Synonym configuration for multi word not working


I am facing issue with multiword synonym
Example :
test => exam is working fine but
test=> online exam is not working
to fix this i have tried adding new analyzer (standard_search_analyzer) and mapped it to unigram_tokenizer pasted below. I reindexed the content after updating new config but two word synonym search didnt work . please check if there is anything wrong with my config and let us know the procedure to update synonym config

“standard_search_analyzer”: {
“type”: “custom”,
“char_filter”: [
“tokenizer”: “unigram_tokenizer”,
“filter”: [

“unigram_tokenizer”: {
“type”: “ngram_synonym”,
“n”: “1”,
“synonyms_path”: “${fess.dictionary.path}synonym.txt”,
“dynamic_reload”: true,
“expand”: true,
“reload_interval”: “1m”

The synonym tokenizer Fess uses converts the words to one token.
So, “online exam” is one token.
It might work if you use synonym token filter.