Hitachi Cable, Ltd., is pleased to announce development of the low loss athermal arrayed waveguide grating (AWG) module. This module can be used as an optical multi/demultiplexer in dense wavelength division multiplexing (DWDM) systems for everything from metro area networks (MANs) to long-distance networks. Samples of the new AWG module will be shipped starting in April.

The spread of broadband telecommunications brings the construction of more and more high-speed, high-volume fiber-optic transmission networks using a variety of different technologies. Some of these networks use the wavelength division multiplexing (WDM) transmission system. The WDM transmission system allows many optical wavelengths to be transmitted through a single optical fiber, making possible a huge increase in transmission volume. This has made WDM technology very popular, as has the fact that using this system is more economical than adding optical fibers.

AWG is a key device for the construction of WDM systems. Hitachi Cable has long manufactured and distributed AWG optical multi/demultiplexers that make use of guided wave technology to form optical circuits on glass circuit boards. There are three different types of optical wavelength multi/demultiplexers: 1) the guided wave type, 2) the multi-layer thin filter film type, and 3) the fiber brag grating type. Guided wave multi/demultiplexers are presently able to combine or split waves into 48 channels, allowing for the construction of a system with more channels than any other type of multi/demultiplexer. However, these multi/demultiplexers require constant temperature control to ensure stability in the optical properties of the wavelengths being combined or split. This necessitates a heater, or other implement, to control temperature. In addition, there is a large insertion loss when optical signals pass through a multi/demultiplexer, so amplifiers must be added. Because of this, it is difficult to use multi/demultiplexers in MANs, which require simpler systems.

Hitachi Cable has been able to eliminate the temperature sensitivity of optical properties by filling the microscopic grooves on arrayed wave guides with an optical adhesive agent, which negates the thermal properties of the refractive index of glass. This allowed the Company to successfully develop athermal AWG in the autumn of 2000. However, there still remained the issue of lowering athermal AWG's losses before entry into the MAN market was possible.

Leveraging a newly developed etching technology that lowers losses, Hitachi Cable has been able to achieve losses of less than 3 dB. This breakthrough has allowed the Company to successfully develop the low loss athermal AWG. This in turn makes it easy for MANs to use AWG, and allows for the full deployment of AWG's multi-channel capabilities.

In addition, long-distance networks using AWG want to reduce the usage of heaters and amplifiers, meaning that their athermal and low loss needs are greater than ever. Through guided wave formation technology that makes use of proprietary core wavelength adjustment technology and the chemical vapor deposition (CVD) process, the Company has been able to achieve highly precise core wavelengths with an error of less than +/- 0.05 nm as well as low dispersal of less than +/- 10 ps/nm. These are levels heretofore impossible for athermal systems. Because of these breakthroughs, Hitachi Cable expects that low loss athermal AWG will be adopted by long-distance networks.

In addition, the product's package size has been reduced to less than half of the usual AWG, because temperature control heaters are no longer necessary. The new package measures 120mm × 70mm × 8mm. The Company expects to sell 16, 32, and 40 channel samples with 100 GHz wavelength spacing.

At this time, Hitachi Cable is hard at work on low loss athermal AWG with flat-shaped waves. The Company is also working on an athermal wavelength splitter for its existing DWDM system. We expect to begin selling samples of these products in September of this year.

Manufacturing Site for This Product:
Takasago Works
880 Isagosawa-cho
Hitachi City, Ibaraki Prefecture

Product Specifications

Item	Specification
Wavelength Spectrum	1.55 µm band
Operating Temperature	0-65 degrees.
Number of Channels	16/32/40
Insertion Loss (typ)	Less than 3dB/3.5dB/4.0dB
Wavelength Spacing	100 GHz
Total Channel Crosstalk	More than 20dB
Wavelength Dispersion	Less than +/- 10ps/nm
Core Wavelength Precision (typ)	Less than +/- 0.05nm
Size	120mm × 70mm × 8mm

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