Edge-emitting LED Research Articles

A Data Transmission Method with Spectral Switches via Electroabsorption

In the past, the waveguide electroabsorption effect has generally been used as an intensity modulator for quasi-monochromatic light, such as lasers. Here, we study how this effect affects polychromatic light spectra. We find that for light with a Gaussian distribution spectrum, the spectral peak shift (red shift or blue shift) can be controlled by the magnitude of the applied voltage, as long as the center wavelength and the spectral band are properly selected. This result can be used as a data transmission scheme at the integrated chip level or in free space. It may offer a good option for some other light sources, such as low-cost LED or ELED (edge emitting LED), with wider spectral bandwidths.

Modelling the spectral emission of multi-section quantum dot superluminescent light-emitting diodes

By characterizing the light emission from a multi-section reconfigurable quantum dot (QD) edge-emitting LED, measured gain and unamplified spontaneous emission characteristics pertaining to the underlying gain material can be determined. This data can then be inserted into a set of equations capable of reproducing the spectral emission when the device is configured as a superluminescent diode (SLD). The accuracy of this model is validated for a highly p-doped QD multi-section LED. Excellent agreement is obtained between the model and the actual measured light output from the QD SLD.

In(Ga)As/GaAs self-organized quantum dot light emitters grown on silicon substrates

We report growth characteristics of In(Ga)As/GaAs self-organized quantum dots on Si substrates. Low temperature (17 K) photoluminescence indicates an emission peak centered at 1.057 μm having a linewidth (FWHM) of 64 meV. Atomic force microscopy (AFM) images confirm a regular array of In 0.4Ga 0.6As dots with a density of 1.2×10 11 cm −2 for 8 monolayers of growth. We have also achieved electroluminescence from edge-emitting guided-wave LED heterostructures, containing a 3–5 layer In 0.4Ga 0.6As/GaAs quantum dot active region. These devices have demonstrated maximum power outputs of 3 μW (1.4 mW) at 300 K (17 K).

Handheld digital video code distributor using edge-emitting LED's and single mode optical fibers

This paper describes a handheld bandwidth-compressed digital NTSC picture code distribution system in which circuit configurations are simplified and made more inexpensive than MPEG2 distribution systems. The proposed system is constructed using edge-emitting LEDs (ELEDs) and single-mode (SM) fibers for distributing digital NTSC picture codes so as to easily distribute video signals from a video camera to video monitors installed in a video conference hall or in locations far from the camera. Using the handheld bandwidth-compressed digital NTSC picture code distribution system, a video signal can easily be distributed to the receivers installed in places far from the sender through SM optical fibers of 10 km even if a greater number of receivers is installed in the system.

Optical fiber audio and video communication system using AOM and LED

This paper describes the construction and performance of the single-mode (SM) optical fiber communication system utilizing the acousto-optic modulator (AOM) technique for modulation of audio and video signals. An edge-emitting LED (ELED) at an optical wavelength of 1300 nm was used as a light source. The output frequency response for the direct (Oth) and diffracted (1st) beams from the AOM used together with the ELED were flat over the frequency range of 50 Hz to 6 MHz. The differential gain (DG) and differential phase (DP) of the video signal were less than 5%, and 5 degrees, respectively, and the signal-to-noise ratio (SNR) was approximately 56 dB.

New type of optical fibre analogue SSB data communication system using edge-emitting LED coupled to single-mode optical fibre

This paper describes a single-mode(SM) optical fibre SSB data communication system for use in place of power-line data transmission. In the optical transmitter, SSB data is fed through the squarewave frequency (SWFM) modulator to the edge-emitting LED (ELED) module. The light beam of the ELED module is fed to the SM optical fibre having a length of 12km. In the optical receiver, the light beam received through the SM optical fibre is detected by the PIN photodiode module, and fed to the SWFM detector to obtain the double-pulse frequency modulation (DPFM) signal voltage. The DPFM signal voltage at the output of the SWFM detector is fed to the low-pass filter (LPF) to obtain analogue SSB data. When the transmission was experimentally carried out, the spurious component was as low as −50–−70 dB and the SNR of SSB data as high as more than 65–70 dB. The optical transmitter and receiver were attached to the conventional analogue SSB data communication system to constitute a new optical fibre analogue SSB data communication system. During the field test utilizing the new system, the crosstalk and SNR were 60–70 dB and 60–70 dB on each channel, respectively. Copyright © 1999 John Wiley & Sons, Ltd.

New type of optical fibre analogue SSB data communication system using edge‐emitting LED coupled to single‐mode optical fibre

This paper describes a single-mode(SM) optical fibre SSB data communication system for use in place of power-line data transmission. In the optical transmitter, SSB data is fed through the squarewave frequency (SWFM) modulator to the edge-emitting LED (ELED) module. The light beam of the ELED module is fed to the SM optical fibre having a length of 12km. In the optical receiver, the light beam received through the SM optical fibre is detected by the PIN photodiode module, and fed to the SWFM detector to obtain the double-pulse frequency modulation (DPFM) signal voltage. The DPFM signal voltage at the output of the SWFM detector is fed to the low-pass filter (LPF) to obtain analogue SSB data. When the transmission was experimentally carried out, the spurious component was as low as −50–−70 dB and the SNR of SSB data as high as more than 65–70 dB. The optical transmitter and receiver were attached to the conventional analogue SSB data communication system to constitute a new optical fibre analogue SSB data communication system. During the field test utilizing the new system, the crosstalk and SNR were 60–70 dB and 60–70 dB on each channel, respectively. Copyright © 1999 John Wiley & Sons, Ltd.

