LED Light Bulbs That Repel Bugs

Most of us are familiar with those ultraviolet bug zappers. They're not as popular as they once were but I do still see (and hear) them around on hot summer nights here in New England. 

They operate on a basic principal - bugs (mosquitos, etc) are attracted to light in the ultraviolet and visible blue/green wavelengths. Once the bugs get inside they get electrocuted by making contact with high voltage wires surrounding the light source. Most of us have probably questioned the effectiveness, wondering if more bugs are being attracted than zapped.

A group of researchers at the University of Southern California Dornsife led by Professor Travis Longcore came up with the great idea of flipping things around. In a paper published by The Royal Society last week titled Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods Longore and his group describe how to make LED bulbs that significantly reduce the amount of blue/green light and effectively repel insects. 

By mixing the right wavelengths, light can be made to still look white to humans while minimizing those attracting blue/green wavelengths, Longcore's group found that by doing this, approximately 20 percent fewer insects were attracted. Pretty cool stuff.

Longcore's group is doing additional testing and Longore is hoping they can further target specific wavelengths to repel even more of those pesky (and sometimes disease carrying) bugs away.

Wavelength Division Multiplexing (WDM)

In my last legacy Public Switched Telephone Network (PSTN) post I covered Statistical Time Division Multiplexing (STDM).  In this post let's take a look at Wavelength Division Multiplexing (WDM and DWDM) methods.

As bandwidth requirements continue to grow for both the legacy Public Switched Telephone Network and the emerged Internet/IP network most of the high bandwidth backbone transmission is being done with fiber optics and a method called Wavelength Division Multiplexing or WDM. WDM functions very similarly to Frequency Division Multiplexing (FDM). With FDM different frequencies represent different communications channels with transmission done on copper or microwaves. WDM uses wavelength instead of frequency to differentiate the different communications channels.

Wavelength

Light is sinusoidal in nature and wavelength, represented by the Greek letter lambda (λ) is a distance measurement usually expressed in meters. Wavelength  is defined as the distance in meters of one sinusoidal cycle.

Wavelength Measurement

Wavelength indicates the color of light. For example, the human eye can see light ranging in frequency from approximately 380 nm (dark violet) to approximately 765 nm (red). WDM multiplexers use wavelength, or color, of light to combine signal channels onto a single piece of optical fiber. Each WDM signal is separated by wavelength “guardbands” to protect from signal crossover. One of WDM’s biggest advantages is that it allows incoming high bandwidth signal carriers that have already been multiplexed to be multiplexed together again and transmitted long distances over one piece of fiber.

Wavelength Division Multiplexing

In addition to WDM systems engineers have developed even higher capacity Dense Wavelength Division Multiplexing (DWDM) systems. Just this past week, Cisco and US Signal announced the successful completion of the first 100 Gigabit (100G) coherent DWDM trial. As backbone bandwidth requirements continue to grow these WDM and DWDM systems are significantly reducing long haul bandwidth bottlenecks.