond pulse generator is less than 5 ns, while the pulse amplitude is more than 100 V and the pulse width is about 10 to 20 ns, which is able to drive a high-speed magnetic field. A solenoid is used as the magnetic field module, and a bismuth-substituted rare-earth iron garnet single crystal is chosen as the Faraday rotator. By changing the direction of current in the solenoid quickly, the magnetization of the magneto-optic material is reversed, and the optical beam can be rapidly switched. The experimental results indicate that the switching time of the device is about 100 to 400 ns, which can partially meet the demand of the rapid development of the all optical network.
With the rapid development of all-optical network, we bring forward more and more requirements to the performance of
the optical switches. Therefore, a novel magneto-optic switch based on nanosecond pulse is designed and investigated in
this study. It is characterized by no moving parts, high switching speed, and small size etc. The research of magnetooptic
switch mainly involves the design of optical route and nanosecond pulse generator. The optical route designment
includes the selection of magneto-optic crystal, the route designment and performance analysis of polarized light in the
MO switches, as well as the design of magnetic route in Faraday rotator. A bismuth-substituted rare-earth iron garnet
single crystal is chosen as magneto-optic material, and a current solenoid is used to generate the applied magnetic field.
The design of nanosecond pulse generator is based on the avalanche multiplier effect of avalanche transistor. Many kinds
of avalanche transistor are studied in the experiment. The experimental results indicate that the rise time of the output
pulse is about 2-5ns, the pulse width is about 6-20ns, while the pulse amplitude is about 30-150V, thereby it is satisfying
for the magneto-optic switch used in all-optic network. By controlling the magnetization of the magneto-optic material,
the optical beam can be stably switched and the measured switching time is about 100-200ns.
In the paper, a high speed magneto-optic switch based on the Faraday Effect is designed and analyzed. The novel
magneto-optic switch presented in this paper will satisfy high speed transmission and exchange of optical-message
through all-optic network. It consists of three important components as followed novel optical route, Faraday rotator
configuration with ultrafast magnetic field and picosecond impulser. It may switch the optical route by controlling
Faraday rotator which is supplied by picosecond impulser. By the development of the magneto-optic crystal, and
ultrafast magnetic field, the designed magneto-optic switch featured as low insertion loss, low crosstalk, high switching
speed and small bulky size gets ahead of traditional optic switches. As the first part of this paper, a design scheme of
optical route in high speed magneto-optic switch and its experiment analysis will be discussed. Good avalanche effect of
transistor FMMT415 is adopted to generate picosecond pulse signal and then to drive the high speed magnetic field.
Shown by the experiment data, the rising time of the impulse about 1ns, the amplitude of the impulse about 100~500V
are available on the Output end from the picosecond impulser, which can be used as driving current pulse of Faraday
rotator. By using the relationship between the polarization plane rotate direction of polarization light and magnetic
direction, the Faraday rotator is designed.
In this paper two new types of 1x2 all fiber high-speed magneto-optic switches with thick film ferromagnetic bismuth-substituted
rare-earth iron garnets are proposed and tested. Two types of magneto-optic switches are discussed by using
two kinds of crystals. One is the ordinary switch which needs indurance magnetic field to maintain its state; And the
other is latching type switch, the crystal remains in a given magnetic state for unlimited duration without energy supply.
Circuits used to generate magnetic field are also discussed. The theoretical and experimental analysis of optical route,
measurement of switching time and magnetic filed etc. are included. The extinction ratio of the switches are currently
about 20 dB. It can be improved further by additional Faraday rotation created by another magneto-optic (MO) material
in the light path. The switching time of MO material is under 100 ns, it can be ignored. Magnetic field should be able to
change the voltage rapidly in order to obtain fast operating time of the optical switch. The inductance of the solenoid
used for generating the required magnetic field is the bottleneck for rapid switching of the magnetic field in the MO
material. The switching time of the two optical switch are discussed.
