Garden & Greenhouse October 2018 Issue | Page 18

a building. These three vital components are the collector,
the fiber optic cables, and the cable terminal or
light fitting.
The Collector
The collector of a fiber optic lighting system is
the component that is placed directly in the sunlight
(typically on the roof of the building). As its name suggests,
the collector “collects” solar radiation and directs
it into the fiber optic cables for redistribution. One
very important component of the collector is the lens.
In a way that is similar to a magnifying glass concentrating
solar radiation, a lens on the collector concentrates
solar radiation and aims it into the fiber optic
cables. In order to maintain consistent light levels, the
collector system needs to follow the movement of the
sun. Collectors can be equipped with an internal clock
mechanism, a photo-sensor, and a microprocessor
which all work together to calculate the position of the
sun and automatically adjust the angle of the collector
for maximum light collection.
The Fiber Optic Cables
The fiber optic cables are the pathways for the radiant
energy to travel into the building. The length of
the cable, the wavelength of the light, and the quality
of the cable itself all play significant roles in the loss of
radiant energy during transmission. Fiber optic cables
are extremely efficient and do not cause a large loss of
radiant energy (light). However, to minimize light loss,
it would be best to use the shortest length of the highest
quality cables.
The Cable Terminal or Light Fitting
The cable terminal, or light fitting, is the component
that distributes the light from within the fiber
optic cable to the interior of the garden space. The
light fitting(s) can consist of a series of different light
diffusers or lenses which appear similar to conventional
lighting fixtures. For indoor horticulture applications,
a light fitting that most efficiently and evenly
diffuses the sunlight would be most applicable. Depending
on the size of the collector and the configuration
of the fiber optic cables, multiple light fittings can
be illuminated from a single collector.
Daily Light Integrals (DLI) for Greenhouses
Fiber optics could revolutionize indoor horticulture,
but would do very little for greenhouse growers
who already have access to the sun. However, many
greenhouse growers rely on artificial light systems for
supplemental light to extend the growing season and/
or maximize their return on investment. Recent advancements
in lighting automation allow greenhouse
horticulturists to maximize the efficiency of their given
supplemental lighting systems and provide the optimal
amount of light for any given crop. All varieties
of plants or crops have an ideal daily light integral, or
DLI. The term “daily light integral” refers to the actual
number of light particles (photons) received during a
24 hour period at a given location. By using a sophisticated
lighting monitor and control system, greenhouse
horticulturists can actually program a desired DLI for
a crop. The monitor will trigger a lighting controller
to turn on, off, or even dim the supplemental artificial
lighting system as needed. These sophisticated greenhouse
light monitor/controllers actually measure the
intensity of the light and can, almost intuitively, control
the artificial light system for the most effective combination
of sunlight and artificial lighting.
The future of artificial lighting in horticulture is
unknown. The sun is the pinnacle of radiant energy for
plants and matching its power will always be a white
whale for horticultural lighting system manufacturers.
The use of solar radiation via fiber optics would change
the way we view lighting for indoor gardening. When
the cost of the collection and distribution systems for
fiber optics becomes viable, fiber optics will become a
revolutionary technology for indoor gardeners.
Until then, double ended HIDs, ceramic metal
halides, and COB LEDs are the technologies that will
shape the future of indoor growing. These efficient
technologies will also shape the future of artificial
lighting for greenhouses. Efficient artificial horticultural
lighting systems teamed with sophisticated automation