As an application in the backlight system of small LCD display, we realized a pure white light source by mixing red, green, blue (RGB) lights using a 3 X 3 Hard Plastic Cladding Fiber (HPCF) coupler. We also proposed the 0.44 inch LED backlight system with these fiber-optic pure white sources and characterized its illumination characteristics.
Using optimized fusion-tapering technique, we fabricated HPCF coupler which combines three input lights over the circularly formed waist. HPCF has the core diameter of 200 μm and clad diameter of 230 μm. The fabricated 3 X 3 HPCF coupler has the perfect uniformity of about 0.3 dB, low insertion loss of 5.5 dB, and low excess loss of 0.8 dB, which shows excellent uniform power splitting ratio.
In order to improve the transmission performance, The RGB chip LEDs were butt-coupled directly to the ferruled input ports of the coupler and packaged by TO46-can type. In the produced white color by HPCF coupler, the photometric brightness at the circular endface of outputs of HPCF coupler was in a rage of 10062 ~ 10094 cd/m<sup>2</sup>.
The fiber optic white color combiner provides tunable white sources excluding heat source and having thickness of 200 μm. We also proposed a 0.44 inch LED backlight system with these fiber-optic pure white sources. With the proposed device, we obtain the improved uniformity in luminance distribution and wide color gamut by using the white light mixing red, green and blue lights.
A Q-switched all-fiber laser application based on a novel micro-optical waveguide (MOW) on micro-actuating platform (MAP) light modulator is presented. A fused biconical taper (FBT) coupler acts as MOW, mounted on an electromechanical system, MAP, where an axial stress over the waist of FBT coupler is precisely controlled. The axial stress induced refractive index changes caused the coupling efficiency to result in modulation of optical power. The light modulator was implemented in a laser cavity as a Q-switching element. Q-switching of Yb<sup>3+</sup>-doped fiber laser was successfully achieved with the peak power of 192mW at 4.1W pump power and 699mW at 5.2W at the repetition rate of 18.6kHz. Further optimization of switching speed and modulation depth could improve the pulse extraction efficiency and the proposed structure can be readily applied in all-fiber Q-switching laser systems for marking applications.
A new type of novel all-fiber power splitter has been designed and experimentally demonstrated, which could be directly applied to very short reach (VSR) passive optical networks (PON) based on hard polymer clad fibers (HPCF). Overcoming silica glass manufacturing difficulties, we successfully developed a 4x4 HPCF star coupler using a micro hydrogen-burner flame brushing. The device showed an excellent uniformity in power splitting ratio along with a very low excess loss of 4.58dB and insertion loss of 10.5dB over a wide wavelength range 600-900nm. Transmission quality and power budget for PON using the devices were analyzed for 1.25 and 2.5Gbps at 10, 25, 50m, whose results confirmed highly practical potential of the proposed device in VSR PON systems with a reasonable power budget.
We present a novel micro optical waveguide (MOW) on micro actuating platform (MAP) structure that is used for a variable optical attenuator. The device is consists of a fused biconical taper (FBT) coupler mounted on an electromechanical system where an axial stress over the waist of FBT coupler is precisely controlled. Its operation is based on change of coupling constant by compressive stress induced photoelastic effects on the waist zone. We use two FBT couplers to implement an enhanced performance of variable optical attenuator. The couplers are made from a standard single mode fiber and have a circular cross-section in their waist with an enough heating temperature. Each FBT coupler is optimized at 1450nm where total insertion loss is 0.75dB. π phase shifts in the coupling constant have been observed at an axial displacement of 9.5μm. The spectral response between two output ports of the coupler is reciprocal. This allows the proposed device to achieve a high attenuation of >72dB and for 20dB attenuation a flat bandwidth of <1dB over 100nm. Both a low polarization dependent loss (PDL) of <0.07dB and a low operating voltage of 15.3V have been demonstrated with a micro-order actuation.