The shape and energy distribution of laser beam directly define its applications in laser processing. In order to cater for
different laser processing requirements, the input beam always needs to be transformed. The transformation between the
solid beam and ring beam can be realized by the axicon-based optical devices. A beam transformation optical system,
which uses a pair of positive axicon and negative axicon is designed and analyzed. The novelty of the optical system is
not only that they can focus the laser beam on a ring pattern or solid beam pattern, but also that they can change the
diameter of patter easily by adjusting the separation of the two conical lenses. The optical system is analyzed based on
the geometry optical theory. By adjusting the separation of the convergent conical lens and the divergent conical lens,
different shapes and the energy distributions are gained. At last, a measurement method of the beam profile is introduced
which based on charge coupled device (CCD) The results show that the axicon-based beam transformations raise the
effectiveness of laser and have a wide application prospect in laser processing field.
A novel scheme is proposed to achieve all-optical SPM-based wavelength conversion in a bismuth oxide-based highly
nonlinear photonic crystal fiber. It consists of erbium-doped fiber amplifier, optical circulator, Fiber Fabry-Perot filters,
photonic crystal fiber and fiber Bragg grating. Owing to SPM, a recirculating configuration is designed to induce the
further spectral broadening and wavelength conversion is achieved with a tunable Fiber Fabry-Perot filter. The
simulation results of bismuth oxide-based photonic crystal fiber indicate that the effective index of the fundamental
mode increases monotonically with the increase in the hole pitch, or the decrease in the ratio of the hole diameter to the
hole pitch. The mode effective area steadily increases with the hole pitch. The nonlinear coefficient, which is beneficial
to shorten the fiber length and reduce the required optical power, is expected to be 1100W-1km-1 by using bismuth
oxide-based glass with high nonlinear refractive index and reducing the effective core area with holey microstructure.
The mode-field diameter of bismuth oxide-based is estimated to be 1.98μm and the predicted small effective core area is
3.3μm2. The propagation loss at 1550nm is about 0.8dB/m. The obtained results show that SPM-based PCF-WC has a
potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.
All-optical wavelength conversion plays a major role in providing the wavelength flexibility in optical communication networks. All-optical wavelength converters (AOWCs) based on cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) have attracted considerable research interest. In this paper, we propose a novel scheme for cascaded wavelength conversion based on cross-gain modulation and cross-phase modulation in SOAs. The wavelength conversion operation in the proposed scheme includes two stages, that is, XGM in the first stage followed by the stage of XPM, and thus is expected to have a high ER and a large input power dynamic range simultaneously.
A simple architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is proposed, which consists of an erbium-doped fiber amplifier, a polarization controller, a nonlinear medium
PCF, two tunable fiber Fabry-Perot filters and an optical isolator. Self-phase modulation is utilized to induce spectral
broadening for all-optical wavelength conversion. The desired dispersion properties can be tailored by the parameters of
bismuth oxide-based PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is
expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field
diameter of PCF is estimated to be 1.98μm and the predicted effective core area is 3.3μm2. The intermediate high
numerical aperture fibers between bismuth oxide-based PCF and single-mode fibers are considered to reduce the splicing
loss. The obtained results show that the all-optical wavelength converter has a potential of high conversion efficiency,
wide conversion bandwidth, ultrafast response time, compact configuration and low insertion loss etc.
A novel architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is demonstrated. Self-phase modulation is utilized to induce spectral broadening for the all-optical
wavelength converter. A recirculating configuration is designed to obtain the twice spectral broadening. Therefore,
wavelength conversion is achieved. The design and the simulation of PCF are demonstrated. The desired dispersion
properties can be tailored by the parameters of bismuth oxide (Bi2O3) PCF microstructure. The propagation loss at
1550nm is about 0.8dB/m. The simulation results of PCF indicate the relationship of the effective index of the
fundamental mode, the mode effective area and the holes pitch of PCF. The nonlinear coefficient is expected to be
1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF
is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The design of Bi2O3-based PCF and the
intermediate high numerical aperture fibers between Bi2O3-based PCF and single-mode fibers are considered to reduce
the splicing loss. The obtained results show that the wavelength converter has a potential of wide conversion bandwidth,
high response time, simple configuration and low insertion loss etc.