Handheld digital video code distributor using edge-emitting LED's and single mode optical fibers

This paper describes a handheld bandwidth-compressed digital NTSC picture code distribution system in which circuit configurations are simplified and made more inexpensive than MPEG2 distribution systems. The proposed system is constructed using edge-emitting LEDs (ELEDs) and single-mode (SM) fibers for distributing digital NTSC picture codes so as to easily distribute video signals from a video camera to video monitors installed in a video conference hall or in locations far from the camera. Using the handheld bandwidth-compressed digital NTSC picture code distribution system, a video signal can easily be distributed to the receivers installed in places far from the sender through SM optical fibers of 10 km even if a greater number of receivers is installed in the system.

Compact Digital NTSC TV Signal Transmission System Using SM Optical Fibers And Its Application to Operating Status Monitoring For Laser Cutting Machine

This paper describes a compact bandwidth-compressed digital NTSC picture code transmission system in which circuit configurations are simplified and made inexpensive. The bandwidth of digital NTSC picture codes is compressed in accordance with subjective evaluation, and so the sampling rate is set at 8.13MHz (2.28×fsc) and the quantizing level at 5 bits. The frame bits for detecting the frames of picture ele-ments are generated by alternately generating 1 and 0 when the frames are specified. The proposed system is constructed using edge-emitting LED's (ELED's) and single-mode (SM) fibers for transmitting digital NTSC picture codes so as to easily distribute video signals from a video camera to video monitors. The transmitter was 80×100mm in size, 120g in weight, and 1000mw in power dissipation. The receiver was 55×120 mm in size, 100g in weight, and 800mw in power dissipation. Using the compact bandwidth-compressed digital NTSC picture code transmission system, a shot of the working pice in the laser cutting machine, as an example, was satisfactorily transmitted via SM optical fibers without noises.

通信線搬送装置を用いた双方向SM光ファイバSSBデータ通信システム

通信線搬送装置を用いた双方向SM光ファイバSSBデータ通信システム

Operation of an LED with a single-mode semiconductor amplifier as a broad-band 1.3-μm transmitter source

A semiconductor amplifier and an edge-emitting LED are operated in a single-mode-fiber connected configuration to demonstrate a broad-linewidth 1.3-/spl mu/m transmitter. The output from the LED is increased by a 13.5-dB chip gain through the amplifier to 2.3-mW while maintaining a broad 3-dB spectral width of 600 /spl Aring/ from the LED. A 600-Mb/s modulation speed was demonstrated, with open eye-patterns from the amplifier, with direct current modulation applied to the LED. A theoretical analysis shows that the LED-amplifier gain is about 7 dB less than the peak amplifier gain for a narrow-line signal due to the broad spectrum and wavelength offset of the LED. The 1.3-/spl mu/m LED-amplifier may be useful as a transmitter for fiber access networks to avoid optical beat interference noise, or as a broadband source for wavelength sliced WDM networks. The device has the potential to be monolithically integrated for wavelengths at 1.3 and 1.5 /spl mu/m. >

A four-element fiber grating sensor array with phase-sensitive detection

A four-element, time-division multiplexed, fiber grating sensor array operating between the wavelengths of 1280 and 1310 nm was constructed and tested. The array consists of a 1300-nm edge-emitting LED that illuminates four gratings spaced five meters apart. Each grating in the array reflects a spectrally narrow-band (0.3-0.5 mn) wavelength region. Measurand-induced changes in the grating period change the wavelength of the light reflected by each grating. The wavelength shifts are converted to phase changes by routing the reflected signal through a nearly path balanced fiber Mach Zehnder interferometer. The minimum detectable strain was measured to be as low as 2 nanostrain//spl radic/(Hz) for frequencies greater than 10 Hz. >

PPM versus PCM for optical local-area networks

Pulse-position modulation (PPM) is presented within the context of a local-area network (LAN) application. A simplified analysis is used to calculate the advantage of converting from pulse-code modulation (PCM) to PPM signalling in a LAN, assuming in each case the same fibre network and the same optical transmitting device. Although PPM exploits its wide bandwidth to give greater sensitivity in noise, the true system advantage is obtainable only by using a large peak-to-mean-power ratio in the transmitter. It is shown that this performance is possible for both a laser diode and for an edge-emitting LED. An experimental system is reported, operating at a data rate of 4 Mbit/s, and good correspondence with theory is obtained. Design procedures are given for broad classes of situation.

