I'm actually not aware of any known, significant incursions of Vikings, even as the Rus, into the Middle East or Persia Aerandir mentions records of Viking travel into the Middle East below. Additionally, Viking raiders landed on Spain, North Africa, and Sicily, which put them in contact directly with local Muslim populations. Also, Middle Eastern travelers (like, of course, ibn Fadlan) interacted directly with Viking people throughout the Viking Age.

The Vikings definitely traveled to Constantinople—there is ample literary evidence, and a runic graffito in one of the galleries of the Hagia Sophia(!)—and it's likely that most of their trade contacts with the Middle East and Persia, as for much of the rest of the European world, came through that city. Constantinople was the trade center of the region, and there the Vikings easily accessed Persian goods and Arab money; the incentive to go to, say, Baghdad (one of the other great cities, along with Cordoba), where they could neither raid nor gain from trade, was all but non-existent.

I can't answer the blacksmithing question, so hopefully there's an expert in the craft for that part.

In the pre-modern world even more than today, the presence of an object coming from [place A] in [place B] is never conclusive evidence of a direct contact. We found garnets from Sri Lanka in Merovingian jewels, and Myceanean objects in Ireland; it does not mean that Franks knew the existence of India, nor that Celtic (e: cf. /u/Aerandir) chieftains had the slightest idea of what was going on in the Aegean. Long-distance trade happened mainly through the action of many middlemen, which were generally loosely connected. A good example of this fact, which is incidentally connected with your question, is the Buddha of Helgö (Sweden), unearthed in a Viking burial, which must have been traded at least four times (India > Caliphate > Constantinople > Volga > Sweden).

Vikings serving under the Eastern Roman Empire (the varangian guard) sometimes fought with the empires' soldiers around in their middle eastern provinces, Ex. at the famous battle of Manzikert.

The middle east was known as Särkland to the vikings http://en.wikipedia.org/wiki/Serkland. Several raids took place in the Caspian sea. Ex. Ingvar den Vittfarne joined a battle serving the Georgian king as mercs. http://en.wikipedia.org/wiki/Caspian_expeditions_of_the_Rus

From my understanding of Viking swords some of the steel used to manufacture the "Ulfberht" blades came from India (though the Vikings would have acquired the raw material in Persia). This was a crucible steel (wootz steel), and both the Indians and Muslims made weapons with it. There is an article: "Crucible steel in medieval swords" by Dr. Alan Williams, in "Metals and Mines Studies in Archaeometallurgy" Edited by Susan La Niece, Duncan Hook and Paul Craddock (ISBN 978-1904982197 if you'd rather) that deals more specifically with analysis of the steel in various blades. Unfortunately I have yet to track down a copy of that book, so I don't know if it contains anything enlightening about how the fabrication process differed between regions or if it focuses exclusively on the material used in manufacture of the blades.

As a side question, what has caused you to think that pattern welding was undesirable? As a form of lamination, it can produce blades that incorporate traits from multiple types of steel, resulting in a better balance of hardness and flexibility. It may have been they didn't move from it because their experiments with mono-steel blades resulted in a worse sword than continuing forward with pattern forging.