While I don't know much about the Jewish sources from Later Middle Ages in Europe, it is likely that European/ especially Iberian Jews (and Muslims as well) have some knowledge of their brethens at least til the Middle East/ North-Eastern African continent.

The followings three are main primary sources for the communication among the Jewish community in the Early to High Middle Ages.

• The Itinerary of Benjamin of Tudela (d. 1173): Rough Map of his Itinerary; English Translations of the Work, based on the 1907 edition. He travelled from his hometown in the Iberian Peninsula, by way of several towns in the Meditteranean region with Jewish communities, to Mosul/ Basra in now Iraq. He is also said to take a route from Arabian Gulf around the Arabian Peninsula to NW Africa (as shown in the map above), but I'm not sure how the researchers have reached agreement in this part of his journey. This recent dissertation by Freedman, submitted to the University of Manchester, shows that his work has been known and read among the Jewish as well as Christian audiences during the 14th century to well into the end of the 16th century.
• The famous Geniza documents from Cairo basically also testifies this diaspora of Jewish communities across the Meditteranean Sea [Added] in the 11th century. Goldberg's Trade and Institutions in the Medieval Mediterranean: The Geniza Merchants and their Business World, Cambridge: Cambridge UP, 2012, includes the network maps of the Geniza merchants centered around the Middle (Sicily) to the Eastern part (Egypt- Syria), based on the dense communication between the Jewish communities, often tied by the marriage. [Added]: Since the center of their economic activity, Cairo in Fatimid Egypt, was overlapped with that of Karimi Islam merchant those who was also active in the Red Sea and in Indian Ocean, so it was not so likely that the latter merchant tell something about the Eastern Jews to their Jewish neighbors, I assume.
• The third famous source for the Jewish traders across the Eurasian trading network around the end of the first millenium is Ibn Khordadbeh, a [Added] 10th-century Persian geographer's Kitab al-Masalik wal-Mamalik (Book of Roads and Kingdoms). In this work, he writes of the Radhanites, the travelling merchants those who can speak several languages from Frankish to Chinese, and they have been usually identified with some kind of Jewish origin. Literature: L. Rabinowitz, "The Routes of the Radanites." The Jewish Quarterly Review, New Ser. 35-3 (1945), pp. 251-280. (www.jstor.org/stable/1452187).

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It is perhaps important, however, to pay attention to some historical events from the 11th to the 15th century central Eurasia like the activity of the Turks, the Mongols, and further, the Black Death, primarily as inhibiting factors for the trading network as well as the communications in general. While those who lived in the westernmost part of the Eurasian Continents during the Later Middle Ages probably knew something about their brethens, it is likely that their information, based on the knowledge in the books as well as the actual contact, was not so up to date due to these historical developments. The more close scrutiny onto the reception of the itineraries like that of Benjamin of Tudela, as cited above, will perhaps shed further light for this topic.

Well, Christians expelled the Jews from France in 1394, so there wouldn't really be congregants in 1400 Paris to be aware of other communities in the first place. However, there is some really intriguing evidence from 1300s Ashkenaz (France and the Rhineland, roughly) that gets at the availability of knowledge about about faraway Jewish communities to people in the northern European backwater, if not to the accessibility of that knowledge to everyone.

First, I want to say there's plenty of evidence for Jewish travellers throughout the Middle Ages. A Jewish man named Isaac helped bring history's best elephant, Abulabaz, from Harun al-Rashid to Charlemagne!

Most immediately connected in this case, in the late medieval period there was a steady traffic between Ashkenaz, Spain, and Italy and Jerusalem--pilgrims in one direction, merchants and scholars in both. (Of these travellers, unfortunately, we only have the recorded experiences/"experiences" of European ones). There was even a whole community of French Jewish scholars settled in Jerusalem long before the final expulsion.

But okay, yeah, "They knew there were Jews in Jerusalem!" is a bit like asking someone if the American Civil War was fought in America. So let's look at the most famous medieval Jewish traveler, Benjamin of Tudela, even though he was actually from Navarre (Spain).

In the 1160s-1170s, Benjamin--about whom we know almost nothing beyond his name--completed an Ibn Battuta or Marco Polo-style journey across the tri-continental medieval world centuries before the two more famous explorers. Ben never states his purpose or goals, and the prologues where that information might be found differ between editions and were clearly added by later editors.

Unlike Ibn Battuta and Marky Mark, though, Benjamin is scrupulous to note whether a place he visits has a Jewish community, a ballpark figure of its population, and usually the name of its leader or a couple of scholars. Sometimes that's all we get:

Thence it is five days to Samarkand, which is the great city of the confines of Persia. In it live some 50,000 Israelites, and R. Obadiah the Nasi is their appointed head. Among them are wise and very rich men. (trans. Adler)

Other times we get a lengthy story like that of David Alroy of Almadia, who was "well versed in the Torah, in the Halachah, as well as in the Talmud, and in all the wisdom of the [Muslims], also in secular lierature and in the writings of magicians and soothsayers." As the legend Ben was told goes, David built himself up as a false messiah among Persian Jews in order to inspire a rebellion against the Persian king. The king, however, would have none of this, and paid David's father-in-law to assassinate him. (And you thought your holidays with the in-laws were awkward!) Then he announced he would go to war against the Jews in his territory in retaliation for the attempted insurrection, which was another way of saying, "Give me a truckload of gold as a fine." Which they did.

What we don't get is commentary from Ben on whether he knew about a particular community or not before he got there. Sometimes, as with Polo and Ibn Battuta, it's apparent he is relating a story he was told rather than speaking from firsthand experience but asking the reader to accept it as just as authoritative and "firsthand."

So Ben and his almost-contemporary Petahyah of Regensburg (sometimes written Petachia of Ratisbon) give a laundry list of non-Western European Jewish communities; in Ben's case, from Rome to Constantinople to Antioch to Baghdad to India to (maybe) China across to Ethiopia and back up (technically, down) through Egypt.

Now, like with all far-reaching European traveler-writers, some scholars have questioned whether Ben (a) visited all of the places the text says (b) visited anywhere at all. Scholars like Rolf-Peter Schmitz and Martin Jacobs offer the suggestion that Ben was more of a geographer and that the resulting text is more of a collaboration among scholars "back home." Set next to other examples of (especially) Jewish travel narratives, the Massa'ot functions like a compendium or quasi-encyclopedia of Jewish communities.

I'm not going to comment on this debate in the modern sense. However, I do want to comment on it from the medieval perspective.

Ben wasn't the only one who travelled. His travel narrative, the Massa'ot shel Rabbi Binyamin, also got around. We have manuscripts from around the European Jewish world, and the differences among early print editions (16th century) testify to the existence of even more manuscripts purchased or copied by more communities.

But the differences among them aren't just word or sentence variants. Especially in the case of the surviving Ashkenazi manuscript, the scribe (or some scribe along the way) has actually invented visits to cities in western Europe! To them, the Massa'ot was indeed the accounting of Jewish people and schools around the world. They needed to be there, too.

This, in turn, suggests that the picture of the tri-continental world crafted by Ben and his ghostwriters was the picture known by Jewish scholars in various western European cities--however "accurate" that might seem to us today.