All-fiber magneto-optic switch is presented in this paper which contains both of optical route and high-speed magnetic
field module. The optical route has a 1×2 Fiber Polarization Beam Splitter (FPBS) and a 2×2 Dual Fiber Polarization
Beam Splitter (DFPBS). The high-speed magnetic field module is core of all-fiber magneto-optic switch which changes
the electronic pulse into magnetic pulse to control the light polarization's plane based on Faraday Effect. The high-speed
magnetic field module adopts Yttrium Iron Garnet (YIG) crystal fiber, nanosecond impulser and high-speed magnetic
field, characterized by no moving parts, low transmission loss and polarization insensitive, low optical insertion loss etc.
YIG crystal fiber, the magneto-optic material with high Verdet constant, used to rotate the polarization plane of the
polarized light 90° in all-fiber magneto-optic switch, is grown by Laser Heated Pedestal Growth (LHPG). CMOS chip
FMMT415 which has good avalanche effect is employed to generate the nanosecond pulse. The pulse we measured is
about 10 ns of the rising time and 0~600V of the amplitude and the output current is used to create the magnetic field.
The obtained results indicate that the switch has a potential of low cross-talk, low insertion-loss and high switching speed.
The optical route will be easily and quickly controlled by the means of nanosecond impulser, therefore, and the
switching time is expected to less than 1 μs.
In this paper, we demonstrated for the first time variable 1.5μm wavelength conversion through cascaded second order
nonlinear processes "SHG+DFG" by fan-out grating in lithium niobate waveguide. We fabricated the waveguide by
annealed proton exchange in periodically poled LiNbO3 (PPLN). The device used in this experiment is 4 cm long, has a
QPM period from 14.8μm to 15.2μm, waveguide width of 12μm, proton exchange depth of 0.7μm, and was annealed for
32h at 350°C. After proton exchange in pure benzoic acid using a SiO2 mask, the substrate was annealed in an oxygen
atmosphere. The wavelength of signal light was set at 1551.3 nm. The wavelengths of tunable pump lights we used in
experiment were 1543.2 and 1556.2 nm, and the corresponding grating periods were 14.87 μm and 15.03 μm,
respectively. The temperature was set at 100.5°C to avoid photo refractive damage and to match the QPM peaks to the
pump wavelengths. The conversion efficiency was about 10dB to be expected with the pump power 175mW in a similar
device with a slightly different QPM period and operated at 125°C.
KEYWORDS: Waveguides, Signal processing, Wavelength division multiplexing, Modulation, Optical amplifiers, Switching, Signal detection, Signal attenuation, Data conversion, L band
In this paper, we proposed a variable operation of a DC-OFS based on double SFG+DFG (Double-SFG+DFG-OFS)
nonlinearity process for the first time. We studied the principle and configuration of three DC-OFS in detail both
theoretically and experimentally. In order to compare with Double-DFG-OFS and Double-SHG+DFG-OFS, we also
used two four-channel-controlling multiple-quasi-phase-matched LiNbO3 wavelength converters and got ten different
outputs spreading across a wavelength range of as broad as 35 nm by changing the combination of two controlling
wavelengths of the two wavelength converters. And one channel signal was converted to shorter and longer wavelength
and the same wavelength by changing the controlling wavelengths. We got higher conversion efficiency compared with
the other two DC-OFSs mentioned above. We used novel M-QPM-LN wavelength converters having a continuously-phase-
modulated domain structure, which can be operated by multiple pump wavelengths with minimum loss of
efficiency. The periods were 14.8μm. The phase of the periodic poling was continuously modulated to satisfy the QPM
condition at four different wavelengths. The frequency spacing of control signal-b is twice as large as the control signal-a.
The operating temperatures were 102.5 and 100.5 C for the first and the second QPM-LN wavelength converters,
respectively.
A novel high-speed magneto-optic (MO) modulator which consists of an integrated wire grid polarizer (WGP), Bi-YIG
waveguide with cladding layer and conducting micro-strip line is proposed. With the integrated WGP, this MO
modulator is faster, more accurate and more stable because it is not only completely driven by electric signals but also
has no mechanically moving parts. Moreover, it is compact-structured and low-cost. Large Faraday rotation is obtained
with specific arrangement of the directions of the bias magnetic field and the modulation RF magnetic field. Optical
route and optic-electrical detect circuit are also designed and analyzed.
