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David Brooks
Design with a broad systemic vision
ר"ג, Israel
Freelancer
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ABOUT
The extensive experience I have gained is in the field of optical communication but now also studying the field of design of embedded systems. Trying to find projects with a light to medium level of complexity in the field of embedded systems.
LANGUAGES
Hebrew
Native or bilingual proficiency
English
Professional working proficiency
SKILL DETAILS
Prototyping & Manufacturing
250 ILS / hr
Manufacturing - Circuitry & Electrical
Circuit design and drawing using KiCad. Designing printed board circuits and sending to production and components assembly on the card. Checking design validity. Microcontroller programming.
Engineering
250 ILS / hr
Communications Engineering
Microcontroller programming like ESP32, ESP8266 and WiFi based. Or PIC or AVR controllers with peripheral components appropriate to the application.
Electrical Engineering
Electrical scheme design and PCB design and fabrication using KiCad software. Writing code in C / C ++. Simulations in PSpice and LTspice
Optical Engineering
Design of optical fiber communication photonic components. Simulations with BeamProp software
Senior Executives
300 ILS / hr
CTO
I worked as a CTO at two startup companies for 14 years. The work included optical network programming, component design, simulations in special software as well as in MATLAB, PSpice.
Technology
200 ILS / hr
Arduino & Raspberry Pie
Writing code for small projects with Arduino UNO, Pro mini and ESP32 and STM32 Blue pill using Arduino IDE. The projects includes peripherals like 433MHz TX and RX and it involved writing ISR routine for best performance.
EMPLOYMENT HISTORY
October 2001
-
October 2014
CTO
ColorChip , Yokneham, Israel- As part of my role as CTO I designed and registered patents of components manufactured by the company
1985
-
1991
Senior Engineer
Motorola Semicondutor , Ramat Gan Israel- I worked as a senior engineer in the field of VLSI at Motorola Semiconductor, which manufactured chips for the field of communications networks.
COURSES & CERTIFICATIONS
1991
C Programming language
EDUCATION
1992
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1998
PhD
Tel Aviv University- Design of electro-optical photonic circuit for fiber optic communication.
1992
-
1998
PhD
Tel Aviv University
1982
-
1984
MsC
Technion
ARMED FORCES
1974
-
1977
רס"ר
חיל חימוש- בAs part of my military service and during 20 years of reserve service, I specialized in the turret weapon systems and tank optics.
PATENTS & INVENTIONS
A WAVELENGTH FILTER
null- [001] In certain applications of optical waveguides wavelength filters are needed, for example, for the separation of channels in Wavelength Division Multiplexing (WDM) systems or for gain equalization of amplifiers. Bragg Gratings with high refractive index contrast are widely used as wavelength filters in these applications, as they consume only relatively short segment of the Waveguide and their efficiency as filters may be very high.
- [002] Bragg Gratings are based on the principle of Bragg reflection. When light propagates through periodically alternating regions of higher and lower refractive index, it is partially reflected at each interface between those regions. When the round trip of the light between two reflections is an integral number of wavelengths, all the partial reflections add up in phase, and the total reflection may be nearly 100%. For a grating period P and an average refractive index n, the reflected wavelength will be λBragg = 2nP. For other wavelengths, the out-of-phase reflections end up canceling each other, resulting in high transmission.
- [003] One drawback of Bragg Gratings as wavelength filters is that the resulting reflection spectrum suffers from large sidelobes.
- [004] Reference is now made to Fig. 1, which is an illustration of a wavelength filter grating 100 as known in the art. Grating 100 may include periodically alternating sections 30 with a first refractive index and sections 32 with a second refractive index, for example, with a constant period P. An input signal 12 may propagate through grating 100. A reflected signal 14 may include a narrow band of wavelengths around a wavelength λ which fulfill the condition λ = 2nP as described above and therefore may be reflected back from grating 100. A transmitted signal 16, including wavelengths other than λ, may be transmitted forth.
- [005] Reference is now made to Fig. 2, which is a graph 200 illustrating a possible reflection spectrum of a reflected signal 14 which may be reflected by a grating 100 as described above with reference to Fig. 1. For illustration only, the wavelength axis (which is notated with WL) is calibrated so that the point “0” indicates the wavelength λ, the point “50” indicates the wavelength λ+50[nm], the point “-50” indicates the wavelength λ-50[nm], etc. As illustrated by graph 200, the reflection spectrum of a reflection signal 14 may have large sidelobes.
- [006] In order to reduce these sidelobes, it is possible to apodize the grating by changing the grating period along the grating. However, the change in the grating period should be very delicate in order to reduce the sidelobes without damaging the quality of the filter. Currently, there is no technology which may enable such delicate changes in the grating period and the quality of the filters may decrease significantly as a result of the inaccuracy. The quality of the filter increases as the transmission of the filtered wavelength is closer to 0 and the transmission of other wavelengths is closer to 100%.
- [007] Therefore, a different kind of apodization is needed in order to reduce the sidelobes of the reflected waveguide spectrum without damaging the quality of the filter.
