With the continuous development and improvement of human factors lighting research, while satisfying the functional lighting of indoor spaces, people are pursuing more breakthroughs and innovations in lighting quality for health. Expanded from the traditional work surface illuminance to the spatial light distribution. This study proposed a new evaluation parameter for indoor lighting environment named as BI (Brightness Index), proposed Bav(Average Brightness) and UB(brightness uniformity) to measure the brightness and the chiaroscuro of the indoor lighting environment. Taking the classroom as an example, the accuracy and feasibility of the parameters were verified through on-site testing and simulation. Results shew the effectiveness and application potentiality in lighting design and evaluation, can well complement and improve the current lighting environment evaluation system.
This study analyzed how projection display technology affect visual comfort of art museum visitors by means of both subjective and objective experiments, with 30 participants and eye-tracker as recorder.
With the development of the city, LED street lamps on urban roads gradually come into people's vision. This paper first investigates the lighting situation in some dark places on campus. On the premise of meeting the requirements of campus lighting at night, a new anti-crime method combining crime prevention lighting and optical communication is proposed. Through the transmission of voice signals, pedestrians are reminded to enhance safety and reduce the probability of dangerous events. To solve the question of visible light sound communication based on white LEDs,a 9W white LEDcommunication system is designed which can realize 300~8000Hz sound signal transmission.Firstly,the paper gives the overall design scheme based on UART according to the requirements. Secondly, the hardware equipment is made.Finally,the program of MCU is designed.Tseting and practical application show that the communication distance is 30cm,the baud rate is 227kb/s,the sound power is 0.7w,the system reaches the design requirements
As to electromagnetic wave interfere and only one to one transmission problem of Bluetooth, a short-range LED optical wireless transmission method is proposed to be complementary technology in this paper. Furthermore achieved image transmission through this method. The system makes C52 to be the mater controller, transmitter got data from terminals by USB and sends modulated signals with LED. Optical signal is detected by PD, through amplified, filtered with shaping wave from, and demodulated on receiver. Then send to terminals like PC and reverted back to original image. Analysis the performance from peak power and average power, power consumption of transmitter, relationship of bit error rate and modulation mode, and influence of ambient light, respectively. The results shows that image can be received accurately which uses this method. The most distant transmission distance can get to 1m with transmitter LED source of 1w, and the transfer rate is 14.4Kbit/s with OOK modulation mode on stabilization system, the ambient light effect little to LED transmission system in normal light environment. The method is a convenient to carry LED wireless short range transmission for mobile transmission equipment as a supplement of Bluetooth short-range transmission for its ISM band interfere, and the analysis method in this paper can be a reference for other similar systems. It also proves the system is feasibility for next study.
Visible light communication (VLC) systems have an advantage for simultaneously achieving communication and illumination. To strengthen the performance of VLC by using RGB light-emitting diodes (LEDs) while meeting the lighting requirements, the channel capacity and the transmission capability of the system are improved by utilizing the wavelength division multiplexing (WDM) technology. We make the chromaticity of the merged white light suitable for human eyes by the experiment. The parameters of merged white light based on RGB LEDs and the merging ratio data measured by the experiment are given. Hence, we study and analyze the eye diagrams and bit error rate (BER) of different optical channels. The simulation results show that maximum transmission rate of the output signal is up to 3.3 Gbit/s, and the BER is less than 10−5 with a transmission distance of 2.5 m while meeting standard illumination requirements.
Optical Code Division Multiplex Access, OCDMA, is a kind of new technology which is combined the wireless CDMA technology and the optical fiber communication technology together. The address coding technology in OCDMA system has been researched. Besides, the principle of the codec based on optical fiber delay line and non-coherent spectral domain encoding and decoding has been introduced and analysed, and the results was verified by experiment.
Optical orthogonal frequency division multiplexing (OFDM) system combines the advantages of both wireless OFDM and optical fiber technology, thus has high spectral efficiency and can effectively resist polarization mode dispersion and chromatic dispersion in fiber link. However, high peak-to-average power ratio (PAPR) is one of the important shortcomings of optical OFDM system, which requires not only amplifiers with a greater dynamic range, but also leads to serious fiber nonlinear effect. So how to reduce PAPR of optical OFDM system is a crucial issue. This work, aiming to reduce PAPR and improving system BER, analyzes suppression technology of PAPR based on optical OFDM system. Firstly, to improve BER, we utilize Partial Transmit Sequence (PTS) algorithm which introduces phase factors b(v) multiplying IFFT converted signals and searches a b(v) which will make PAPR minimum. But this method needs much calculation. Then we exploit companding which can compress amplitude of big OFDM signals and expand small signals. Secondly, simulating the two algorithms respectively and finding two algorithms can suppress PAPR, but the effect has room for improvement. Therefore, an implementation of PTS and companding joint algorithm is proposed, then simulating this method and adding it into optical OFDM system. A system was set up, fiber length setting as 10km, utilizing a MZM modulator and a distributed feedback laser, taking 4QAM and 512points IFFT. The results show that, joint algorithm can reduce PAPR from about 12dB to 8dB, improving the problem of high PAPR, constellation convergence, enhances optical OFDM system transmission performance.