Linear InGaAsP edge-emitting LED's for single-mode fiber communications

A 1.3- mu m edge-emitting diode with a linear radiance and high coupled power into a fiber is described. The LED yields 60 mu W of coupled power into a single-mode fiber at a driving current of 100 mA and an ambient temperature of 25 degrees C. A V-groove structure with an optical absorption region separated from an active region is used. At active layer thicknesses below 0.14 mu m, linear current-light output characteristics are obtained. The spectral modulation depth is 0% over the entire emission spectral width of 75 nm, and coherence length is 22.5 mu m. LED characteristics are achieved in the range from -30 to 85 degrees C at a driving current of 100 mA. The LEDs exhibit a cutoff frequency of 250 MHz. LED reliability is discussed using results of accelerated aging carried out at the ambient temperatures of 50, 125, and 200 degrees C. The activation energy of degradation is determined to be 0.63 eV, and LED half-lives are estimated to be in excess of 10/sup 6/ h. >

Single-mode fiber WDM unit for duplex subscriber link using a substrate with embossed alignment grooves

A wavelength division multiplexing (WDM) unit for single-mode fiber (SMF) duplex transmission, with light source, photodiode (PD), and WDM coupler arranged on a common substrate, is described. Using a tolerant optical design, the optical elements, e.g. lenses and fibers, are positioned in embossed high-precision V grooves without active adjustments. Only the light source, a laser diode (LD) or an edge-emitting LED (ELED), must be aligned for optimum coupling and fixed by laser welding. Typical values of LD-to-fiber and fiber-to-PD coupling loss and crosstalk are 5 dB, 1.2 dB, and -44 dB, respectively. Hence, in spite of the potentially low-cost design, the optical performance of the device is virtually competitive with separated transmitter and receiver units. >

Al0.3Ga0.7As/Al0.05Ga0.95As light-emitting diodes on GaAs-coated Si substrates grown by liquid phase epitaxy

Al0.3Ga0.7As/Al0.05Ga0.95As double-heterostructure light-emitting diodes (LED’s) were successfully grown for the first time by liquid phase epitaxy on a GaAs-coated Si substrate that was prepared by a sequential process of migration-enhanced epitaxy and molecular beam epitaxy. The edge-emitting LED’s had diode ideality factors of 1.54 at a forward-biased voltage higher than 0.9 V and external quantum efficiencies of 3.3×10−3 W/A per facet. This efficiency is 50 times higher than the previously reported value, and is on the same order as that of AlGaAs homojunction LED’s fabricated on the GaAs substrates by liquid phase epitaxy.

Nonlinear optical properties for high-Δ, small-core single-mode fibres

Nonlinear optical properties of high- Delta , small-core single-mode fibres were investigated. Results indicated that such fibres have low stimulated Raman scattering critical powers and large frequency chirping. In addition, 43% coupling efficiency was achieved in the direct coupling between high- Delta fibres and an edge-emitting LED.

Measurement of chromatic dispersion in installed single-mode fibre

The measurement of chromatic dispersion in single-mode fibres using a 1300 nm edge-emitting LED, a 1550 nm laser diode, and the phase shift method are described. The approach is insensitive to fibre temperature change throughout the measurement, and may enable dispersion in single-mode fibre optimised for 1300 nm operation to be characterised in the 1550 nm region, as well as in the 1300 nm region. The influence of the edge-emitting LED on the measurement is also considered, in that error can arise through selecting narrow wavelength regions of its output, and matching its wavelength coverage to the fibre zero dispersion region is important for long length characterisation. Measurements on installed SM fibres are discussed.

Gigabit single-mode fiber transmission using 1.3-µm edge-emitting LEDs for broad-band subscriber loops

This paper describes gigabit single-mode fiber transmission using 1.3-μm edge-emitting LED's for broad-band subscriber loops, focusing on a method of calculation for maximum transmission distance and 1.2-Gbit/s and 600-Mbit/s transmission experiments. Gigabit single-mode fiber transmission is necessary for subscriber loops, especially in broad-band ISDN and optical CATV systems. Edgeemitting LED's are excellent light sources because of their high power launched into the fiber compared with surface-emitting LED's, and currently lower cost and higher reliability than laser diodes. The maximum transmission distance is carefully estimated by taking into account the wavelength dependence for both chromatic dispersion and loss of the single-mode fiber, and the possibility of gigabit transmission near the dispersion free wavelength 1.3 μm, is confirmed. Encouraged by the above results, we demonstrate 1.2-Gbi,t/s 10-km and 600-Mbit/s 20-km transmission experiments using a newly developed 1.3-μm edge-emitting LED and a new driver circuit with a simple response compensation circuit. These results show the proposed calculation method and the LED response compensation circuit to be powerful tools for the realization of low-cost gigabit single-mode fiber transmission using edge-emitting LED's.

Transmission at 1 Gbit/s over 7.4 km of single-mode fibre using an edge-emitting LED and PINFET receiver

Transmission at 1 Gbit/s over 7.4 km of 1300 nm optimised single-mode fibre has been demonstrated using a standard, 1300 nm edge-emitting LED with 150 MHz 3 dB bandwidth and a PINFET receiver. Computer simulation was used to accurately assess each of the system degradations: LED rise/fall, extinction ratio, dispersion penalty and receiver noise.