A METHOD FOR CONNECTING ARRAY OF OPTICAL WAVEGUIDES TO AN ARRAY OF OPTICAL FIBERS WITH VERY SMALL PITCH
null- BACKGROUND OF THE INVENTION
- [001] The use of fiber optic based communication infrastructure is rapidly evolving, dictating intensive search for fiber optical infrastructure with more rapid communication rate, having smaller volume and supporting more channels of communication. Some fields of endeavor are the FTTP (Fiber To The Premises), FTTH (Fiber To The Home), FTTC (Fiber To The Curb) and the like, dealing with equipment for distribution of fiber optic based communication from one physical channel to a plurality of physical channels. One of the network concepts for the FTTP, FTTH or FTTC is the so-called PON (Passive Optical Network). In this network configuration, the fibers are distributed from a central office to the premises, through a series of cascaded splitters, splitting one channel to a number of channels, e.g. to 128 channels.
- [002] There are several technologies to produce the splitters, like fused conical fiber splitters. Another family of splitters is based on integrated optics splitting devices based on Planar Lightwave Circuit (PLC), which perform the splitting action, and to which one input fiber is optically coupled to an input port on one side, and a plurality of fibers are optically coupled to a plurality of output ports. The plurality of output fibers may be arranged in an array. The standard pitch of the array to arrange plurality of fibers is dictated by the standard fiber diameter the nominal size of which is 125 microns. Therefore the pitch of the array is usually twice that of the fiber diameter, i.e. 250 microns or slightly larger than that of fiber diameter usually 127 microns. Fig. 1 schematically illustrates a waveguide splitting unit connected to fibers according to known art. Figs. 2A and 2B schematically illustrates two bundles of coated fibers arranged in an interlaced form according to known methods. These known solutions suffer of several drawbacks. In large count output channels devices, it dictates a PLC based device because the width of the PLC must be at least the pitch of the fiber array times the number of fibers. This in turn, reduces the number of PLC fabricated per wafer, and also naturally reduces wafer yield. Also, since the PLC becomes wide, the radii of the waveguides especially those at the extremes become very small which causes additional optical propagation loss inside the device. Therefore, the ability to reduce the width of the PLC by reducing output waveguide pitch may remove the mentioned drawbacks.
A METHOD OF PRODUCING A REFLECTING SURFACE INSIDE A SUBSTRATE
null- [001] There are various known methods to fold a beam of light, advancing in a waveguide, towards the surface of the substrate of the waveguide.
- [002] Some of the known methods use gratings on the surface of the waveguide to fold the beam of light.
- [003] Reference is now made to Fig. 1, which is a known method to fold a beam of light towards the surface of the substrate 4. An edge 2 of a substrate 4 is cut and polished to form an inclined edge 6, inclined in an angle of 45°, acting substantially as a mirror reflecting the beam of light advancing in substrate 4. A device 8 to receive the folded beam of light is mounted substantially above inclined edge 6 of the substrate. Substrate 4 is usually very thin relative to the size of device 8 and therefore the length of inclined edge 6 is usually smaller than the length of device 8. Due to the size of device 8, part of it usually protrudes out of substrate 4. Therefore, the installation of device 8 on substrate 4 is not stable. Additionally, in case that device 8 needs covering to insulate it from the environment, it is hard to assemble a cover when device 8 is positioned above inclined edge 6.
PLANAR LIGHTWAVE CIRCUIT AND A METHOD FOR ITS MANUFACTURE
null- BACKGROUND
- [002] An aspect of optical communication systems relates to connecting optical fibers to other optical components (for example transceivers comprised in the systems). Optical fibers are connected to optical components using connectors that serve to mechanically couple and align the fibers’ cores with other optical components so that light can efficiently pass between the fibers and the optical components. Various types of optical connectors and methods of connecting an optical fiber to another optical component are known.
- [003] Conventionally optical connectors are connected one to the other by positioning a protruding portion of a male connector within a compatible cavity of a matching female connector. The protruding portion of the male connector holds an optical fiber ferrule. An optical fiber ferrule is an elongated sleeve often about 1.25 to2.5 mm in external diameter surrounding a tip of an optical fiber. The ferrule provides the tip with some rigidity, and is sometimes made of ceramic (zirconia) or metal (stainless alloy). The cavity in the female connector (sometimes called “sleeve”) is normally dimensioned to accept and position the ferrule. The male and female connectors normally also comprise structural features to allow easy attachment and/or detachment one from the other and for securing them when connected in a proper position.
- [004] Some types of optical components, for example optical transceivers, are classified by a method or type of fiber connector that is used to couple the components to an optical fiber.
- [005] For example, one group of transceivers uses a method often termed a “pigtail method” for coupling fibers to the transceivers. Transceivers of this group are often referred to as pigtail transceivers. In the pigtail method one end of a short length of an optical fiber, referred to as a “pigtail”, is permanently coupled to a component of a transceiver. The other end of the fiber is usually equipped with a male connector comprising an optical fiber ferrule to be connected to a pluggable female connector.
- [006] Transceivers in a second group of transceivers, often referred to as pluggable transceivers, comprise connectors that match connectors on electronic host cards. A pluggable transceiver is attached to a host card by plugging the transceiver’s electronic connectors into the matching connectors on the card. When “plugged in”, the transceiver is connected to various electronic and/or optical components comprised in the host card. At least one of the components comprised in the card to which the transceiver is attached provides an intervening connection to an optical fiber from which the card receives and/or to which the card transmits optical signals.
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