technology / faq

Frequently Asked Questions

     

How does the Optical CrossLinks' GuideLink™ material and processing compare with other low loss polymer materials? First, other polymer materials used in waveguide applications utilize embossing or spin-coating processing techniques. Both techniques create sidewalls with uneven surfaces which contribute significantly to the entire "system loss". Optical CrossLinks' (OXL) GuideLink™ system uses a monomer diffusion process to inherently embed the waveguide structure. Our process creates loss-less sidewalls.      Second, the OXL process can match the mode-field profile to the inputs and outputs. Usually our waveguides are designed as square guides which increases the coupling efficiency from waveguide into fiber.       To compare technologies accurately, the total system loss must be calculated and measured.           Why OC GuideLink™ versus silica glass waveguides? With the drive toward data-centric networks, the demand for high volume, high performance, and low cost will rule the day. Optical CrossLinks' OC GuideLink™ solutions are ideally positioned to win in this game because they offer all these features and others such as ability to accommodate both single mode and multimode fibers, route short or long wavelength signals, integrate active and passive devices, create switches or filters, and more. OC GuideLink™ films are inherently physically compliant so they can be bent and twisted – key advantages over other silica and most other polymers (usually polyimides) that are extremely hard when cured.         How do I clean OC GuideLink™ waveguides? Petroleum ether can be used. Other common solvents such as acetone, ethanol or methanol will cause permanent degradation.         Why can OC GuideLink™ waveguides achieve a 3 mm out of plane bend radius? Because there is no residual strain in the OC GuideLink™ waveguide material, the materials can be bent to a 3 mm bend radius before inducing enough strain to cause optical losses. This result is seen for both multi-mode and single mode guides at the usual wavelengths of interest: 640, 800, 980, 1310, 1480, and 1550 nm.        To which materials can OC GuideLink™ be laminated? OC GuideLink™ has been successfully laminated to FR4 boards, ceramic, silicon wafers, GaAs, and glass with no delamination or optical performance degradation after thermal cycling. In fact, lamination to rigid structures also inhibits the absorption of water vapor by the polymer waveguides.        How close must OC GuideLink™ guides be to effect evanescent coupling? Typical spacing is 2 to 20 mm for single mode guides.       Can OC GuideLink™ tolerate solder re-flow temperatures without impairment to the optical circuits? OC GuideLink™ has been subjected to standard IR solder re-flow operation specifications (30 second dwell at 250°C) without degradation in performance. Testing has been done up to 300°C for short time periods before any optically observable damage.         Practical limitations of polymer waveguides (high loss, sensitivities to temperature, degradation over time, high crosstalk, polarization sensitivity) pervade the photonics industry. What's different about the OC GuideLink™? While it is true that polymers have higher loss than glass fiber, especially at the longer wavelengths used in telecom (1550 nm), again the parameter to be measured should be the entire system loss. Highly integrated OC GuideLink™ waveguides can be quite short (on the order of a few millimeters to centimeters) therefore the entire system loss is often less than the system it is displacing. OXL has developed packaging techniques to eliminate the absorption of water vapor which comprises most of the environmental degradation of polymers. Additionally, an OC GuideLink™ waveguide bonded to the material of interest will conform to that material's coefficient of thermal expansion thus eliminating runout over the temperature range.  Crosstalk is generally caused by scattering off sidewalls. OC GuideLink™'s loss-less sidewalls greatly decrease crosstalk, thus allowing guides to be as close as 4 mm for multimode and as close as 30 mm for singlemode.  Polarization effects are caused by anisotropic characteristics in the material, such as a stretched polymer film or pulled fiber. OC GuideLink™ is essentially isotropic and any polarization effects are not measurable.        Has OXL's technology been qualified to Telcordia (Bellcore) standards? If not, where is the company in that process? OXL does not have any product undergoing qualification against Telcordia 1209 and 1221. OC GuideLink™ packaged devices have been tested against many of the toughest Telcordia tests (such as sustained high temperature/high humidity (85°/85%RH) testing and temperature cycling from –55°C to +145°C) have been conducted and the devices have shown no observable performance degradation. OXL plans to initiate testing of product families to Telcordia in Q1 of 2001.        Are there issues with relaxation of induced poling, photochromatic damage to electro-optic chromophores, material outgassing? In its post-fabrication state, OC GuideLink™ is known (anecdotally through actual structures) to have a lifetime (nominally room temperature and humidity levels) of at least 10 years with no observable degradation. Crosslinking, post-fabrication bake-out, and bonding to specific substrate materials are the central tenants to OC GuideLink™'s long term stability and superior performance.       Poling and poling relaxation are not issues for OC GuideLink™ because this phenomena occurs only in non-linear optical materials – none of which are currently used in  OC GuideLink™.        Photorefractive or photochromatic damage is a function of optical power density within the waveguides and can be adjusted through design. Preliminary testing has indicated that high optical powers do not cause any observable degradation or non-linear behaviors. Short term dwell tests at high powers in single mode guides at 1450nm in excess of 400mW showed no degradation. Sustained power tests at 1300 nm at 100 mW in single mode guides for >250 hours without degradation were also conducted. The optical powers typically encountered in datacom and telecom applications do not pose any concerns.