Two-photon induced fluorescence (TPIF) is the most common method to measure the TPA cross-section, this method
has advantages of high detection sensitivity based on fluorescence measurement, and also can eliminate the influences of other nonlinear beam propagation effects. However, this method requires the assumption that the fluorescence collection efficiency is equal in every measurement, this is hardly impossible for conventional setup. In this paper, the physical model of the fluorescence collecting system is established based on the experimental setup of TPIF. The simulation results indicate that the traditional fluorescence collecting device brings some unavoidable errors because of the collection coefficients are different in different times. Against to the drawback of the conventional fluorescence collection device, an improved recommendation which uses integrating sphere is presented. The analysis shows that the measurement accuracy of the two-photo absorption cross-section can be improved as the collection coefficients are same in different times.
A new naked eyes stereoscopic display optical system for multi-users was proposed in this paper, different from the
conventional naked eyes stereoscopic display monitors with sophistication technology and bad uniformity of
illumination. According to the binocular parallax technology, Fresnel lens and polaroid sheet were chosen to focus the
rays on the observers' eyes. Freeform lens were used in this system to enhance illumination uniformity of pictures and
efficiency of the system. The results of simulation showed that the users can obtain stereoscopic effect at their each
places, uniformity of illumination on LCD was above 0.6. Therefore, this system had a simple and compact structure,
and the quality of pictures users obtain was better than system without freeform lenses.
We propose a simple highly nonlinear photonic crystal fiber in optical coherence tomography window. Based on the
finite difference method, different properties of highly nonlinear photonic crystal fibers are calculated. It is
demonstrated that the nonlinear coefficients more than 64 and 55 [Wkm]-1 at 1.06 μm and 1.31 μm, respectively,
with flattened chromatic dispersion of 0 ± 3.7 ps/(nm.km) and low confinement losses less than 10-9 dB/m,
simultaneously. It is also shown that small chromatic dispersion value and nearly zero dispersion slop provide the
possibility of efficient supercontinuum generation in the optical coherence tomography window using a few ps pulses.
Polarization mode dispersion (PMD) is the differential group delay between two differently polarized modes in single mode fibers, which is a serious limiting factor for high bit rate optical telecommunication systems. In our previous work, a novel measurement method of PMD in optical fibers has been proposed, which is based on coherent optical frequency domain reflectometry technique (OFDR). In the method, a frequency-shifted feedback (FSF) fiber laser was developed as light source; PMD is determined by self-delayed heterodyne detection from the beat frequency generated by interference between lights from the Fresnel reflection at the far end of the fiber. In this work, both theoretical and experimental comparisons are made between the proposed method and other International Telecommunication Union-Telecommunication standardization (ITU-T) recommended methods. Up till now, several kinds of methods have been proposed by different groups. According to the bandwidth of light sources, however, two categories can be distinguished: narrow band (quasi-monochromatic) wavelength tunable laser and broadband sources. The characteristic of our proposed method different from the two types of source in that it utilize a FSF laser, with a bandwidth between the narrow band and broadband. We analysis the difference from the view point of laser theory, and imply the effects on PMD measurements. Also experimental comparisons are made with ITU-T PMD Round Robin samples, and experimental results verified the effectiveness of the novel OFDR technique based method.
Polarization mode dispersion (PMD) is a serious limiting factor for high bit rate optical telecommunication systems. It is important and necessary for network managers to obtain PMD information at single end of the fiber cable. In this paper, a novel measurement method of PMD in optical fibers and devices is proposed, which is based on coherent optical frequency domain reflectometry technique (OFDR). In the method, a frequency-shifted feedback (FSF) fiber laser is developed as light source; therefore a frequency chirped probe light with good linearity, wide chirp range, and high chirp rate is realized. The PMD is determined by self-delayed heterodyne detection from the beat frequency generated by interference between lights from the Fresnel reflection at the far end of the device under test, which makes the measurement at single end of the device possible. Experiment is demonstrated on both polarization maintaining fibers (PMF) and single mode fibers (SMF), and results are in agreement with interferometric method.
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