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 this paper, an all fiber high-speed magneto-optic switch based on Faraday rotation in Bismuth-substituted Rare-earth
Iron Garnet single crystal is proposed and investigated. It contains optical route, picosecond pulse generator and
high-speed magnetic field structure. The optical route is designed with the function of switching the output optical
signals in the networks. The biasing circuit for the magnetic field should be able to change the voltage rapidly in order to
obtain fast operating time of the magneto-optic switch. Therefore, a kind of picosecond pulse generator based on the
low-voltage avalanche characteristics of RF-BJT BFP450 is designed to drive a high-speed magnetic field. The
experimental results indicate that the rise time of the output current pulse is only hundreds of picoseconds, which is
satisfying for the high-speed magneto-optic switch. A current solenoid is used as high-speed magnetic field structure in
this paper. It is noted that there is a time constant associated with the inductance of the current solenoid, which is an
important factor determining the switching time. The switching time of the device also depends on the switching of the
magnetic domains in the magneto-optic material. By controlling the magnetization of the magneto-optic material, the
optical beam can be stably switched. The measured switching time of the device is only 134.2ns, so it can be widely used
in the all-optical communication networks.
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.