All-optical wavelength converters (AOWCs) that utilize nonlinearities in semiconductor optical amplifiers (SOAs) have
attracted considerable research interest. AOWCs based on cross gain modulation (XGM) have a large dynamic range of
the input optical signal power but a low extinction ratio (ER) and a high chirp, whereas AOWCs based on cross phase
modulation (XPM) provide a low chirp and a high ER but suffer from a relative small input power dynamic range. We
point out that there seems to be some complementarity between XGM and XPM. Based on this, we propose a novel
scheme for cascaded wavelength conversion based on cross gain modulation and cross phase modulation in SOAs thus is
expected to have a high ER and a large input power dynamic range simultaneously. The wavelength conversion
operation includes two stages, that is, XGM in the first stage followed by the stage of XPM. In the XGM stage, we use a
band pass filter to increase the frequency response of the SOA. In the XPM, we use the bidirectional input scheme for
MZI to improve the response of XPM and cancel XGM-induced intensity unbalance to get a relative perfect interference.
All-optical wavelength converters (AOWCs) are considered to be important components in future wavelength-division-multiplexed
(WDM) networks. Cross gain modulation schemes in semiconductor optical amplifiers (SOA) are promising
candidates for an all-optical wavelength conversion application due to the simple implementation and effective
conversion. However, the slow gain recovery time of SOA limits the maximum operation speed and causes unwanted
pattern effects. This paper provides a novel scheme for wavelength conversion enables ultra-fast conversion speed. On
the one hand, we utilize a three-wavelength-device (TWD) to reduce the recovery time of the SOA. On the other hand,
we use an optical band pass filter (OBF) which central wavelength is blue shifted with respect to the central wavelength
of the probe beam to increase the frequency response. The combination of a reduction of the SOA recovery time and an
increase of the frequency response enables conversion speed potentially to achieve 160 Gb/s or even faster.
A micro high-speed 1×2 magneto-optic switch, which is used in high-speed all-optical network (AON), is designed and analyzed. The theoretical and experimental analysis of the micro high-speed magneto-optic switch mainly involves the parts of optical route, nanosecond impulser and high-speed magnetic field etc. The study of optical route covers design scheme of polarization optical route in the optical switch, the performance analysis of magneto-optic crystal by using Faraday Effect. The research of nanosecond impulser involves the design, simulation and test of electronic circuit diagram of nanosecond pulse. The analysis of high-speed magnetic field consists of magnetic path design in Faraday rotator and analysis of high-speed magnetic field etc. The nanosecond current pulse transient from nanosecond impulser is used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The experiment results state that nanosecond impulser can output the current pulse with impulse amplitude 10~60V and impulse width 10~ 100ns. The optical beam can be stably switched and the switching time is less than 1μs currently.
A novel type of 2×2 polarization independent magneto-optic switch with low Insertion Loss, nanosecond order switching time is designed and analyzed. The study of the magneto-optic switch involves two main parts: Faraday rotator assembly and optical route design. In faraday rotator design, magneto-optic crystal comparison and selection, two types of Faraday rotator assembly schemes design and analysis; high speed magnetic field simulation and generation; nanosecond trigger signal generator design, simulation and experiment are involved. Within optical router design, a simple but effective optical router with 2×2 mode is introduced. The nanosecond trigger signal supply to the Faraday rotator assembly is 12ns. The key characteristics, insertion loss, far-end crosstalk, switching time of magneto-optic switch that developed at a wavelength of 1550nm have been tested and root causes analyzed.
