Wasatch Photonics: Highest performance diffraction gratings

Dense Wavelength Division Multiplexing (DWDM):
Advanced Dickson® Gratings & Volume Phase
Holographic (VPH) Transmission Gratings

Graphs & Diagrams of DWDM Gratings (bottom of this page)
DWDM Dickson ® Grating White Paper
European Conference on Optical Communications (ECOC)

"Spectral Filter with Independently Variable Center Wavelength and Bandwidth"

by Gordon Wilson, Chien-Jen Chen, Phil Gooding, and Joe Ford
PDL & IL (dB) to Efficiency Percentage Conversion
Products | Gratings: This web page has a complete listing of high performance gratings we make along links to graphs of S & P diffraction efficiencies, dispersion, Bragg Angle sensitivity, and PDL where applicable.
Telcordia Compliance: Phone or email for additional information.
Tunable Dickson® Gratings for Agile Networks: Phone or email for additional information.

Description
Dickson® Gratings are advanced forms of VPH gratings. Many DWDM devices and subsystems vendors can utilize Volume Phase Holographic Gratings (VPHGs) for their dispersive optical platforms. These applications are shown by the green colored devices in the diagram below.

Dickson® and VPH Grating Benefits for DWDM Customers
	Dickson® Gratings	Surface Relief Gratings	Thin Film & Fiber Bragg	AWG
Hi-Channel Counts	Yes: 80+	Yes: 80+	No: < 32	Yes: up to 40
Cost/Channel	Very Low	Low	Higher	Low
Thermal Stability	A-Thermal	Maybe	A-Thermal	Requires Controls
Hi-Channel Performance	Low IL , Low PDL	Med. IL & PDL	NA	Higher IL & PDL
Channel Separation Method	Parallel	Parallel	Serial	Parallel
Footprint Size	Very Small	Very Small	Large	Small
Packaging Ease	Good	Good	Good	Medium
Integration Ease	Good	Good	Medium	Good
Agile Wavelength Tunability	Yes	No	No	No
Basic Technology >25 Years Old	Yes	Yes	Yes/No	No
Rugged, Scratch Resistant	Yes	No	Yes	Yes

DWDM systems transmit and receive multiple signals over a fiberoptic network. Each signal, containing separate data streams, is assigned to a different wavelength of laser light. This leverages the existing fiberoptic infrastructure by multiplying the amount of information that can be sent, thereby providing a migration path for telecom companies.

	DWDM Multiplexer (Mux): A transmitter that combines (multiplexes) many laser light signals of different wavelengths coming from individual glass fibers and inputs them into an optical fiber transmission line. This can also be performed through free space, without fiberoptic lines.
	DWDM Demultiplexer (DeMux): A receiver that separates (demultiplexes) many laser light signals of different wavelengths coming from an optical fiber transmission line and outputs them into individual glass fibers. This can also be performed through free space, without fiberoptic lines.
	Dynamic Gain Equalizer (DGE): DGEs correct the power imbalance in multiple channels, through user-selectable criteria, and without bit-stream interruption. To ensure low data-error rates, it is critical that all DWDM channels have approximately the same power level.
	Optical Channel Monitor (OCM): A spectrometer module for identifying DWDM channels along with measurements of wavelength, power, and OSNR (Optical Signal to Noise Ratio).
	Optical Add/Drop Multiplexer (OADM): A switching/routing device that adds and drops multiple wavelengths at various locations along an optical network.
	Reconfigurable Optical Add/Drop Multiplexer (R-OADM): A dynamically configurable switching/routing device that adds and drops multiple wavelengths at various locations along an optical network.

VPHGs Benefits

	Low Polarization Dependent Loss (PDL): over 40 nm C, S, or L Bands
	Low Insertion Loss (IL): over 40 nm C, S, or L Bands; reduced need for EDFAs
	Higher Channel Counts: high dispersion enables 40, 80, & 160 channels with close channel spacing (25, 50, & 100 GHz)
	Smaller Package: high dispersion enables small footprint
	Wider Usable Bandwidth: flat response allows increase in usable operating wavelength ranges

	Lower System Costs: extremely low pdl, low IL, a-thermal performance, and high dispersion produces a multiplicative reduction in overall cost. Reduces EDFAs, optical parts/surfaces, and maintenance
	Scalability: large quantities made quickly
	Ease of Integration:
	Technology Maturity: >25 years
	Environmental Stability: meets Telcordia GR-1221/1209 specs. Encapsulation provides a-thermal performance over -5 to 70^oC, scratch resistance, and easy handling

Diffraction Efficiencies-S (TE) & P (TM) Polarizations Best Performance Plots
Designs below are for 1525-1565 nm CWL (center or blaze wavelength) & Spatial Frequency
Dickson Gratings® highlighted in yellow
940 lpmm Dickson grating (transmission)	1550 nm at 600 lpmm (2-pass reflection)
940 lpmm Dickson grating Double Pass
940 lpmm (tunable for agile networks)	1550 nm at 600 lpmm (transmission)
940 lpmm (2-pass reflection)	1550 nm at 300 lpmm (2-pass reflection)
These are just a few representative grating graphs. We can customize gratings for your specific needs.

We provide a high level of customer service. Additionally, we offer consulting, design, prototype, product integration, and quantity production at competitive prices. For sales info contact 435-752-4301, email us, or send us a completed Customer Grating Worksheet.

Dickson® 940 lpmm Grating: Dispersion = 3.14 degrees/40 nm

Dickson® 940 lpmm Grating (Double Pass Design): Dispersion = 6.28 degrees/40 nm
		Double Pass PDL: Measured & Theoretical
600 lpmm Volume Phase Holographic (VPH) Grating: Dispersion = 1.56 degrees/40 nm

Wasatch Photonics

Sales: 435-752-4301 · Fax: 435-752-4306
info@wasatchphotonics.com

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