An all-fiber magneto-optic switch is designed in this paper, which makes use of Faraday Effect, fiber-type polarizing beam splitter/combiner (PBS/PBC), magneto-optic crystal fiber, nanosecond impulser and high-speed magnetic field control technology. The design scheme uses magneto-optic crystal fiber instead of bulky magneto-optic crystal. The optical route design includes linear layout of magneto-optic crystal fiber, the optical route design of polarized light in fiber PBS/PBC, magnetic route design and analysis of linear solenoid, etc. A solenoid which is driven by nanosecond current and can generate high-speed magnetic field is designed and manufactured. The result analysis shows that pulse signal can be greatly strengthened by impressed-bias static magnetic field which is perpendicular to transmission direction of light beam. Static magnetic field insures the intensity of induced magnetization where the light passes come back to original value, so that it can offer high-extent magnetization equality. The intensity of magnetic field can be improved to two orders when the length ratio of magneto-optic crystal fiber to solenoid is increased eight times. When the diameter of magneto-optic crystal and solenoid is decreased from three millimeters to one millimeter, the intensity of magnetic field can be improved to one order. The all fiber magneto-optic switch is slim in structure, flexible, easy to high-density integration and expansion, so there are many integration methods to design all-fiber magneto-optic switch array, which is characterized of smaller bulk, higher magnetic field usage, lower consumption and driving voltage, etc.
In the paper, a high speed magneto-optic switch based on the Faraday Effect is designed and analyzed. The optic switch adopts Faraday rotator, nanosecond impulser, and high speed magnetic field, so it is characterized by no moving parts, low transmission loss and polarization insensitive, low optical insertion loss etc. Using the polarization and Faraday Effect of magneto-optic crystal, the magneto-optic switch can hold the function of all-optical switching, which is needed in all-optical communication networks. As the first part of this paper, a design scheme of optical route in high speed magneto-optic switch and its experiment analysis will be discussed. Good avalanche effect of transistor 2N5551 is adopted to generate nanosecond pulse signal and then to drive the high speed magnetic field. Shown by the experiment data, the rising time of the impulse about 10ns, the amplitude of the impulse about 10~60V are available on the Output end from the nanosecond impulser, which can be used as driving current pulse of Faraday rotator. By using the relationship between the polarization plane rotate direction of polarization light and magnetic direction, the Faraday rotator is designed. It's unique double magnetic field and externally applied static magnetic design can greatly speed the excitation time of the internal inductive magnetic field and shorten the switching time of magneto-optic switch.
Magneto-optic switch has been widely researched due to its capabilities handling large beam cross sections, operating at low voltages, featured as low insertion loss and intrinsic non-reciprocity. However, the switching speed is rather slow: switching time of available magneto-optics switches are of hundreds microseconds. Previously, we developed a novel type high speed magneto-optic switch based on Faraday rotation effect of light in yttrium-iron-garnet (YIG). The switch shows its good performance and high reliabilities. However, it had some disadvantages: 1) Although it was polarization independently designed for the insertion loss, some dependence about 0.5dB was observed due to the components' misalignments since it has many components and adjustment points; 2) Faraday rotator assembly designed by using double YIG rods with diameter 3 mm require much higher switching current to rotate the light by 90°. And the heat generated when operating may also affect the YIG performance. 3) The narrow and sharp pulse width of nanosecond trigger impulse signal generated with short duration can't accumulate the high speed switching magnetic field large enough to drive the YIG reach saturation magnetic field within a trigger period. In this paper, we mainly devote to design an improved switch featured as compact optical route, much more effective Faraday rotator assembly and nanosecond trigger impulse signal with wider pulse width.
A novel micro high-speed 2x2 magneto-optic switch and its optical route, which is used in high-speed all-optical communication network, is designed and analyzed in this paper. The study of micro high-speed magneto-optic switch mainly involves the optical route and high-speed control technique design. The optical route design covers optical route design of polarization in optical switch, the performance analysis and material selection of magneto-optic crystal and magnetic path design in Faraday rotator. The research of high-speed control technique involves the study of nanosecond pulse generator, high-speed magnetic field and its control technique etc. High-speed current transients from nanosecond pulse generator are used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The optical route design schemes and electronic circuits of high-speed control technique are both simulated on computer and test by the experiments respectively. The experiment results state that the nanosecond pulse generator can output the pulse with rising edge time 3~35ns, voltage amplitude 10~90V and pulse width 10~100ns. Under the control of CPU singlechip, the optical beam can be stably switched and the switching time is less than 1μs currently.
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